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Topics - Geoffw

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U3A Walkers / Monday Walkers Back in Action!
May 10, 2021, 08:08:03 pm
Nearly thirty Pembrokeshire U3A members met at Bosherston National Trust Car Park today to for their first walk for many, many months.

We follow the path alongside the beautiful lily ponds to Broad Haven beach, walk along the beach and up to the car park at Broad Haven before a short walk along the road to Woodlands. This took us back to the lily ponds where we follow the path on the other side via 2 bridges back to the car park.

A walk of about 3.5 miles with the weather being kind as the rain showers passed us by. An ideal first walk of the season.  Such a pity we couldn't round it off with a nice lunch.

Our thank to Richard and Irene for leading the walk and to Carol Matthew for organising it.

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Some light relief...
You Should Probably Change Your Password! | Michael McIntyre Netflix Special
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Astronomy Group / Eclipses visble from St David's
May 02, 2021, 04:54:58 pm
To visit the Website CLICK HERE
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Astronomy Group / The Night Sky in May 2021
May 02, 2021, 01:30:34 pm
The Night Sky in May 2021


Moon Photo: Geoff Winterman

It's another busy month in the night sky as the Eta Aquarid meteor shower peaks in the first week of May, Venus and Mercury adorn the western sky after sunset, and Saturn and Jupiter get closer and bigger in the pre-dawn sky. And for much of the world, a total lunar eclipse occurs during the last week of May.

Here's what to see in the night sky this month....... See attachment for details
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THE SOCIETY FOR POPULAR ASTRONOMY Electronic News Bulletin No. 540 2021 May 2

Here is the latest round-up of news from the Society for Popular Astronomy.  The SPA is arguably Britain's liveliest astronomical society, with members all over the world. We accept subscription payments online at our secure site and can take credit and debit cards. You can join or renew via a secure server or just see how much we have to offer by visiting http://www.popastro.com/

MARS COULD SUPPORT PRESENT DAY MICROBIAL LIFE
Brown University

As NASA's Perseverance rover begins its search for ancient life on the surface of Mars, a new study suggests that the Martian subsurface might be a good place to look for possible present-day life on the Red Planet. The study looked at the chemical composition of Martian meteorites -- rocks blasted off of the surface of Mars that eventually landed on Earth. The analysis determined that those rocks, if in consistent contact with water, would produce the chemical energy needed to support microbial communities similar to those that survive in the unlit depths of the Earth. Because these meteorites may be representative of vast swaths of the Martian crust, the findings suggest that much of the Mars subsurface could be habitable. In recent decades, scientists have discovered that Earth's depths are home to a vast biome that exists largely separated from the world above. Lacking sunlight, these creatures survive using the by-products of chemical reactions produced when rocks come into contact with water. One of those reactions is radiolysis, which occurs when radioactive elements within rocks react with water trapped in pore and fracture space. The reaction breaks water molecules into their constituent elements, hydrogen and oxygen. The liberated hydrogen is dissolved in the remaining groundwater, while minerals like pyrite soak up free oxygen to form sulphate minerals. Microbes can ingest the dissolved hydrogen as fuel and use the oxygen preserved in the sulphates to "burn" that fuel. In places like Canada's Kidd Creek Mine, these "sulphate-reducing" microbes have been found living more than a mile underground, in water that hasn't seen the light of day in more than a billion years.

For this new study, the researchers wanted to see if the ingredients for radiolysis-driven habitats could exist on Mars. They drew on data from NASA's Curiosity rover and other orbiting spacecraft, as well as compositional data from a suite of Martian meteorites, which are representative of different parts of the planet's crust. The researchers were looking for the ingredients for radiolysis: radioactive elements like thorium, uranium and potassium; sulphide minerals that could be converted to sulphate; and rock units with adequate pore space to trap water. The study found that in several different types of Martian meteorites, all the ingredients are present in adequate abundances to support Earth-like habitats. This was particularly true for regolith breccias -- meteorites sourced from crustal rocks more than 3.6 billion years old -- which were found to have the highest potential for life support. Unlike Earth, Mars lacks a plate tectonics system that constantly recycle crustal rocks. So these ancient terrains remain largely undisturbed. The researchers say the findings help make the case for an exploration program that looks for signs of present-day life in the Martian subsurface. Prior research has found evidence of an active groundwater system on Mars in the past, the researchers say, and there's reason to believe that groundwater exists today. One recent study, for example, raised the possibility of an underground lake lurking under the planet's southern ice cap. This new research suggests that wherever there's groundwater, there's energy for life. While there are certainly technical challenges involved in subsurface exploration, they aren't as insurmountable as people may think. A drilling operation wouldn't require "a Texas-sized oil rig," and recent advances in small drill probes could soon put the Martian depths within reach.

NEW SUPER-EARTH FOUND ORBITING RED DWARF STAR
Instituto de Astrofísica de Canarias (IAC)

In recent years there has been an exhaustive study of red dwarf stars to find exoplanets in orbit around them. These stars have effective surface temperatures between 2400 and 3700 K (over 2000 degrees cooler than the Sun), and masses between 0.08 and 0.45 solar masses. In this context, a team of researchers specializing in the search for planets around this type of stars, has discovered a super-Earth orbiting the star GJ 740, a red dwarf star situated some 36 light years from Earth. The planet orbits its star with a period of 2.4 days and its mass is around 3 times the mass of Earth. Because the star is so close to the Sun, and the planet so close to the star, this new super-Earth could be the object of future researches with very large diameter telescopes towards the end of this decade. The data also indicate the presence of a second planet with an orbital period of 9 years, and a mass comparable to that of Saturn (close to 100 Earth masses), although its radial velocity signal could be due to the magnetic cycle of the star (similar to that of the Sun), so that more data are needed to confirm that the signal is really due to a planet. The Kepler mission, recognised at one of the most successful in detecting exoplanets using the transit method (which is the search for small variations in the brightness of a star caused by the transit between it and ourselves of planets orbiting around it), has discovered a total of 156 new planets around cool stars. From its data it has been estimated that this type of stars harbours an average of 2.5 planets with orbital periods of less than 200 days. Cool stars are also an ideal target for the search for planets via the radial velocity method. This method is based on the detection of small variations in the velocity of a star due to the gravitational attraction of a planet in orbit around it, using spectroscopic observations. Since the discovery in 1998 of the first radial velocity signal of an exoplanet around a cool star, until now, a total of 116 exoplanets has been discovered around this class of stars using the radial velocity method. This detection was possible due to a six year observing campaign with HARPS-N, complemented with measurements with the CARMENES spectrograph on the 3.5m telescope at the Calar Alto Observatory (Almería) and HARPS, on the 3.6m telescope at the La Silla Observatory (Chile), as well as photometric support from the ASAP and EXORAP surveys.

HYDROXYL MOLECULE DETECTED IN EXOPLANET
Trinity College Dublin

Astronomers have detected a new chemical signature in the atmosphere of an extrasolar planet . The hydroxyl radical (OH) was found on the dayside of the exoplanet WASP-33b. This planet is a so-called 'ultra-hot Jupiter', a gas-giant planet orbiting its host star much closer than Mercury orbits the Sun and therefore reaching atmospheric temperatures of more than 2,500° C (hot enough to melt most metals). This is the first direct evidence of OH in the atmosphere of a planet beyond the Solar System. It shows not only that astronomers can detect this molecule in exoplanet atmospheres, but also that they can begin to understand the detailed chemistry of this planetary population. In the Earth's atmosphere, OH is mainly produced by the reaction of water vapour with atomic oxygen. It is a so-called 'atmospheric detergent' and plays a crucial role in the Earth's atmosphere to purge pollutant gasses that can be dangerous to life (e.g., methane, carbon monoxide). In a much hotter and bigger planet like WASP-33b, where astronomers have previously detected signs of iron and titanium oxide gas) OH plays a key role in determining the chemistry of the atmosphere through interactions with water vapour and carbon monoxide. Most of the OH in the atmosphere of WASP-33b is thought to have been produced by the destruction of water vapour due to the extremely high temperature.

To make this discovery, the team used the InfraRed Doppler (IRD) instrument at the 8.2-meter diameter Subaru Telescope located in the summit area of Maunakea in Hawai`i (about 4,200 m above sea level). This new instrument can detect atoms and molecules through their 'spectral fingerprints", unique sets of dark absorption features superimposed on the rainbow of colours (or spectrum) that are emitted by stars and planets. As the planet orbits its host star, its velocity relative to the Earth changes with time. Just like the siren of an ambulance or the roar of a racing car's engine changes pitch while speeding past us, the frequencies of light (e.g., colour) of these spectral fingerprints change with the velocity of the planet. This allows astronomers to separate the planet's signal from its bright host star, which normally overwhelms such observations, despite modern telescopes being nowhere near powerful enough to take direct images of such 'hot Jupiter' exoplanets. By taking advantage of the unique capabilities of IRD, the astronomers were able to detect the tiny signal from hydroxyl in the planet's atmosphere. While WASP-33b may be a giant planet, these observations are the testbed for the next-generation facilities like the Thirty Meter Telescope and the European Extremely Large Telescope in searching for biosignatures on smaller and potentially rocky worlds, which might provide hints to one of the oldest questions of humankind: 'Are we alone?'

RCW 120 NEBULA IS YOUNGER THAN BELIEVED
West Virginia University

In the southern sky, situated about 4,300 light years from Earth, lies RCW 120, an enormous glowing cloud of gas and dust. This cloud, known as an emission nebula, is formed of ionized gases and emits light at various wavelengths. An international team of researchers studied RCW 120 to analyze the effects of stellar feedback, the process by which stars inject energy back into their environment. Their observations showed that stellar winds cause the region to expand rapidly, which enabled them to constrain the age of the region. These findings indicate that RCW 120 must be less than 150,000 years old, which is very young for such a nebula. About seven light years from the centre of RCW 120 lies the boundary of the cloud, where a plethora of stars are forming. How are all of these stars being formed? To answer that question, we need to dig deep into the origin of the nebula. RCW 120 has one young, massive star in its centre, which generates powerful stellar winds. The stellar winds from this star are much like those from our own Sun, in that they throw material out from their surface into space. This stellar wind shocks and compresses the surrounding gas clouds. The energy that is being input into the nebula triggers the formation of new stars in the clouds, a process known as "positive feedback" because the presence of the massive central star has a positive effect on future star formation. The team used SOFIA (the Stratospheric Observatory for Infrared Astronomy) to study the interactions of massive stars with their environment.

SOFIA is an airborne observatory consisting of a 2.7-metre telescope carried by a modified Boeing 747SP aircraft. SOFIA observes in the infrared regime of the electromagnetic spectrum, which is just beyond what humans can see. For observers on the ground, water vapour in the atmosphere blocks much of the light from space that infrared astronomers are interested in measuring. However, its cruising altitude of 13 km puts SOFIA above most of the water vapour, allowing researchers to study star-forming regions in a way that would not be possible from the ground. Overnight, the in-flight observatory observes celestial magnetic fields, star-forming regions (like RCW 120), comets and nebulae. Thanks to the new upGREAT receiver that was installed in 2015, the airborne telescope can make more precise maps of large areas of the sky than ever before. The research team opted to observe the spectroscopic [CII] line with SOFIA, which is emitted from diffuse ionized carbon in the star-forming region. Using their [CII] observations from SOFIA, the research team found that RCW 120 is expanding at 15 km/s, which is incredibly fast for a nebula. From this expansion speed, the team was able to put an age limit on the cloud and found that RCW 120 is much younger than previously believed. With the age estimate, they were able to infer the time it took for the star formation at the boundary of the nebula to kick in after the central star had been formed. These findings suggest that positive feedback processes occur on very short timescales and point to the idea that these mechanisms could be responsible for the high star formation rates that occurred during the early stages of the Universe.

