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Topics - Geoffw

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Go to and make sure you have your say about the proposals for Carmarthenshire, Ceredigion and Pembrokeshire – before the 12th of July.

Gardening Groups / OLD HERBACEOUS at the Torch 4th july
« on: June 20, 2018, 07:30:10 PM »

WED 04 JUL 2018
£13.00 | £11.00 CONCESSION
Produced by Kick In The Head


Directed by Simon Downing

With Giles Shenton as Herbert Pinnegar

Described as “Downton Abbey with gardening tips”, Old Herbaceous is the humorous love story of a single-minded yet gentle man with a passion for plants and is a charming one man play which has entranced audiences around the country.

 An acute and sometimes hilarious observation of relationships between the classes in a simpler age, Old Herbaceous is sprinkled with witticisms and epithets. The evening blossoms into tender humour, much in the traditionally understated English style of the early 20th century.

"Wonderful production" - Surrey Advertiser
"Not to be missed" - BBC Radio Kent

As Old Herbaceous, renowned actor Giles Shenton truly lives the part of the legendary Head Gardener, Herbert Pinnegar, inviting you to feel included in a private chat from a bygone, comforting age.

 Keeping you engrossed, amused and emotionally engaged from start to finish, Old Herbaceous will leave you with a feeling that, perhaps, all’s right with the world.

Health and Well-being! / Refugee Week 2018
« on: June 18, 2018, 02:52:49 PM »

Astronomy Group / Saturn Observing Guide for 2018
« on: June 16, 2018, 10:14:51 AM »
More than a few beginners have looked at the planet Saturn through a small telescope and asked, “Is it real?” Oh, it's real.  And it's one of the most beautiful things you will ever see. The color of Saturn, the proportions, the apparent 3D perspective of this grand icy world make it arguably the finest sight accessible with a small telescope. The planet reaches opposition on June 27, 2018 and will remain bright and large in a telescope over the next few months.

Saturn, located above the “Teapot” of the constellation Sagittarius in the southeastern sky a few hours after sunset in late June 2018 as seen from the northern hemisphere. This view is visible nearly overhead for observers in the southern hemisphere (created with SkyX Serious Astronomer by Software Bisque)

Seeing The Rings Of Saturn
Saturn is one of the finest sights in a small telescope, even for beginners, and the planet reveals much to a patient observer.

There are the rings, of course, with their complex structure and segmentation. You’ll easily see the two main A and B rings, and in steady skies at 100x or more, you may see the large gap between the two main rings.  This is the Cassini division.

Can you discern the difference in brightness between the two rings?  Most observers agree the outer ‘A’ ring is fainter than the inner ‘B’ ring.  If you have rock-steady sky and a 12-inch or larger scope, look for the elusive Encke division, another gap near the outer edge of the A-ring.

More than most planets, Saturn displays a striking 3-D effect caused by the darkened edges of the disk and, when you can see them before and after opposition, the shadows cast by the rings on the planet. The apparent tilt of the rings this year is about 24o, nearly as large as it gets, and you may be able to trace the outer rings all the way around the planet, even the far side.

Also in the days around opposition, you may see the rings shine a little brighter than in the weeks before and after opposition. This is a consequence of the Seeliger effect, the temporary disappearance from our point of view of the shadows of the tiny ice particles that make up the rings.

The architecture of Saturn’s rings and cloud bands (image credit: Robert English).

The Moons Of Saturn
Like Jupiter, Saturn has a complex system of cloud bands visible with a small scope. But the planet is twice as far from the Sun as Jupiter so it doesn’t receive enough energy to drive as much active weather. The pale whitish-yellow bands on Saturn are by no means as obvious as Jupiter’s, but they are visible through most scopes. A yellow filter may help bring them out a little.

And there are the moons of Saturn.

The brightest is Titan, a moon which you can see with binoculars.  A 6-inch or larger scope may show the color of the dense yellow-orange clouds on this large 8th-magnitude moon, the second largest in the solar system.  The clouds hide the entire surface of Titan.  Which is too bad, because lakes of liquid hydrocarbons are spread across the rugged terrain of this planet-like world.