NEW ALL-SKY MAP OF MILKY WAY'S OUTER REACHES
NASA/Jet Propulsion Laboratory

Astronomers using data from NASA and ESA (European Space Agency) telescopes have released a new all-sky map of the outermost region of our galaxy. Known as the galactic halo, this area lies outside the swirling spiral arms that form the Milky Way's recognizable central disk and is sparsely populated with stars. Though the halo may appear mostly empty, it is also predicted to contain a massive reservoir of dark matter, a mysterious and invisible substance thought to make up the bulk of all the mass in the Universe. The data for the new map comes from ESA's Gaia mission and NASA's Near Earth Object Wide Field Infrared Survey Explorer, or NEOWISE, which operated from 2009 to 2013 under the moniker WISE. The study makes use of data collected by the spacecraft between 2009 and 2018. The new map reveals how a small galaxy called the Large Magellanic Cloud (LMC) -- so named because it is the larger of two dwarf galaxies orbiting the Milky Way -- has sailed through the Milky Way's galactic halo like a ship through water, its gravity creating a wake in the stars behind it. The LMC is located about 160,000 light-years from Earth and is less than one-quarter the mass of the Milky Way. Though the inner portions of the halo have been mapped with a high level of accuracy, this is the first map to provide a similar picture of the halo's outer regions, where the wake is found -- about 200,000 light-years to 325,000 light-years from the galactic centre. Previous studies have hinted at the wake's existence, but the all-sky map confirms its presence and offers a detailed view of its shape, size, and location. This disturbance in the halo also provides astronomers with an opportunity to study something they can't observe directly: dark matter. While it doesn't emit, reflect, or absorb light, the gravitational influence of dark matter has been observed across the Universe. It is thought to create the scaffolding on which galaxies are built, such that without it, galaxies would fly apart as they spin. Dark matter is estimated to be five times more common in the Universe than all the matter that emits and/or interacts with light, from stars to planets to gas clouds.

Although there are multiple theories about the nature of dark matter, all of them indicate that it should be present in the Milky Way's halo. If that's the case, then as the LMC sails through this region, it should leave a wake in the dark matter as well. The wake observed in the new star map is thought to be the outline of this dark matter wake; the stars are like leaves on the surface of this invisible ocean, their position shifting with the dark matter. The interaction between the dark matter and the Large Magellanic Cloud has big implications for our galaxy. As the LMC orbits the Milky Way, the dark matter's gravity drags on the LMC and slows it down. This will cause the dwarf galaxy's orbit to get smaller and smaller, until the galaxy finally collides with the Milky Way in about 2 billion years. These types of mergers might be a key driver in the growth of massive galaxies across the Universe. In fact, astronomers think the Milky Way merged with another small galaxy about 10 billion years ago. The authors of the paper also think the new map -- along with additional data and theoretical analyses -- may provide a test for different theories about the nature of dark matter, such as whether it consists of particles, like regular matter, and what the properties of those particles are. The team mapped the positions of over 1,300 stars in the halo. The challenge arose in trying to measure the exact distance from Earth to a large portion of those stars: It's often impossible to figure out whether a star is faint and close by or bright and far away. After identifying stars most likely located in the halo (because they were not obviously inside our galaxy or the LMC), the team looked for stars belonging to a class of giant stars with a specific light "signature" detectable by NEOWISE. Knowing the basic properties of the selected stars enabled the team to figure out their distance from Earth and create the new map. It charts a region starting about 200,000 light-years from the Milky Way's centre, or about where the LMC's wake was predicted to begin, and extends about 125,000 light-years beyond that. One model by the Arizona team, included in the new study, predicted the general structure and specific location of the star wake revealed in the new map. Once the data had confirmed that the model was correct, the team could confirm what other investigations have also hinted at: that the LMC is likely on its first orbit around the Milky Way. If the smaller galaxy had already made multiple orbits, the shape and location of the wake would be significantly different from what has been observed. Astronomers think the LMC formed in the same environment as the Milky Way and another nearby galaxy, M31, and that it is close to completing a long first orbit around our galaxy (about 13 billion years). Its next orbit will be much shorter due to its interaction with the Milky Way.

FAST-SPINNING BLACK HOLES NARROW DARK MATTER SEARCH
Massachusetts Institute of Technology

Ultralight bosons are hypothetical particles whose mass is predicted to be less than a billionth the mass of an electron. They interact relatively little with their surroundings and have thus far eluded searches to confirm their existence. If they exist, ultralight bosons such as axions would likely be a form of dark matter, the mysterious, invisible stuff that makes up 85 percent of the matter in the Universe. Now, physicists at MIT's LIGO Laboratory have searched for ultralight bosons using black holes -- objects that are mind-bending orders of magnitude more massive than the particles themselves. According to the predictions of quantum theory, a black hole of a certain mass should pull in clouds of ultralight bosons, which in turn should collectively slow down a black hole's spin. If the particles exist, then all black holes of a particular mass should have relatively low spins. But the physicists have found that two previously detected black holes are spinning too fast to have been affected by any ultralight bosons. Because of their large spins, the black holes' existence rules out the existence of ultralight bosons with masses between 1.3x10-13 electronvolts and 2.7x10-13 electronvolts -- around a quintillionth the mass of an electron. The study is also the first to use the spins of black holes detected by LIGO and Virgo, and gravitational-wave data, to look for dark matter. Ultralight bosons are being searched for across a huge range of super-light masses, from 1x10-33 electronvolts to 1x10-6 electronvolts. Scientists have so far used tabletop experiments and astrophysical observations to rule out slivers of this wide space of possible masses. Since the early 2000s, physicists proposed that black holes could be another means of detecting ultralight bosons, due to an effect known as superradiance.

If ultralight bosons exist, they could interact with a black hole under the right circumstances. Quantum theory posits that at a very small scale, particles cannot be described by classical physics, or even as individual objects. This scale, known as the Compton wavelength, is inversely proportional to the particle mass. As ultralight bosons are exceptionally light, their wavelength is predicted to be exceptionally large. For a certain mass range of bosons, their wavelength can be comparable to the size of a black hole. When this happens, superradiance is expected to quickly develop. Ultralight bosons are then created from the vacuum around a black hole, in quantities large enough that the tiny particles collectively drag on the black hole and slow down its spin. In their study, the team looked through all 45 black hole binaries reported by LIGO and Virgo to date. The masses of these black holes -- between 10 and 70 times the mass of the Sun -- indicate that if they had interacted with ultralight bosons, the particles would have been between 1x10-13 electronvolts and 2x10-11 electronvolts in mass. For every black hole, the team calculated the spin that it should have if the black hole was spun down by ultralight bosons within the corresponding mass range. From their analysis, two black holes stood out: GW190412 and GW190517. Just as there is a maximum velocity for physical objects -- the speed of light -- there is a top spin at which black holes can rotate. GW190517 is spinning at close to that maximum. The researchers calculated that if ultralight bosons existed, they would have dragged its spin down by a factor of two. The researchers also accounted for other possible scenarios for generating the black holes' large spins, while still allowing for the existence of ultralight bosons. For instance, a black hole could have been spun down by bosons but then subsequently sped up again through interactions with the surrounding accretion disk -- a disk of matter from which the black hole could suck up energy and momentum. In other words, it's unlikely that the black holes' high spins are due to an alternate scenario in which ultralight bosons also exist. Given the masses and high spins of both black holes, the researchers were able to rule out the existence of ultralight bosons with masses between 1.3x10-13 electronvolts and 2.7x10-13 electronvolts.

ROTATING INFANT GALAXY DISCOVERED WITH NATURAL COSMIC TELESCOPE
National Institutes of Natural Sciences

Using the Atacama Large Millimeter/submillimeter Array (ALMA), astronomers found a rotating baby galaxy 1/100th the size of the Milky Way at a time when the Universe was only seven percent of its present age. Thanks to assistance by the gravitational lens effect, the team was able to explore for the first time the nature of small and dark "normal galaxies" in the early Universe, representative of the main population of the first galaxies, which greatly advances our understanding of the initial phase of galaxy evolution. Many of the galaxies that existed in the early Universe were so small that their brightness is well below the limit of the current largest telescopes on Earth and in Space, making difficult to study their properties and internal structure. However, the light coming from the galaxy named RXCJ0600-z6, was highly magnified by gravitational lensing, making it an ideal target for studying the properties and structure of a typical baby galaxies. Gravitational lensing is a natural phenomenon in which light emitted from a distant object is bent by the gravity of a massive body such as a galaxy or a galaxy cluster located in the foreground. The name "gravitational lensing" is derived from the fact that the gravity of the massive object acts like a lens. When we look through a gravitational lens, the light of distant objects is intensified and their shapes are stretched. In other words, it is a "natural telescope" floating in space. The ALMA Lensing Cluster Survey (ALCS) team used ALMA to search for a large number of galaxies in the early Universe that are enlarged by gravitational lensing. Combining the power of ALMA, with the help of the natural telescopes, the researchers are able to uncover and study fainter galaxies.

Why is it crucial to explore the faintest galaxies in the early Universe? Theory and simulations predict that the majority of galaxies formed few hundred millions years after the Big-Bang are small, and thus faint. Although several galaxies in the early Universe have been previously observed, those studied were limited to the most massive objects, and therefore the less representative galaxies, in the early Universe, because of telescopes capabilities. The only way to understand the standard formation of the first galaxies, and obtain a complete picture of galaxy formation, is to focus on the fainter and more numerous galaxies. The ALCS team performed a large-scale observation program that took 95 hours, which is a long time for ALMA observations, to observe the central regions of 33 galaxy clusters that could cause gravitational lensing. One of these clusters, called RXCJ0600-2007, is located in the direction of the constellation of Lepus, and has a mass 1000 trillion times that of the Sun. The team discovered a single distant galaxy that is being affected by the gravitational lens created by this natural telescope. ALMA detected the light from carbon ions and stardust in the galaxy and, together with data taken with the Gemini telescope, determined that the galaxy is seen as it was about 900 million years after the Big Bang (12.9 billion years ago). Further analysis of these data suggested that a part of this source is seen 160 times brighter than it is intrinsically. By precisely measuring the mass distribution of the cluster of galaxies, it is possible to "undo" the gravitational lensing effect and restore the original appearance of the magnified object. By combining data from Hubble Space Telescope and the European Southern Observatory's Very Large Telescope with a theoretical model, the team succeeded in reconstructing the actual shape of the distant galaxy RXCJ0600-z6. The total mass of this galaxy is about 2 to 3 billion times that of the Sun, which is about 1/100th of the size of our own Milky Way Galaxy. What astonished the team is that RXCJ0600-z6 is rotating. Traditionally, gas in the young galaxies was thought to have random, chaotic motion. Only recently has ALMA discovered several rotating young galaxies that have challenged the traditional theoretical framework, but these were several orders of magnitude brighter (larger) than RXCJ0600-z6. When the Thirty Meter Telescope and the Extremely Large Telescope are completed, they may be able to detect clusters of stars in the galaxy, and possibly even resolve individual stars. There is an example of gravitational lensing that has been used to observe a single star 9.5 billion light-years away, and this research has the potential to extend this to less than a billion years after the birth of the Universe.



Bulletin compiled by Clive Down

(c) 2021 The Society for Popular Astronomy

The Society for Popular Astronomy has been helping beginners in amateur astronomy -- and more experienced observers -- for over 60 years. If you are not a member, you may be missing something. Membership rates are extremely reasonable, starting at just £23 a year in the UK. You will receive our bright bi-monthly magazine Popular Astronomy, help and advice in pursuing your hobby, the chance to hear top astronomers at our regular meetings, and other benefits. The best news is that you can join online right now with a credit or debit card at our lively website: www.popastro.com
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22 April. The Lyrid meteor shower peaks in the early-morning hours. This is the first significant meteor shower since the Quadrantids in early January. The Lyrids display some 15-20 meteors per hour in good conditions. The moon, just two days past first quarter, may get in the way of the faintest meteors this year.  The Lyrids trace their apparent paths back to a point between the constellations Hercules and Lyra, both of which rise in the east around midnight. They're visible all night, but you may have more luck after midnight as the Earth turns into the meteor stream. The Lyrids have made a regular appearance for at least 2,500 years, longer than any other meteor shower. They happen as Earth passes through a stream of debris left by Comet C/1861 G1 (Thatcher).
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THE SOCIETY FOR POPULAR ASTRONOMY Electronic News Bulletin No. 539 2021 April 18

Here is the latest round-up of news from the Society for Popular Astronomy.  The SPA is arguably Britain's liveliest astronomical society, with members all over the world. We accept subscription payments online at our secure site and can take credit and debit cards. You can join or renew via a secure server or just see how much we have to offer by visiting http://www.popastro.com/

SOLAR VARIABILITY LINKED TO LA NINA EVENTS
National Center for Atmospheric Research/University Corporation for Atmospheric Research

A new study shows a correlation between the end of solar cycles and a switch from El Nino to La Nina conditions in the Pacific Ocean, suggesting that solar variability can drive seasonal weather variability on Earth. If the connection holds up, it could significantly improve the predictability of the largest El Nino and La Nina events, which have a number of seasonal climate effects over land. For example, the southern United States tends to be warmer and drier during a La Nina, while the northern U.S. tends to be colder and wetter. The appearance (and disappearance) of spots on the Sun -- the outwardly visible signs of solar variability -- have been observed by humans for hundreds of years. The waxing and waning of the number of sunspots takes place over approximately 11-year cycles, but these cycles do not have distinct beginnings and endings. This fuzziness in the length of any particular cycle has made it challenging for scientists to match up the 11-year cycle with changes happening on Earth. In the new study, the researchers rely on a more precise 22-year "clock" for solar activity derived from the Sun's magnetic polarity cycle, which they outlined as a more regular alternative to the 11-year solar cycle in several companion studies published recently in peer-reviewed journals. The 22-year cycle begins when oppositely charged magnetic bands that wrap the Sun appear near the star's polar latitudes, according to their recent studies. Over the cycle, these bands migrate toward the equator -- causing sunspots to appear as they travel across the mid-latitudes. The cycle ends when the bands meet in the middle, mutually annihilating one another in what the research team calls a terminator event.
hese terminators provide precise guideposts for the end of one cycle and the beginning of the next.

The researchers imposed these terminator events over sea surface temperatures in the tropical Pacific stretching back to 1960. They found that the five terminator events that occurred between that time and November 2010 all coincided with a flip from an El Nino (when sea surface temperatures are warmer than average) to a La Nina (when the sea surface temperatures are cooler than average). The end of the most recent solar cycle -- which is unfolding now -- is also coinciding with the beginning of a La Nina event. In fact, the researchers did a number of statistical analyses to determine the likelihood that the correlation was just a fluke. They found there was only a 1 in 5,000 chance or less (depending on the statistical test) that all five terminator events included in the study would randomly coincide with the flip in ocean temperatures. Now that a sixth terminator event -- and the corresponding start of a new solar cycle in 2020 -- has also coincided with an La Nina event, the chance of a random occurrence is even more remote, the authors said. The paper does not delve into what physical connection between the Sun and Earth could be responsible for the correlation, but the authors note that there are several possibilities that warrant further study, including the influence of the Sun's magnetic field on the amount of cosmic rays that escape into the solar system and ultimately bombard Earth. However, a robust physical link between cosmic rays variations and climate has yet to be determined. If further research can establish that there is a physical connection and that changes on the Sun are truly causing variability in the oceans, then we may be able to improve our ability to predict El Nino and La Nina events.

5,000 TONS OF EXTRATERRESTRIAL DUST FALL TO EARTH ANNUALLY
CNRS

Every year, our planet encounters dust from comets and asteroids. These interplanetary dust particles pass through our atmosphere and give rise to shooting stars. Some of them reach the ground in the form of micrometeorites. An international program conducted for nearly 20 years has determined that 5,200 tons per year of these micrometeorites reach the ground. Micrometeorites have always fallen on our planet. These interplanetary dust particles from comets or asteroids are particles of a few tenths to hundredths of a millimetre that have passed through the atmosphere and reached the Earth's surface. To collect and analyse these micrometeorites, six expeditions have taken place over the last two decades in the heart of Antarctica. It is an ideal collection spot due to the low accumulation rate of snow and the near absence of terrestrial dust. These expeditions have collected enough extraterrestrial particles (ranging from 30 to 200 micrometres in size), to measure their annual flux, which corresponds to the mass accreted on Earth per square metre per year. If these results are applied to the whole planet, the total annual flux of micrometeorites represents 5,200 tons per year. This is the main source of extraterrestrial matter on our planet, far ahead of larger objects such as meteorites, for which the flux is less than ten tons per year. A comparison of the flux of micrometeorites with theoretical predictions confirms that most micrometeorites probably come from comets (80%) and the rest from asteroids. This is valuable information to better understand the role played by these interplanetary dust particles in supplying water and carbonaceous molecules on the young Earth.

ODYSSEY ORBITER MAPS MARS FOR 20 YEARS
NASA

For two decades, the longest-lived spacecraft at the Red Planet has helped locate water ice, assess landing sites, and study the planet's mysterious moons. NASA's 2001 Mars Odyssey spacecraft launched 20 years ago on April 7, making it the oldest spacecraft still working at the Red Planet. The orbiter, which takes its name from Arthur C. Clarke's classic sci-fi novel "2001: A Space Odyssey" (Clarke blessed its use before launch), was sent to map the composition of the Martian surface, providing a window to the past so scientists could piece together how the planet evolved. But it's done far more than that, uncovering troves of water ice, serving as a crucial communications link for other spacecraft, and helping to pave the way not just for safer landings but also future astronauts. Look at almost any mapping study of the Martian surface, and it probably includes Odyssey data. For many years, the most complete global maps of Mars were made using Odyssey's infrared camera, called the Thermal Emission Imaging System, or THEMIS. The camera measures the surface temperature day and night, allowing scientists to determine what physical materials, such as rock, sand, or dust, exist. Its data reveals the presence of these materials based on how they heat up or cool down over the course of a Martian day. The net effect of two decades' worth of all that mapping? Scientists haven't just used the data to map valley networks and craters, they've also been able to spot sandstone, iron-rich rocks, salts, and more - findings that help lend deeper insight to Mars' story. THEMIS has sent back more than 1 million images since it began circling Mars. The images and maps it's produced highlight the presence of hazards, such as topographic features and boulders, but they also help ensure the safety of future astronauts by showing the location of resources such as water ice. This aids the Mars science community and NASA in deciding where to send landers and rovers - including the Perseverance rover, which touched down on Feb. 18, 2021.

From early on, Odyssey has served as a long-distance call centre for NASA's rovers and landers, sending their data back to Earth as part of the Mars Relay Network. The idea of Mars relay goes back to the 1970's, when the two Viking landers sent science data and images through an orbiter back to Earth. An orbiter can carry radios or antennas capable of sending back more data than a surface spacecraft. But Odyssey made the process routine when it began conveying data to and from NASA's Spirit and Opportunity rovers. Each day, the rovers could go somewhere new and send fresh images back to Earth. Through a relay like Odyssey, scientists got more data sooner, while the public got more Mars images to be excited over. Odyssey has supported over 18,000 relay sessions. These days, it shares the communications task with NASA's Mars Reconnaissance Orbiter and MAVEN, along with the ESA (European Space Agency) Trace Gas Orbiter. Odyssey has done such a thorough job of studying the Martian surface that scientists have started turning its THEMIS camera to capture unique views of Mars' moons Phobos and Deimos. As with the Martian surface, studying each moon's thermophysics helps scientists determine the properties of materials on their surfaces. Such information can offer glimmers into their past: It's unclear whether the moons are captured asteroids or chunks of Mars, blasted off the surface by an ancient impact. Future missions, like the Japanese Space Agency's Martian Moons eXploration (MMX) spacecraft, will seek to land on these moons. In the distant future, missions might even create bases on them for astronauts. And if they do, they'll rely on data from an orbiter that began its odyssey at the start of the millennium.

X-RAYS DETECTED FROM URANUS
Harvard-Smithsonian Center for Astrophysics

Astronomers have detected X-rays from Uranus for the first time, using NASA's Chandra X-ray Observatory. This result may help scientists learn more about this enigmatic ice giant planet in our solar system. Uranus is the seventh planet from the Sun and has two sets of rings around its equator. The planet, which has four times the diameter of Earth, rotates on its side, making it different from all other planets in the solar system. Since Voyager 2 was the only spacecraft to ever fly by Uranus, astronomers currently rely on telescopes much closer to Earth, like Chandra and the Hubble Space Telescope, to learn about this distant and cold planet that is made up almost entirely of hydrogen and helium. In the new study, researchers used Chandra observations taken in Uranus in 2002 and then again in 2017. They saw a clear detection of X-rays from the first observation, just analyzed recently, and a possible flare of X-rays in those obtained fifteen years later. What could cause Uranus to emit X-rays? The answer: mainly the Sun. Astronomers have observed that both Jupiter and Saturn scatter X-ray light given off by the Sun, similar to how Earth's atmosphere scatters the Sun's light. While the authors of the new Uranus study initially expected that most of the X-rays detected would also be from scattering, there are tantalizing hints that at least one other source of X-rays is present. If further observations confirm this, it could have intriguing implications for understanding Uranus. One possibility is that the rings of Uranus are producing X-rays themselves, which is the case for Saturn's rings. Uranus is surrounded by charged particles such as electrons and protons in its nearby space environment. If these energetic particles collide with the rings, they could cause the rings to glow in X-rays. Another possibility is that at least some of the X-rays come from auroras on Uranus, a phenomenon that has previously been observed on this planet at other wavelengths.

On Earth, we can see colourful light shows in the sky called auroras, which happen when high-energy particles interact with the atmosphere. X-rays are emitted in Earth's auroras, produced by energetic electrons after they travel down the planet's magnetic field lines to its poles and are slowed down by the atmosphere. Jupiter has auroras, too. The X-rays from auroras on Jupiter come from two sources: electrons traveling down magnetic field lines, as on Earth, and positively charged atoms and molecules raining down at Jupiter's polar regions. However, scientists are less certain about what causes auroras on Uranus. Chandra's observations may help figure out this mystery. Uranus is an especially interesting target for X-ray observations because of the unusual orientations of its spin axis and its magnetic field. While the rotation and magnetic field axes of the other planets of the solar system are almost perpendicular to the plane of their orbit, the rotation axis of Uranus is nearly parallel to its path around the Sun. Furthermore, while Uranus is tilted on its side, its magnetic field is tilted by a different amount, and offset from the planet's centre. This may cause its auroras to be unusually complex and variable. Determining the sources of the X-rays from Uranus could help astronomers better understand how more exotic objects in space, such as growing black holes and neutron stars, emit X-rays.

TRIO OF FAST-SPINNING BROWN DWARFS MAY REVEAL ROTATIONAL SPEED LIMIT
ESO

Brown dwarfs, sometimes known as "failed stars," can spin at upwards of 200,000 mph, but there may be a limit to how fast they can go. Using data from NASA's Spitzer Space Telescope, scientists have identified the three fastest-spinning brown dwarfs ever found. More massive than most planets but not quite heavy enough to ignite like stars, brown dwarfs are cosmic in-betweeners. And though they aren't as well-known as stars and planets to most people, they are thought to number in the billions in our galaxy. In a new study, astronomers argue that these three rapid rotators could be approaching a spin speed limit for all brown dwarfs, beyond which they would break apart. The rapidly rotating brown dwarfs are all about the same diameter as Jupiter but between 40 and 70 times more massive. They each rotate about once per hour, while the next-fastest known brown dwarfs rotate about once every 1.4 hours and Jupiter spins once every 10 hours. Based on their size, that means the largest of the three brown dwarfs whips around at more than 360,000 kilometres per hour). Brown dwarfs, like stars or planets, are already spinning when they form. As they cool down and contract, they spin faster, just like when a spinning ice skater draws her arms into her body. Scientists have measured the spin rates of about 80 brown dwarfs, and they vary from less than two hours (including the three new entries) to tens of hours. With so much variety among the brown dwarf speeds already measured, it surprised the authors of the new study that the three fastest brown dwarfs ever found have almost the exact same spin rate (about one full rotation per hour) as each other. This cannot be attributed to the brown dwarfs having formed together or being at the same stage in their development, because they are physically different: One is a warm brown dwarf, one is cold, and the other falls between them. Since brown dwarfs cool as they age, the temperature differences suggest these brown dwarfs are different ages.

The authors aren't chalking this up to coincidence. They think the members of the speedy trio have all reached a spin speed limit, beyond which a brown dwarf could break apart. All rotating objects generate centripetal force, which increases the faster the object spins. On a carnival ride, this force can threaten to throw riders from their seats; in stars and planets, it can tear the object apart. Before a spinning object breaks apart, it will often start bulging around its midsection as it deforms under the pressure. Scientists call this oblation. Saturn, which rotates once every 10 hours like Jupiter, has a perceptible oblation. Based on the known characteristics of the brown dwarfs, they likely have similar degrees of oblation, according to the paper authors. Considering that brown dwarfs tend to speed up as they age, are these objects regularly exceeding their spin speed limit and being torn apart? In other rotating cosmic objects, like stars, there are there natural braking mechanisms that stop them from destroying themselves. It's not clear yet if similar mechanisms exist in brown dwarfs. The maximum spin rate of any object is determined not only by its total mass but by how that mass is distributed. That's why, when very rapid spin rates are involved, understanding a brown dwarf's interior structure becomes increasingly important: The material inside likely shifts and deforms in ways that could change how fast the object can spin. Similar to gas planets such as Jupiter and Saturn, brown dwarfs are composed mostly of hydrogen and helium. But they are also significantly denser than most giant planets. Scientists think the hydrogen in the core of a brown dwarf is under such tremendous pressures that it starts behaving like a metal rather than an inert gas: It has free-floating conducting electrons, much like a copper conductor. That changes how heat is conducted through the interior and with very fast spin rates, may also affect how the mass inside an astronomical object is distributed. Physicists use observations, laboratory data, and mathematics to create models of what brown dwarf interiors should look like and how they should behave, even under extreme conditions. But current models show that the maximum brown dwarf spin speed should be about 50% to 80% faster than the one-hour rotation period described in the new study. It is possible that these theories don't have the full picture yet. Some unappreciated factor may be coming into play that doesn't let the brown dwarf spin faster. Additional observations and theoretical work may yet reveal whether there's some braking mechanism that stops brown dwarfs from self-destruction and whether there are brown dwarfs spinning even faster in the darkness.

DOUBLE QUASARS IN MERGING GALAXIES
NASA/Goddard Space Flight Center

Hubble astronomers found a pair of quasars that are so close to each other they look like a single object in ground-based telescopic photos. The researchers believe the quasars are very close to each other because they reside in the cores of two merging galaxies. A quasar is a brilliant beacon of intense light from the centre of a distant galaxy that can outshine the entire galaxy. It is powered by a supermassive black hole voraciously feeding on inflating matter, unleashing a torrent of radiation. It is estimated that in the distant Universe, for every 1,000 quasars, there is one double quasar. Quasars are scattered all across the sky and were most abundant 10 billion years ago. There were a lot of galaxy mergers back then feeding the black holes. Therefore, astronomers theorize there should have been many dual quasars during that time. The observations are important because a quasar's role in galactic encounters plays a critical part in galaxy formation, the researchers say. As two close galaxies begin to distort each other gravitationally, their interaction funnels material into their respective black holes, igniting their quasars. Over time, radiation from these high-intensity "light bulbs" launch powerful galactic winds, which sweep out most of the gas from the merging galaxies. Deprived of gas, star formation ceases, and the galaxies evolve into elliptical galaxies. Astronomers have discovered more than 100 double quasars in merging galaxies so far. However, none of them is as old as the two double quasars in this study. The Hubble images show that quasars within each pair are only about 10,000 light-years apart. By comparison, our Sun is 26,000 light-years from the supermassive black hole in the centre of our galaxy. The pairs of host galaxies will eventually merge, and then the quasars also will coalesce, resulting in an even more massive, single solitary black hole.

Astronomers first needed to figure out where to point Hubble to study them. The challenge is that the sky is blanketed with a tapestry of ancient quasars that flared to life 10 billion years ago, only a tiny fraction of which are dual. It took an imaginative and innovative technique that required the help of the European Space Agency's Gaia satellite and the ground-based Sloan Digital Sky Survey to compile a group of potential candidates for Hubble to observe. The researchers then enlisted the Gaia observatory to help pinpoint potential double-quasar candidates. Gaia measures the positions, distances, and motions of nearby celestial objects very precisely. But the team devised a new, innovative application for Gaia that could be used for exploring the distant Universe. They used the observatory's database to search for quasars that mimic the apparent motion of nearby stars. The quasars appear as single objects in the Gaia data. However, Gaia can pick up a subtle, unexpected "jiggle" in the apparent position of some of the quasars it observes. The quasars aren't moving through space in any measurable way, but instead their jiggle could be evidence of random fluctuations of light as each member of the quasar pair varies in brightness. Quasars flicker in brightness on timescales of days to months, depending on their black hole's feeding schedule. This alternating brightness between the quasar pair is similar to seeing a railroad crossing signal from a distance. As the lights on both sides of the stationary signal alternately flash, the sign gives the illusion of "jiggling." When the first four targets were observed with Hubble, it revealed that two of the targets are two close pairs of quasars. Although the team is convinced of their result, they say there is a slight chance that the Hubble snapshots captured double images of the same quasar, an illusion caused by gravitational lensing. This phenomenon occurs when the gravity of a massive foreground galaxy splits and amplifies the light from the background quasar into two mirror images. However, the researchers think this scenario is highly unlikely because Hubble did not detect any foreground galaxies near the two quasar pairs. Galactic mergers were more plentiful billions of years ago, but a few are still happening today. One example is NGC 6240, a nearby system of merging galaxies that has two and possibly even three supermassive black holes. An even closer galactic merger will occur in a few billion years when our Milky Way galaxy collides with neighbouring Andromeda galaxy. The galactic tussle would likely feed the supermassive black holes in the core of each galaxy, igniting them as quasars.

CARBON'S INTERSTELLAR JOURNEY TO EARTH
University of Michigan

We are made of stardust, the saying goes, and a pair of studies finds that may be more true than we previously thought. The first study finds that most of the carbon on Earth was likely delivered from the interstellar medium, the material that exists in space between stars in a galaxy. This likely happened well after the protoplanetary disk, the cloud of dust and gas that circled our young Sun and contained the building blocks of the planets, formed and warmed up. Carbon was also likely sequestered into solids within one million years of the Sun's birth -- which means that carbon, the backbone of life on Earth, survived an interstellar journey to our planet.

Previously, researchers thought carbon in the Earth came from molecules that were initially present in nebular gas, which then accreted into a rocky planet when the gases were cool enough for the molecules to precipitate. Astronomers point out in this study that the gas molecules that carry carbon wouldn't be available to build the Earth because once carbon vaporizes, it does not condense back into a solid. Much of carbon was delivered to the disk in the form of organic molecules. Because of this, the team inferred most of Earth's carbon was likely inherited directly from the interstellar medium, avoiding vaporization entirely. To better understand how Earth acquired its carbon, astronomers estimated the maximum amount of carbon Earth could contain. To do this, they compared how quickly a seismic wave travels through the core to the known sound velocities of the core. This told the researchers that carbon likely makes up less than half a percent of Earth's mass. Understanding the upper bounds of how much carbon the Earth might contain tells the researchers information about when the carbon might have been delivered here. A planet's carbon must exist in the right proportion to support life as we know it. Too much carbon, and the Earth's atmosphere would be like Venus, trapping heat from the Sun and maintaining a temperature of about 880 degrees Fahrenheit. Too little carbon, and Earth would resemble Mars: an inhospitable place unable to support water-based life, with temperatures around minus 60.

In a second study by the same group of authors looked at how carbon is processed when the small precursors of planets, known as planetesimals, retain carbon during their early formation. By examining the metallic cores of these bodies, now preserved as iron meteorites, they found that during this key step of planetary origin, much of the carbon must be lost as the planetesimals melt, form cores and lose gas. This upends previous thinking. Most models have the carbon and other life-essential materials such as water and nitrogen going from the nebula into primitive rocky bodies, and these are then delivered to growing planets such as Earth or Mars. But this skips a key step, in which the planetesimals lose much of their carbon before they accrete to the planets. The two studies both describe two different aspects of carbon loss -- and suggest that carbon loss appears to be a central aspect in constructing the Earth as a habitable planet. Answering whether or not Earth-like planets exist elsewhere can only be achieved by working at the intersection of disciplines like astronomy and geochemistry. Over the history of our galaxy alone, rocky planets like the Earth or a bit larger have been assembled hundreds of millions of times around stars like the Sun. Can we extend this work to examine carbon loss in planetary systems more broadly? Such research will take a diverse community of scholars.

DOUBT CAST OVER 70% OF UNIVERSE COMPOSITION :
University of Copenhagen - Faculty of Science

Until now, researchers have believed that dark energy accounted for nearly 70 percent of the ever-accelerating, expanding Universe. For many years, this mechanism has been associated with the so-called cosmological constant, developed by Einstein in 1917, that refers to an unknown repellent cosmic power. But because the cosmological constant -- known as dark energy -- cannot be measured directly, numerous researchers, including Einstein, have doubted its existence -- without being able to suggest a viable alternative. In a new study a model was tested that replaces dark energy with a dark matter in the form of magnetic forces. The usual understanding of how the Universe's energy is distributed is that it consists of five percent normal matter, 25 percent dark matter and 70 percent dark energy. In the new model, the 25 percent share of dark matter is accorded special qualities that make the 70 percent of dark energy redundant. We don't know much about dark matter other than that it is a heavy and slow particle. But then researchers wondered -- what if dark matter had some quality that was analogous to magnetism in it? We know that as normal particles move around, they create magnetism. And, magnets attract or repel other magnets -- so what if that's what's going on in the Universe? That this constant expansion of dark matter is occurring thanks to some sort of magnetic force?

The question served as the foundation for the new computer model, where researchers included everything that they know about the Universe -- including gravity, the speed of the Universe's expansion and X, the unknown force that expands the Universe. They developed a model that worked from the assumption that dark matter particles have a type of magnetic force and investigated what effect this force would have on the Universe. It turns out that it would have exactly the same effect on the speed of the Universe's expansion as we know from dark energy. However, there remains much about this mechanism that has yet to be understood by the researchers. And it all needs to be checked in better models that take more factors into consideration. The team says the discovery may just be a coincidence. But if it isn't, it is truly incredible. It would change our understanding of the universe's composition and why it is expanding. As far as our current knowledge, our ideas about dark matter with a type of magnetic force and the idea about dark energy are equally wild. Only more detailed observations will determine which of these models is the more realistic.


Bulletin compiled by Clive Down

(c) 2021 The Society for Popular Astronomy

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Poet's Corner / Something to calm!
April 10, 2021, 11:01:43 am
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Hwyel Ddda Health Board wellbeing event will help us be mindful


By Megan Hunter

Running throughout May - the wellbeing event set up by the Hywel Dda Health Board charity - aims to help people embrace the longer days of summer.

It will involve participating in activities such as star-gazing, spotting wild flowers and enjoying a brew with a view - taking a flask on a walk - and making time to be mindful.

FOR MORE INFORMATION CLICK HERE
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The Night Sky This Month - April 2021
April gets underway as the brilliant constellations Taurus, Orion, and Canis Major turn to the west after sunset and
are nearly gone for the year. Early risers can see Jupiter and Saturn in pre-dawn sky. Mars lingers in the
southwestern evening sky and rivals the bright stars of Taurus and Gemini. The Lyrid meteor shower puts on a show.
Venus re-appears as the 'Evening Star' for the rest of the year. And we mark the 60th anniversary of one of the
greatest human achievements of all time. Here's what to see in the night sky this month...
DOWNLOAD THAT ATTACHMENT BELOW FOR DETAILS
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THE SOCIETY FOR POPULAR ASTRONOMY Electronic News Bulletin No. 538 2021 April 4

Here is the latest round-up of news from the Society for Popular Astronomy.  The SPA is arguably Britain's liveliest astronomical society, with members all over the world. We accept subscription payments online at our secure site and can take credit and debit cards. You can join or renew via a secure server or just see how much we have to offer by visiting http://www.popastro.com/

NIGHT SKIES ARE BRIGHTENING
RAS

Scientists have reported that artificial objects in orbit around the Earth are brightening night skies on our planet significantly more than previously understood. The research finds that the number of objects orbiting Earth could elevate the overall brightness of the night sky by more than 10 percent above natural light levels across a large part of the planet. This would exceed a threshold that astronomers set over 40 years ago for considering a location "light polluted". The work is the first to consider the overall impact of space objects on the night sky rather than the effect of individual satellites and space debris affecting astronomers' images of the night sky. The team of researchers, based at institutions in Slovakia, Spain and the US, modelled the space objects' contribution to the overall brightness of the night sky, using the known distributions of the sizes and brightnesses of the objects as inputs to the model. The study includes both functioning satellites as well as assorted debris such as spent rocket stages. While telescopes and sensitive cameras often resolve space objects as discrete points of light, low-resolution detectors of light such as the human eye see only the combined effect of many such objects. The effect is an overall increase in the diffuse brightness of the night sky, potentially obscuring sights such as the glowing clouds of stars in the Milky Way, as seen away from the light pollution of cities.

Astronomers have expressed unease in recent years about the growing number of objects orbiting the planet, particularly large fleets of communications satellites known informally as 'mega-constellations'. In addition to crowding the night sky with more moving sources of artificial light, the arrival of this technology increases the probability of collisions among satellites or between satellites and other objects, generating further debris. Recent reports sponsored by the US National Science Foundation and the United Nations Office for Outer Space Affairs identified mega-constellations as a threat to the continued utility of astronomy facilities on the ground and in low-Earth orbit. In the UK the Royal Astronomical Society has established several working groups to understand the impact of mega-constellations on optical and radio astronomical facilities used by scientists. The results imply a further brightening of the night sky proportional to the number of new satellites launched and their optical characteristics in orbit. Satellite operators like SpaceX have recently worked to lower the brightness of their spacecraft through design changes. Despite these mitigating efforts though, the collective effect of a sharp increase in the number of orbiting objects stands to change the experience of the night sky for many across the globe. The researchers hope that their work will change the nature of the ongoing dialog between satellite operators and astronomers concerning how best to manage the orbital space around the Earth.

The near-Earth object was thought to pose a slight risk of impacting Earth in 2068, but now radar observations have ruled that out. After its discovery in 2004, asteroid 99942 Apophis had been identified as one of the most hazardous asteroids that could impact Earth. But that impact assessment changed as astronomers tracked Apophis and its orbit became better determined. Now, the results from a new radar observation campaign combined with precise orbit analysis have helped astronomers conclude that there is no risk of Apophis impacting our planet for at least a century. Estimated to be about 340 metres across, Apophis quickly gained notoriety as an asteroid that could pose a serious threat to Earth when astronomers predicted that it would come uncomfortably close in 2029. Thanks to additional observations of the near-Earth object (NEO), the risk of an impact in 2029 was later ruled out, as was the potential impact risk posed by another close approach in 2036. Until this month, however, a small chance of impact in 2068 still remained.

When Apophis made a distant flyby of Earth around March 5, astronomers took the opportunity to use powerful radar observations to refine the estimate of its orbit around the Sun with extreme precision, enabling them to confidently rule out any impact risk in 2068 and long after. On April 13, 2029, the asteroid Apophis will pass less than 32,000 kilometres from our planet's surface - closer than the distance of geosynchronous satellites. During that 2029 close approach, Apophis will be visible to observers on the ground in the Eastern Hemisphere without the aid of a telescope or binoculars. It's also an unprecedented opportunity for astronomers to get a close-up view of a solar system relic that is now just a scientific curiosity and not an immediate hazard to our planet.

INTERSTELLAR COMET IS MOST PRISTINE 
ESO

New observations with the Very Large Telescope (ESO's VLT) indicate that the rogue comet 2I/Borisov, which is only the second and most recently detected interstellar visitor to our Solar System, is one of the most pristine ever observed. Astronomers suspect that the comet most likely never passed close to a star, making it an undisturbed relic of the cloud of gas and dust it formed from. 2I/Borisov was discovered in August 2019 and was confirmed to have come from beyond the Solar System a few weeks later. Astronomers used the FORS2 instrument on ESO's VLT, located in northern Chile, to study 2I/Borisov in detail using a technique called polarimetry. Since this technique is regularly used to study comets and other small bodies of our Solar System, this allowed the team to compare the interstellar visitor with our local comets. The team found that 2I/Borisov has polarimetric properties distinct from those of Solar System comets, with the exception of Hale-Bopp. Comet Hale-Bopp received much public interest in the late 1990s as a result of being easily visible to the naked eye, and also because it was one of the most pristine comets astronomers had ever seen. Prior to its most recent passage, Hale-Bopp is thought to have passed by our Sun only once and had therefore barely been affected by solar wind and radiation. This means it was pristine, having a composition very similar to that of the cloud of gas and dust it -- and the rest of the Solar System -- formed from some 4.5 billion years ago. By analysing the polarisation together with the colour of the comet to gather clues on its composition, the team concluded that 2I/Borisov is in fact even more pristine than Hale-Bopp. This means it carries untarnished signatures of the cloud of gas and dust it formed from.

Even without a space mission, astronomers can use Earth's many telescopes to gain insight into the different properties of rogue comets like 2I/Borisov. Astronomers used data from the Atacama Large Millimeter/submillimeter Array (ALMA), in which ESO is a partner, as well as from ESO's VLT, to study 2I/Borisov's dust grains to gather clues about the comet's birth and conditions in its home system. They discovered that 2I/Borisov's coma -- an envelope of dust surrounding the main body of the comet -- contains compact pebbles, grains about one millimetre in size or larger. In addition, they found that the relative amounts of carbon monoxide and water in the comet changed drastically as it neared the Sun. The team says this indicates that the comet is made up of materials that formed in different places in its planetary system. The observations suggest that matter in 2I/Borisov's planetary home was mixed from near its star to further out, perhaps because of the existence of giant planets, whose strong gravity stirs material in the system. Astronomers believe that a similar process occurred early in the life of our Solar System. While 2I/Borisov was the first rogue comet to pass by the Sun, it was not the first interstellar visitor. The first interstellar object to have been observed passing by our Solar System was ʻOumuamua, another object studied with ESO's VLT back in 2017. Originally classified as a comet, ʻOumuamua was later reclassified as an asteroid as it lacked a coma.

MARS'S WATER IS STILL TRAPPED THERE
California Institute of Technology

Billions of years ago, the Red Planet was far more blue; according to evidence still found on the surface, abundant water flowed across Mars and forming pools, lakes, and deep oceans. The question, then, is where did all that water go? The answer: nowhere. According to new research, a significant portion of Mars's water -- between 30 and 99 percent -- is trapped within minerals in the planet's crust. The research challenges the current theory that the Red Planet's water escaped into space. The team found that around four billion years ago, Mars was home to enough water to have covered the whole planet in an ocean about 100 to 1,500 metres deep; a volume roughly equivalent to half of Earth's Atlantic Ocean. But, by a billion years later, the planet was as dry as it is today. Previously, scientists seeking to explain what happened to the flowing water on Mars had suggested that it escaped into space, victim of Mars's low gravity. Though some water did indeed leave Mars this way, it now appears that such an escape cannot account for most of the water loss.

The team studied the quantity of water on Mars over time in all its forms (vapour, liquid, and ice) and the chemical composition of the planet's current atmosphere and crust through the analysis of meteorites as well as using data provided by Mars rovers and orbiters, looking in particular at the ratio of deuterium to hydrogen (D/H). Water is made up of hydrogen and oxygen: H2O. Not all hydrogen atoms are created equal, however. There are two stable isotopes of hydrogen. The vast majority of hydrogen atoms have just one proton within the atomic nucleus, while a tiny fraction (about 0.02 percent) exist as deuterium, or so-called "heavy" hydrogen, which has a proton and a neutron in the nucleus. The lighter-weight hydrogen (also known as protium) has an easier time escaping the planet's gravity into space than its heavier counterpart. Because of this, the escape of a planet's water via the upper atmosphere would leave a telltale signature on the ratio of deuterium to hydrogen in the planet's atmosphere: there would be an outsized portion of deuterium left behind. However, the loss of water solely through the atmosphere cannot explain both the observed deuterium to hydrogen signal in the Martian atmosphere and large amounts of water in the past. Instead, the study proposes that a combination of two mechanisms -- the trapping of water in minerals in the planet's crust and the loss of water to the atmosphere -- can explain the observed deuterium-to-hydrogen signal within the Martian atmosphere. When water interacts with rock, chemical weathering forms clays and other hydrous minerals that contain water as part of their mineral structure. This process occurs on Earth as well as on Mars. Because Earth is tectonically active, old crust continually melts into the mantle and forms new crust at plate boundaries, recycling water and other molecules back into the atmosphere through volcanism. Mars, however, is mostly tectonically inactive, and so the "drying" of the surface, once it occurs, is permanent.

STRATOSPHERIC WINDS ON JUPITER
ESO

Using the Atacama Large Millimeter/submillimeter Array (ALMA), a team of astronomers have directly measured winds in Jupiter's middle atmosphere for the first time. By analysing the aftermath of a comet collision from the 1990s, the researchers have revealed incredibly powerful winds, with speeds of up to 1450 kilometres an hour, near Jupiter's poles. They could represent what the team have described as a "unique meteorological beast in our Solar System". Jupiter is famous for its distinctive red and white bands: swirling clouds of moving gas that astronomers traditionally use to track winds in Jupiter's lower atmosphere. Astronomers have also seen, near Jupiter's poles, the vivid glows known as aurorae, which appear to be associated with strong winds in the planet's upper atmosphere. But until now, researchers had never been able to directly measure wind patterns in between these two atmospheric layers, in the stratosphere. Measuring wind speeds in Jupiter's stratosphere using cloud-tracking techniques is impossible because of the absence of clouds in this part of the atmosphere. However, astronomers were provided with an alternative measuring aid in the form of comet Shoemaker-Levy 9, which collided with the gas giant in spectacular fashion in 1994. This impact produced new molecules in Jupiter's stratosphere, where they have been moving with the winds ever since. A team of astronomers has now tracked one of these molecules -- hydrogen cyanide -- to directly measure stratospheric "jets" on Jupiter. Scientists use the word "jets" to refer to narrow bands of wind in the atmosphere, like Earth's jet streams.

The most spectacular result is the presence of strong jets, with speeds of up to 400 metres per second, which are located under the aurorae near the poles. These wind speeds, equivalent to about 1450 kilometres an hour, are more than twice the maximum storm speeds reached in Jupiter's Great Red Spot and over three times the wind speed measured on Earth's strongest tornadoes. The detection indicates that these jets could behave like a giant vortex with a diameter of up to four times that of Earth, and some 900 kilometres in height. The team used 42 of ALMA's 66 high-precision antennas, located in the Atacama Desert in northern Chile, to analyse the hydrogen cyanide molecules that have been moving around in Jupiter's stratosphere since the impact of Shoemaker-Levy 9. The ALMA data allowed them to measure the Doppler shift -- tiny changes in the frequency of the radiation emitted by the molecules -- caused by the winds in this region of the planet. By measuring this shift, astronomers were able to deduce the speed of the winds much like one could deduce the speed of a passing train by the change in the frequency of the train whistle. In addition to the surprising polar winds, the team also used ALMA to confirm the existence of strong stratospheric winds around the planet's equator, by directly measuring their speed, also for the first atmosphere.

WORLDS WITH UNDERGROUND OCEANS
Southwest Research Institute

One of the most profound discoveries in planetary science over the past 25 years is that worlds with oceans beneath layers of rock and ice are common in our solar system. Such worlds include the icy satellites of the giant planets, like Europa, Titan and Enceladus, and distant planets like Pluto. Scientists conclude that the prevalence of interior water ocean worlds (IWOWs) in our solar system suggests they may be prevalent in other star systems as well, vastly expanding the conditions for planetary habitability and biological survival over time. It has been known for many years that worlds like Earth, with oceans that lie on their surface, must reside within a narrow range of distances from their stars to maintain the temperatures that preserve those oceans. However, IWOWs are found over a much wider range of distances from their stars. This greatly expands the number of habitable worlds likely to exist across the galaxy. Worlds like Earth, with oceans on their exterior, are also subject to many kinds of threats to life, ranging from asteroid and comet impacts, to stellar flares with dangerous radiation, to nearby supernova explosions and more. IWOWs are impervious to such threats because their oceans are protected by a roof of ice and rock, typically several to many tens of kilometres thick, that overlie their oceans. The same layer of rock and ice that protects the oceans on IWOWs also conceals life from being detected by virtually all astronomical techniques. If such worlds are the predominant abodes of life in the galaxy and if intelligent life arises in them -- both big "ifs, -- then IWOWs may also help crack the so-called Fermi Paradox. Posed by Nobel Laureate Enrico Fermi in the early 1960s, the Fermi Paradox questions why we don't see obvious evidence of life if it's prevalent across the Universe.

RESERVOIR OF COMPLEX MOLECULES
Harvard-Smithsonian Center for Astrophysics

Scientists have discovered a vast, previously unknown reservoir of new aromatic material in a cold, dark molecular cloud by detecting individual polycyclic aromatic hydrocarbon molecules in the interstellar medium for the first time, and in doing so are beginning to answer a three-decades-old scientific mystery: how and where are these molecules formed in space? Aromatic molecules, and PAHs -- shorthand for polycyclic aromatic hydrocarbons -- are well known to scientists. Aromatic molecules exist in the chemical makeup of human beings and other animals, and are found in food and medicines. As well, PAHs are pollutants formed from the burning of many fossil fuels and are even amongst the carcinogens formed when vegetables and meat are charred at high temperatures. Polycyclic aromatic hydrocarbons are thought to contain as much as 25-percent of the carbon in the Universe. Now, for the first time, we have a direct window into their chemistry that will let us study in detail how this massive reservoir of carbon reacts and evolves through the process of forming stars and planets. Scientists have suspected the presence of PAHs in space since the 1980s but the new research, detailed in nine papers published over the past seven months, provides the first definitive proof of their existence in molecular clouds. To search out the elusive molecules, the team focused the 100m behemoth radio astronomy GBT on the Taurus Molecular Cloud, or TMC-1 -- a large, pre-stellar cloud of dust and gas located roughly 450 light-years from Earth that will someday collapse in on itself to form stars -- and what they found was astonishing: not only were the accepted scientific models incorrect, but there was a lot more going on in TMC-1 than the team could have imagined.

Previous studies revealed only that there were PAH molecules out there, but not which specific ones. Much to their surprise, the team didn't discover just one new molecule hiding out in TMC-1. Detailed in multiple papers, the team observed 1-cyanonaphthalene, 1-cyano-cyclopentadiene, HC11N, 2-cyanonaphthalene, vinylcyanoacetylene, 2-cyano-cyclopentadiene, benzonitrile, trans-(E)-cyanovinylacetylene, HC4NC, and propargylcyanide, among others. The discovery of new molecules in TMC-1 also has implications for astrochemistry, and while the team doesn't yet have all of the answers, the ramifications here, too, will last for decades. "We've gone from one-dimensional carbon chemistry, which is very easy to detect, to real organic chemistry in space in the sense that the newly discovered molecules are ones that a chemist knows and recognizes, and can produce on Earth. Before the launch of GOTHAM in 2018, scientists had catalogued roughly 200 individual molecules in the Milky Way's interstellar medium. These new discoveries have prompted the team to wonder, and rightly so, what's out there. This new aromatic chemistry that scientists are finding isn't isolated to TMC-1. A companion survey to GOTHAM, known as ARKHAM -- A Rigorous K/Ka-Band Survey Hunting for Aromatic Molecules -- recently found benzonitrile in multiple additional objects. Incredibly, benzonitrile was found in every single one of the first four objects observed by ARKHAM. This is important because while GOTHAM is pushing the limit of what chemistry we thought is possible in space, these discoveries imply that the things we learn in TMC-1 about aromatic molecules could be applied broadly to dark clouds anywhere. These dark clouds are the initial birthplaces of stars and planets. So, these previously invisible aromatic molecules will also need to be thought about at each later step along the way to the creation of stars, planets, and solar systems like our own.

STARS MISSING FROM HYADES CLUSTER
Astronomy & Astrophysics.

An invisible cosmic behemoth might be tearing apart the closest star cluster to the Sun, leaving one side of the cluster eerily dark and devoid of stars, according to a new study. The culprit may be a dark matter substructure, a relic that contains the mass of 10 million Suns and is made of a mysterious non-luminous substance. The possible presence of this "Galactic lump" was detected in a new map that charts out the enormous extent of the Hyades star cluster, located only 153 light years from Earth. Scientists came across the unnerving lump while examining the Hyades cluster using data collected by ESA's Gaia satellite. While Gaia has been able to resolve features of the Hyades cluster in unprecedented detail, the bright central region of this stellar group, which spans about 20 light years, is visible even to the naked eye. The cluster dates back some 700 million years and has changed significantly, as stars become unbound due to both interior cluster dynamics as well as gravitational forces from the larger Milky Way galaxy. These outside forces that tug at the cluster have, over the eons, sculpted two structures known as "tidal tails" that sweep out in front and behind the central hub of stars. These tails have long been observed in large stellar populations, but Hyades is the first "open" star cluster--a much smaller and younger version of these groups--that scientists have been able to pinpoint tails on. That breakthrough was published by a different team in 2019, and also relies on Gaia's advanced surveying power. Now, according to the new study, it looks like something is ripping apart one of those tails. Something we can't see. Something big. Scientists noticed this presence using the most recent Gaia data-dump in December 2020, which enabled the team to identify far-flung stars that originated within the Hyades. The researchers first produced a simulation of the cluster that predicted the current positions and velocities of stars that might have drifted out of it over time.

Because Gaia's goal is to catalogue the movement and distance of every observable star in the Milky Way, the team was then able to compare the simulation to the real data and spot the stars with trajectories and motions that matched a Hyades origin. This approach extended the known range of the two tails to an astonishing breadth of several thousand light years each. But while the simulated map of the tails predicted that they would be relatively symmetrical, the real observations showed that the trailing tail was comparatively unpopulated with stars, an asymmetry that had also been noted by the 2019 study of the cluster. The team is the first to suggest that "a close encounter with a massive Galactic lump can explain the observed asymmetry in the tidal tails of the Hyades," according to the study. Based on the observations, this lump would have to be incredibly massive and elusively hidden, because there is no sign of a visible gas cloud or star cluster that might be tugging stars off the trailing tail. To that point, the team proposes that the lurking lump may be a dark matter substructure, also known as a sub-halo. These clumps emerge in the early years of galactic formation and drift across galaxies thereafter. As the name suggests, they are made of dark matter, a non-luminous material that is far more abundant in the universe than the regular matter that makes up stars and planets. Scientists only know about dark matter because of its gravitational effects on luminous objects--potentially including, in this case, the Hyades cluster. The missing stars aren't being gobbled up, as they might be by a black hole. Rather "the orbits of the stars in the Galaxy are being affected/changed by the encounter" which may cause them to disappear from view because of the "disruption of the cluster and the tails. These sub-haloes are like smaller versions of galactic dark matter haloes, which are gargantuan structures that account for about 84 percent of the total mass of galaxies. The Milky Way's galactic halo, for instance, is estimated to be more than a trillion times more massive than the Sun, far bigger than the 10-million-Sun mass of the entity that might be causing the asymmetry in the Hyades' trailing tail. Stars that are bundled into star clusters might swap planets, or disrupt the orbits of planets in neighbouring systems, but we also shouldn't worry about that outcome because the Sun is a lonely star that left its natal cluster long ago. It's thrilling to imagine that scientists may have stumbled across such a huge and poorly understood dark matter monster, let alone one that is casually plucking stars off of the Hyades cluster. But to get a better idea of what's really going on in this cluster tail, we'll have to wait for future Gaia data releases, among other observational advances. This data will not only help to resolve the mystery of the missing stars in the Hyades, but could yield insights into other stellar and galactic enigmas as well.

EIGHT NEW MILLISECOND PULSARS
Phys.org

Pulsars are highly magnetized, rotating neutron stars emitting a beam of electromagnetic radiation. The most rapidly rotating pulsars, with rotation periods below 30 milliseconds, are known as millisecond pulsars (MSPs). Astronomers assume that they are formed in binary systems when the initially more massive component turns into a neutron star that is then spun up due to accretion of matter from the secondary star. A class of extreme binary pulsars with semi-degenerate companion stars is dubbed "spider pulsars." These objects are further categorized as "black widows" if the companion has extremely low mass (less than 0.1 solar masses), while if the secondary star is heavier, they are called "redbacks." Now, a group of astronomers report the detection of eight new MSPs, out of which five are binary systems and three turned out to be faint isolated pulsars. The discovery was made using the 64-dish MeerKAT radio telescope array in South Africa. Five new MSPs, designated 47 Tuc ac, 47 Tuc ad, NGC 6624G, M62G, and Ter 5, were found in binary systems, while the objects NGC 6522D, NGC 6624H and NGC 6752F, are faint isolated MSPs. The spin periods of the newfound pulsars are within the range from 2.74 to 8.48 ms. According to the paper, 47 Tuc ac (spin period of 2.74 ms) and 47 Tuc ad (spin period of 3.74 ms) are eclipsing "spider pulsars" with low-mass companions and regular occultations of their pulsed emission. 47 Tuc ac was found to be a "black widow" with an orbital period of about 0.18 days and a minimum companion mass of 0.0075 solar masses. With an orbital period of approximately 0.32 days and a minimum companion mass of about 0.2 solar masses, 47 Tuc ad turns out to be a "redback." Both MSPs are located in the globular cluster 47 Tuc, some 15,300 light years away from the Earth.

With a spin period at a level of 6.09 ms, NGC 6624G is a binary MSP with a highly eccentric orbit in the cluster NGC 6624. It has an orbital period 1.54 days, pulsar mass of around 2.1 solar masses and its companion is estimated to be about half as massive as the sun. The astronomers assume that the companion star could be either a massive white dwarf or a neutron star. Another MSP found in this cluster, designated NGC 6624H, is isolated and has a spin period of approximately 5.13 ms. M62G is a binary MSP with a circular orbit located in a massive cluster M62, some 22,000 light years away. It has a spin period of about 4.61 ms, orbital period of around 0.77 days and the mass of its companion is estimated to be at least 0.1 solar masses. The remaining binary MSP, designated Ter 5 an (spin period of 4.8 ms), has a slightly eccentric orbit with the longest orbital period (about 9.62 days) out of the newly detected five binary pulsars. The secondary object in this system is assumed to be a white dwarf with a minimum mass of 0.43 solar masses. The object is part of the Ter 5 globular cluster located in the galactic bulge. The isolated pulsars NGC 6522D and NGC 6752F have spin periods 5.53 ms and 8.48 ms, respectively. NGC 6522D resides in the cluster NGC 6522, which is at a distance of about 25,000 light years, close to the centre of our galaxy. When it comes to the slowest spinning object reported in the paper, it is located in a core-collapsed cluster known as NGC 6752, some 13,000 light years away.

ANCIENT LIGHT ILLUMINATES MATTER
Cornell University

Using light from the Big Bang, cosmologists have begun to unveil the material which fuels galaxy formation. Proto galaxies are always full of gas and when they cool, the galaxies start to form. If we were to just do a back-of-the-envelope calculation, gas should turn into stars but it doesn't. Galaxies are inefficient when they manufacture stars - about 10% of the gas -- at most -- in any given galaxy gets turned into stars. The scientists can now check their longtime theoretical work and simulations, by looking at microwave observations with data and applying a 1970s-era mathematical equation. They've looked at data from Atacama Cosmology Telescope (ACT) -- which observes the Big Bang's static-filled cosmic microwave background (CMB) radiation -- and search for the Sunyaev-Zel'dovich effects. That combination of data enables the scientists to map out the material around that indicate the formation of galaxies in various stages. Effectively, the scientists are using the cosmic microwave background -- remnants of the Big Bang -- as a backlit screen that is 14 billion years old to find this material around galaxies. It's like a watermark on a bank note - if you put it in front of a backlight then the watermark appears as a shadow. In this instance, the backlight is the cosmic microwave background. It serves to illuminate the gas from behind, so we can see the shadow as the CMB light travels through that gas.

FIRST IMAGES OF COSMIC WEB REVEAL DWARF GALAXIES
CNRS

Although the filaments of gas in which galaxies are born have long been predicted by cosmological models, we have so far had no real images of such objects. Now for the first time, several filaments of the 'cosmic web' have been directly observed using the MUSE instrument installed on ESO's Very Large Telescope in Chile. The filamentary structure of hydrogen gas in which galaxies form, known as the cosmic web, is one of the major predictions of the model of the Big Bang and of galaxy formation. Until now, all that was known about the web was limited to a few specific regions, particularly in the direction of quasars, whose powerful radiation acts like car headlights, revealing gas clouds along the line of sight. However, these regions are poorly representative of the whole network of filaments where most galaxies, including our own, were born. Direct observation of the faint light emitted by the gas making up the filaments was a holy grail which has now been attained by an international team of astronomers. The team took the bold step of pointing ESO's Very Large Telescope, equipped with the MUSE instrument coupled to the telescope's adaptive optics system, at a single region of the sky for over 140 hours. Together, the two instruments form one of the most powerful systems in the world. The region selected forms part of the Hubble Ultra-Deep Field, which was until now the deepest image of the cosmos ever obtained. However, Hubble has now been surpassed, since 40% of the galaxies discovered by MUSE have no counterpart in the Hubble images. After meticulous planning, it took eight months to carry out this exceptional observing campaign. This was followed by a year of data processing and analysis, which for the first time revealed light from the hydrogen filaments, as well as images of several filaments as they were one to two billion years after the Big Bang, a key period for understanding how galaxies formed from the gas in the cosmic web. However, the biggest surprise for the team was when simulations showed that the light from the gas came from a hitherto invisible population of billions of dwarf galaxies spawning a host of stars. Although these galaxies are too faint to be detected individually with current instruments, their existence will have major consequences for galaxy formation models, with implications that scientists are only just beginning to explore.

Bulletin compiled by Clive Down
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Natural History / Spring Flower Spotter
April 01, 2021, 11:25:06 am
To get a printable copy click on the image.
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Ty Canol and Pentre Ifan October 2016

To see the rest of the photographs click on the image below and then click on the thumbnails!

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Astronomy Group / In Our Time _ Eclipses
March 31, 2021, 10:43:34 am

Melvyn Bragg and guests discuss solar eclipses, some of life's most extraordinary moments, when day becomes night and the stars come out before day returns either all too soon or not soon enough, depending on what you understand to be happening. In ancient China, for example, there was a story that a dragon was eating the sun and it had to be scared away by banging pots and pans if the sun were to return. Total lunar eclipses are more frequent and last longer, with a blood moon coloured red like a sunrise or sunset. Both events have created the chance for scientists to learn something remarkable, from the speed of light, to the width of the Atlantic, to the roundness of Earth, to discovering helium and proving Einstein's Theory of General Relativity.
With
Carolin Crawford
Public Astronomer based at the Institute of Astronomy, University of Cambridge and a fellow of Emmanuel College
Frank Close
Emeritus Professor of Physics at the University of Oxford
And
Lucie Green
Professor of Physics and a Royal Society University Research Fellow at Mullard Space Science Laboratory at University College London
CLICK HERE
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SOCIETY FOR POPULAR ASTRONOMY Electronic News Bulletin No. 537 2021 March 21

Here is the latest round-up of news from the Society for Popular Astronomy.  The SPA is arguably Britain's liveliest astronomical society, with members all over the world. We accept subscription payments online at our secure site and can take credit and debit cards. You can join or renew via a secure server or just see how much we have to offer by visiting http://www.popastro.com/

ASTEROID APOPHIS FLYBY
Spaceweather.com

On April 13, 2029 asteroid 99942 Apophis will fly past Earth so close you can see it with your naked eye. In early March, Apophis made a "pre-flyby" of Earth about 16 million km away, the closest it will be before the big event in 2029. Asteroid Apophis is about 370 metres wide. That's big enough to punch through Earth's atmosphere, devastating a region the size of, say, Texas, if it hit land, or causing widespread tsunamis if it hit ocean. Fortunately, Apophis will not hit Earth in 2029. Back in 2004 when the asteroid was first discovered, astronomers thought there might be a collision. Improved observations of Apophis's orbit have since ruled out a strike. The asteroid will skim Earth's belt of geosynchronous satellites, but come no closer than 31,900 km to Earth itself. Observations in the past year have reduced the uncertainty of the flyby distance to ±20 km. At such close range, Earth's gravity could stretch the asteroid, change the way it spins, and trigger small avalanches. Radar observations during the hours of closest approach will be able to image the asteroid's surface with few-metre resolution, potentially revealing the changes. Shining like a 3rd magnitude star, Apophis will be plainly visible to the naked eye from rural areas and an easy (albeit fast-moving) target for small telescopes. No one in recorded history has ever seen an asteroid in space so bright. NASA, China, the Planetary Society and others are planning or contemplating missions to Apophis. The more we know about it the better. The next two flybys in 2029 and 2036 are safe, but analysts still haven't completely ruled out a low-probability impact in 2068.

ORIGIN OF ZODIACAL LIGHT
NASA

Look up to the night sky just before dawn, or after dusk, and you might see a faint column of light extending up from the horizon. That luminous glow is the zodiacal light, or sunlight reflected toward Earth by a cloud of tiny dust particles orbiting the Sun. Astronomers have long thought that the dust is brought into the inner solar system by a few of the asteroid and comet families that venture in from afar. But now, a team of Juno scientists argues that Mars may be the culprit. An instrument aboard the Juno spacecraft serendipitously detected dust particles slamming into the spacecraft during its journey from Earth to Jupiter. The impacts provided important clues to the origin and orbital evolution of the dust, resolving some mysterious variations of the zodiacal light. Onboard cameras snap photos of the sky every quarter of a second to determine Juno's orientation in space by recognizing star patterns in its images - an engineering task essential to the magnetometer's accuracy. But researchers hoped the cameras might also catch sight of an undiscovered asteroid. So one camera was programmed to report things that appeared in multiple consecutive images but weren't in the catalogue of known celestial objects. The camera showed that dust grains had smashed into Juno at about 16,000 kilometres per hour, chipping off submillimeter pieces of spacecraft. The spray of debris was coming from Juno's expansive solar panels - the biggest and most sensitive unintended dust detector ever built. Each piece of debris records the impact of an interplanetary dust particle, allowing astronomers to compile a distribution of dust along Juno's path. The majority of dust impacts were recorded between Earth and the asteroid belt, with gaps in the distribution related to the influence of Jupiter's gravity. According to the scientists, this was a radical revelation. Before now, scientists have been unable to measure the distribution of these dust particles in space. Dedicated dust detectors have had limited collection areas and thus limited sensitivity to a sparse population of dust. They mostly count the more abundant and much smaller dust particles from interstellar space. In comparison, Juno's expansive solar panels have 1,000 times more collection area than most dust detectors. Juno scientists determined that the dust cloud ends at Earth because Earth's gravity sucks up all the dust that gets near it. That's the dust we see as zodiacal light.

As for the outer edge, around 2 astronomical units (AU) from the Sun, it ends just beyond Mars. At that point, the scientists report, the influence of Jupiter's gravity acts as a barrier, preventing dust particles from crossing from the inner solar system into deep space. This same phenomenon, known as orbital resonance, also works the other way, where it blocks dust originating in deep space from passing into the inner solar system. The profound influence of the gravity barrier indicates that the dust particles are in a nearly circular orbit around the Sun, and the only object we know of in almost circular orbit around 2 AU is Mars, so the natural thought is that Mars is a source of this dust. The researchers developed a computer model to predict the light reflected by the dust cloud, dispersed by gravitational interaction with Jupiter that scatters the dust into a thicker disk. The scattering depends only on two quantities: the dust inclination to the ecliptic and its orbital eccentricity. When the researchers plugged in the orbital elements of Mars, the distribution accurately predicted the telltale signature of the variation of zodiacal light near the ecliptic. While there is good evidence now that Mars, the dustiest planet we know of, is the source of the zodiacal light, the team cannot yet explain how the dust could have escaped the grip of Martian gravity.

COMETS DELIVERED CARBON TO ROCKY PLANETS
University of Minnesota

In early 2016, an icy visitor from the edge of our solar system hurtled past Earth. It briefly became visible to stargazers as Comet Catalina before it slingshotted past the Sun to disappear forevermore out of the solar system. Among the many observatories that captured a view of this comet, which appeared near the Plough, was the Stratospheric Observatory for Infrared Astronomy (SOFIA), NASA's telescope on an airplane. Using one of its unique infrared instruments, SOFIA was able to pick out a familiar fingerprint within the dusty glow of the comet's tail -- carbon. Now this one-time visitor to our inner solar system is helping explain more about our own origins as it becomes apparent that comets like Catalina could have been an essential source of carbon on planets like Earth and Mars during the early formation of the solar system. Originating from the Oort Cloud at the farthest reaches of our solar system, Comet Catalina and others of its type have such long orbits that they arrive on our celestial doorstep relatively unaltered. This makes them effectively frozen in time, offering researchers rare opportunities to learn about the early solar system from which they come. SOFIA's infrared observations were able to capture the composition of the dust and gas as it evaporated off the comet, forming its tail. The observations showed that Comet Catalina is carbon-rich, suggesting that it formed in the outer regions of the primordial solar system, which held a reservoir of carbon that could have been important for seeding life.

While carbon is a key ingredient of life, early Earth and other terrestrial planets of the inner solar system were so hot during their formation that elements like carbon were lost or depleted. While the cooler gas giants like Jupiter and Neptune could support carbon in the outer solar system, Jupiter's jumbo size may have gravitationally blocked carbon from mixing back into the inner solar system. So how did the inner rocky planets evolve into the carbon-rich worlds that they are today? Researchers think that a slight change in Jupiter's orbit allowed small, early precursors of comets to mix carbon from the outer regions into the inner regions, where it was incorporated into planets like Earth and Mars. Comet Catalina's carbon-rich composition helps explain how planets that formed in the hot, carbon-poor regions of the early solar system evolved into planets with the life-supporting element. All terrestrial worlds are subject to impacts by comets and other small bodies, which carry carbon and other elements. We are getting closer to understanding exactly how these impacts on early planets may have catalysed life.

NEARBY EXOPLANET COULD CHANGE HOW WE LOOK FOR LIFE
University of New South Wales

A newly discovered planet could be our best chance yet of studying rocky planet atmospheres outside the solar system. The planet, called Gliese 486b (pronounced Glee-seh), is a 'super-Earth': that is, a rocky planet bigger than Earth but smaller than ice giants like Neptune and Uranus. It orbits a red dwarf star around 26 light-years away, making it a close neighbour -- galactically speaking. With a piping-hot surface temperature of 430 degrees Celsius, Gliese 486b is too hot to support human life. But studying its atmosphere could help us learn whether similar planets might be habitable for humans -- or if they're likely to hold other signs of life. Astronomers have known for a long time that rocky super-Earths must exist around the nearby stars, but haven't had the technology to search for them until recently. Like Earth, Gliese 486b is a rocky planet -- but that's where the similarities end. Our neighbour is 30 per cent bigger and almost three times heavier than Earth. It's possible that its surface -- which is hot enough to melt lead -- may even be scattered with glowing lava rivers. Super-Earths themselves aren't rare, but Gliese 486b special for two key reasons: firstly, its heat 'puffs up' the atmosphere, helping astronomers take atmospheric measurements; and secondly, it's a transiting planet, which means it crosses over its star from Earth's perspective -- making it possible for scientists to conduct in-depth analysis of its atmosphere. A planet's atmosphere can reveal a lot about its ability to support life. For example, a lack of atmosphere might suggest the planet's nearby star is volatile and prone to high stellar activity -- making it unlikely that life will have a chance to develop. On the other hand, a healthy, long-lived atmosphere could suggest conditions are stable enough to support life. Both options help astronomers solve a piece of the planetary formation puzzle.

Astronomers think Gliese 486b could have kept a part of its original atmosphere, despite being so close to its red dwarf star. As a transiting planet, Gliese 486b gives scientists two unique opportunities to study its atmosphere: first when the planet passes in front of its star and a fraction of starlight shines through its atmospheric layer (a technique called 'transmission spectroscopy'); and then when starlight illuminates the surface of the planet as it orbits around and behind the star (called 'emission spectroscopy'). In both cases, scientists use a spectrograph -- a tool that splits light according to its wavelengths -- to decode the chemical makeup of the atmosphere. This is the single best planet for studying emission spectroscopy of all the rocky planets we know. It's also the second-best planet to study transmission spectroscopy. Gliese 486b is a great catch for astronomers -- but you wouldn't want to live there. With a surface of 430 degrees Celsius, you wouldn't be able to go outside without some kind of spacesuit. The gravity is also 70 per cent stronger than on Earth, making it harder to walk and jump. Someone who weighed 50 kilograms on Earth would feel like they weighed 85 kilograms on Gliese 486b. Red dwarfs are the most common type of star, making up around 70 per cent of all stars in the universe. They are also much more likely to have rocky planets than Sun-like stars.

GIANT PLANET MAY BE ORBITING VEGA
University of Colorado at Boulder

Astronomers have discovered new hints of a giant, scorching-hot planet orbiting Vega, one of the brightest stars in the night sky. The work focuses on an iconic and relatively young star, Vega, which is part of the constellation Lyra and has a mass twice that of our own Sun. This celestial body sits just 25 light-years, or about 150 trillion miles, from Earth -- pretty close, astronomically speaking. Scientists can also see Vega with telescopes even when it's light out, which makes it a prime candidate for research. Despite the star's fame, researchers have yet to find a single planet in orbit around Vega. That might be about to change: Drawing on a decade of observations from the ground, astronomers unearthed a curious signal that could be the star's first-known world. If the team's findings bear out, the alien planet would orbit so close to Vega that its years would last less than two-and-a-half Earth days. (Mercury, in contrast, takes 88 days to circle the Sun). This candidate planet could also rank as the second hottest world known to science -- with surface temperatures averaging a searing 2,977 degrees Celsius. Scientists have discovered more than 4,000 exoplanets, or planets beyond Earth's solar system, to date. Few of those, however, circle stars that are as bright or as close to Earth as Vega. That means that, if there are planets around the star, scientists could get a really detailed look at them.

Vega is what scientists call an A-type star, the name for objects that tend to be bigger, younger and much faster-spinning than our own Sun. Vega, for example, rotates around its axis once every 16 hours -- much faster than the Sun with a rotational period of 27 Earth days. Such a lightning-fast pace can make it difficult for scientists to collect precise data on the star's motion and, by extension, any planets in orbit around it. The team pored through roughly 10 years of data on Vega collected by the Fred Lawrence Whipple Observatory in Arizona. In particular, the team was looking for a tell-tale signal of an alien planet -- a slight jiggle in the star's velocity. The team discovered a signal that indicates that Vega might host what astronomers call a "hot Neptune" or maybe a "hot Jupiter. That close to Vega, the candidate world might puff up like a balloon, and even iron would melt into gas in its atmosphere. The researchers have a lot more work to do before they can definitively say that they've discovered this sizzling planet. The easiest way to look for it might be to scan the stellar system directly to look for light emitted from the hot, bright planet.

ACCURATE TEMPERATURE OF RED SUPERGIANTS
University of Tokyo

Red supergiants are a class of star that end their lives in supernova explosions. Their lifecycles are not fully understood, partly due to difficulties in measuring their temperatures. For the first time, astronomers develop an accurate method to determine the surface temperatures of red supergiants. Stars come in a wide range of sizes, masses and compositions. Our Sun is considered a relatively small specimen, especially when compared to something like Betelgeuse which is known as a red supergiant. Red supergiants are stars over nine times the mass of our Sun, and all this mass means that when they die they do so with extreme ferocity in an enormous explosion known as a supernova, in particular what is known as a Type-II supernova. Type II supernovae seed the cosmos with elements essential for life; therefore, researchers are keen to know more about them. At present there is no way to accurately predict supernova explosions. One piece of this puzzle lies in understanding the nature of the red supergiants that precede supernovae. Despite the fact red supergiants are extremely bright and visible at great distances, it is difficult to ascertain important properties about them, including their temperatures. This is due to the complicated structures of their upper atmospheres which leads to inconsistencies of temperature measurements that might work with other kinds of stars.

In order to measure the temperature of red supergiants, astronomers needed to find a visible, or spectral, property that was not affected by their complex upper atmospheres. Chemical signatures known as absorption lines were the ideal candidates, but there was no single line that revealed the temperature alone. However, by looking at the ratio of two different but related lines -- those of iron -- we found the ratio itself related to temperature. And it did so in a consistent and predictable way. Researchers observed candidate stars with an instrument called WINERED which attaches to telescopes in order to measure spectral properties of distant objects. They measured the iron absorption lines and calculated the ratios to estimate the stars' respective temperatures. By combining these temperatures with accurate distance measurements obtained by the European Space Agency's Gaia space observatory, the researchers calculated the stars luminosity, or power, and found their results consistent with theory.

LARGEST SUPERNOVA REMNANT EVER DISCOVERED
Max-Planck-Gesellschaft

In the first all-sky survey by the eROSITA X-ray telescope onboard SRG, astronomers have identified a previously unknown supernova remnant, dubbed "Hoinga." The finding was confirmed in archival radio data and marks the first discovery of a joint Australian-eROSITA partnership established to explore our Galaxy using multiple wavelengths, from low-frequency radio waves to energetic X-rays. The Hoinga supernova remnant is very large and located far from the galactic plane -- a surprising first finding -- implying that the next years might bring many more discoveries. While the supernova itself is only observable on a timescale of months, their remnants can be detected for about 100,000 years. These remnants are composed of the material ejected by the exploding star at high velocities and forming shocks when hitting the surrounding interstellar medium. About 300 such supernova remnants are known today -- much less than the estimated 1200 that should be observable throughout our home Galaxy. So, either astrophysicists have misunderstood the supernova rate or a large majority has been overlooked so far. An international team of astronomers are now using the all-sky scans of the eROSITA X-ray telescope to look for previously unknown supernova remnants. With temperatures of millions of the degrees, the debris of such supernovae emits high-energy radiation, i.e. they should show up in the high-quality X-ray survey data.

After the astronomers found the object in the eROSITA all-sky data, they turned to other resources to confirm its nature. Hoinga is -- although barely -- visible also in data taken by the ROSAT X-ray telescope 30 years ago, but nobody noticed it before due to its faintness and its location at high galactic latitude. However, the real confirmation came from radio data, the spectral band where 90% of all known supernova remnants were found so far. The eROSITA X-ray telescope will perform a total of eight all-sky surveys and is about 25 times more sensitive than its predecessor ROSAT. Both observatories were designed, build and are operated by the Max Planck Institute for Extraterrestrial Physics. The astronomers expected to discover new supernova remnants in its X-ray data over the next few years, but they were surprised to identify one so early in the programme. Combined with the fact that the signal is already present in decades-old data, this implies that many supernova remnants might have been overlooked in the past due to low-surface brightness, being in unusual locations or because of other nearby emission from brighter sources. Together with upcoming radio surveys, the eROSITA X-ray survey shows great promise for finding many of the missing supernova remnants, helping to solve this long-standing astrophysical mystery.

MOVING SUPERMASSVE BLACK HOLE DETECTED
Harvard-Smithsonian Center for Astrophysics

Scientists have long theorized that supermassive black holes can wander through space -- but catching them in the act has proven difficult. For their search, the team initially surveyed 10 distant galaxies and the supermassive black holes at their cores. They specifically studied black holes that contained water within their accretion disks -- the spiral structures that spin inward towards the black hole. As the water orbits around the black hole, it produces a laser-like beam of radio light known as a maser. When studied with a combined network of radio antennas using a technique known as very long baseline interferometry (VLBI), masers can help measure a black hole's velocity very precisely. The technique helped the team determine that nine of the 10 supermassive black holes were at rest -- but one stood out and seemed to be in motion. Located 230 million light-years away from Earth, the black hole sits at the centre of a galaxy named J0437+2456. Its mass is about three million times that of our Sun. Using follow-up observations with the Arecibo and Gemini Observatories, the team has now confirmed their initial findings. The supermassive black hole is moving with a speed of about 110,000 miles per hour inside the galaxy J0437+2456. But what's causing the motion is not known. The team suspects there are two possibilities. But there's another, perhaps even more exciting possibility: the black hole may be part of a binary system. Further observations, however, will ultimately be needed to pin down the true cause of this supermassive black hole's unusual motion.

MOST DISTANT QUASAR WITH POWERFUL RADIO JETS DISCOVERED
ESO

Using the Very Large Telescope (VLT), astronomers have discovered and studied in detail the most distant source of radio emission known to date. The source is a "radio-loud" quasar -- a bright object with powerful jets emitting at radio wavelengths -- that is so far away its light has taken 13 billion years to reach us. We see it as it was when the Universe was just around 780 million years old. The discovery could provide important clues to help astronomers understand the early Universe. Quasars are very bright objects that lie at the centre of some galaxies and are powered by supermassive black holes. As the black hole consumes the surrounding gas, energy is released, allowing astronomers to spot them even when they are very far away. The newly discovered quasar is nicknamed P172+18. While more distant quasars have been discovered, this is the first time astronomers have been able to identify the tell-tale signatures of radio jets in a quasar this early on in the history of the Universe. Only about 10% of quasars -- which astronomers classify as "radio-loud" -- have jets, which shine brightly at radio frequencies. P172+18 is powered by a black hole about 300 million times more massive than our Sun that is consuming gas at a stunning rate. The astronomers think that there's a link between the rapid growth of supermassive black holes and the powerful radio jets spotted in quasars like P172+18. The jets are thought to be capable of disturbing the gas around the black hole, increasing the rate at which gas falls in. Therefore, studying radio-loud quasars can provide important insights into how black holes in the early Universe grew to their supermassive sizes so quickly after the Big Bang.

P172+18 was first recognised as a far-away quasar, after having been previously identified as a radio source, at the Magellan Telescope at Las Campanas Observatory in Chile. However, owing to a short observation time, the team did not have enough data to study the object in detail. A flurry of observations with other telescopes followed, including with the X-shooter instrument on ESO's VLT, which allowed them to dig deeper into the characteristics of this quasar, including determining key properties such as the mass of the black hole and how fast it's eating up matter from its surroundings. Other telescopes that contributed to the study include the National Radio Astronomy Observatory's Very Large Array and the Keck Telescope in the US.

NEW TYPE OF DARK ENERGY?
University of Southern Denmark

The Universe was created by the Big Bang 13.8 billion years ago, and then it started to expand. The expansion is ongoing: it is still being stretched out in all directions like a balloon being inflated. Physicists agree on this much, but something is wrong. Measuring the expansion rate of the Universe in different ways leads to different results. So, is something wrong with the methods of measurement? Or is something going on in the Universe that physicists have not yet discovered and therefore have not taken into account? Scientists propose the existence of a new type of dark energy in the Universe. If you include it in the various calculations of the expansion of the Universe, the results will be more alike. When physicists calculate the expansion rate of the Universe, they base the calculation on the assumption that the Universe is made up of dark energy, dark matter and ordinary matter. Until recently, all types of observations fitted in with such a model of the Universe's composition of matter and energy, but this is no longer the case. Conflicting results arise when looking at the latest data from measurements of supernovae and the cosmic microwave background radiation; the two methods quite simply lead to different results for the expansion rate. In the new model, physicists find that if there was a new type of extra dark energy in the early Universe, it would explain both the background radiation and the supernova measurements simultaneously and without contradiction. They believe that in the early Universe, dark energy existed in a different phase. You can compare it to when water is cooled and it undergoes a phase transition to ice with a lower density. In the same way, dark energy in this model undergoes a transition to a new phase with a lower energy density, thereby changing the effect of the dark energy on the expansion of the Universe. According to the calculations, the results add up if you imagine that dark energy thus underwent a phase transition triggered by the expansion of the Universe. Today we know approx. 20 per cent of the matter that the Universe is made of. It is the matter that you and I, planets and galaxies are made of. The Universe also consists of dark matter, which no one knows what is. In addition, there is dark energy in the Universe; it is the energy that causes the Universe to expand, and it makes up approx. 70 pct. of the energy density of the Universe.

GRAVITOMAGNETISM COULD DO AWAY WITH DARK MATTER
National Institute for Space Research

Observations of galactic rotation curves give one of the strongest lines of evidence pointing towards the existence of dark matter, a non-baryonic form of matter that makes up an estimated 85% of the matter in the observable Universe. Current assessments of galactic rotation curves are based upon a framework of Newtonian accounts of gravity. A new paper suggests that if this is substituted with a general relativity-based model, the need to recourse to dark matter is relieved, replaced by the effects of gravitomagnetism. The main role of dark matter has historically been to resolve the disparity between astrophysical observations and current theories of gravity. Put simply, if baryonic matter -- the form of matter we see around us every day which is made up of protons, neutrons and electrons -- is the only form of matter, then there shouldn't be enough gravitational force to prevent galaxies from flying apart. By disregarding general relativistic corrections to Newtonian gravity arising from mass currents, and by neglecting these mass currents, astronomers assert that these models also miss significant modifications to rotational curves -- the orbital speeds of visible stars and gas plotted against their radial distance from their galaxy's centre. This is because of an effect in general relativity not present in Newton's theory of gravity -- frame-dragging or the Lense Thirring effect. This effect arises when a massive rotating object like a star or black hole 'drags' the very fabric of spacetime along with it, in turn giving rise to a gravitomagnetic field. The paper presents a new model for the rotational curves of galaxies which is in agreement with previous efforts involving general relativity. The researcher demonstrates that even though the effects of gravitomagnetic fields are weak, factoring them into models alleviates the difference between theories of gravity and observed rotational curves -- eliminating the need for dark matter. The theory still needs some development before it is widely accepted, with the author particularly pointing out that the time evolution of galaxies modelled with this framework is a complex problem that will require much deeper analysis. The team concludes by suggesting that all calculations performed with thin galactic disk models performed up until this point may have to be recalculated, and the very concept of dark matter itself, questioned.

Bulletin compiled by Clive Down

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