With a telescope of 4-inch aperture, and dark sky, you can also find the moons Iapetus, Rhea, Dione, and Tethys, all of which are approximately magnitude 10-11.  It’s hard to tell one from another.  To sort them out, try this online tool at Sky and Telescope. CLICK HERE

Saturn Observing Tips
Saturn delights most stargazers, but it can be frustrating to observe, especially this year when the planet is low on the horizon for northern observers. The visual image of the planet in a telescope is often small.  And if the atmosphere is not steady, the image tends to ripple and blur the delicate details in the clouds and the rings, so it’s never as clear as you see in professional images taken with big scopes.

Binoculars of 10-12x will show Saturn as a tiny, slightly non-circular disk, and they show Titan as a tiny point. But that’s about it. To clearly see the rings of Saturn, you will need a telescope.

Which telescope? Really, any telescope will give you a respectable view of the planet.  Refractors of longer focal length tend to give larger high-contrast images of planets.  Reflectors have a little less contrast because of the central obstruction of the secondary mirror. But if they are well collimated, reflectors do a fine job with planets.  Most of the best amateur planet imagers, for example, use SCT’s and Newtonians because these telescopes are available in higher apertures, and higher apertures enable higher resolution.

First, before you get started observing Saturn, make sure your telescope is aligned and cooled down to ambient temperature.  If you just take it from a warm house into the cool night air, there will be eddies of air in the telescope tube and movement of the mirror surface that will badly degrade the view until the temperature of the scope equilibriates with the rest of its surroundings.  It will take between 20 to 60 minutes for the scope to settle down, depending on the size of the mirror and lenses and so on.

Also, it helps to wait until Saturn is as high in the sky as possible before you observe. As mentioned, this year and for the next several apparitions, Saturn is south of the ecliptic and will never rise very high for northern-hemisphere observers. It is extremely well-placed for southern-hemisphere observers this year, however.

Don’t expect a Hubble-like image.  Despite its beauty, Saturn appears quite small in a telescope. The disk is only 18″ across at this opposition, about 1/3 the apparent size of Jupiter at its closest and about the same size as Mars at its opposition this year.  The rings extend farther, about 45-50”, which makes the planet appear larger but even with the rings it’s never larger than Jupiter at opposition.  You can never see Saturn through a telescope quite as well as you would like to.

Once you get the planet in view, pop a low-power eyepiece into your scope. At 25x, you’ll see Saturn as non-circular, and 50-60x should reveal the rings and the planet’s disk.

Saturn in a small telescope (credit:

Now move to at least 100x and take in the view.  The image will appear larger but a little fainter and possibly a little fuzzier. But keep moving to higher magnification until the image gets too fuzzy or faint.  The optimum magnification depends on your telescope and seeing conditions. In steady sky with a high-quality scope, you can get up to 50x to 60x your telescope aperture in inches, and if you can make it up to 300x or more in steady sky, you will get an excellent view.  But it’s not often you can use that much magnification. You need to experiment each night to determine the optimum magnification that will give you the best trade-off between image size, sharpness, and brightness. And yet if you’re patient, you can see a lot of detail on Saturn, even though it may be frustratingly small.  Even nights when the air isn’t so steady, wait for moments of good seeing when the image will suddenly sharpen and jump out at you like a tiny hologram. It’s darned impressive.

A colored filter, especially a #80A blue filter, can help you see fine detail near the poles and in the cloud bands of the planets.

From Earth, the view of Saturn and its rings changes slowly as the big planet revolves around the sun every 30 years.  Most of us, with a little luck, will get to see Saturn’s full range of faces just once or twice in our adult lives.  So don’t waste this opposition… head out when skies are clear to see the ringed planet for yourself.

U3A Walkers / Monday Walk: Leweston Farm to Cleddau Wen
« on: June 11, 2018, 10:29:27 PM »
Led by Nigel and Shirley Williams, nearly thirty U3A members set off in perfect weather for a stroll down through the fields and woodland of the Western Cleddau.  We walked about three and a half miles through mixed woodland, pasture and alongside the beautiful Western Claddau as it emerges from Treffgarne Gorge.  This was followed by a pleasant meal at Ye Olde Inn, Camrose.

Photography / Peak Design Camera Straps
« on: June 08, 2018, 07:00:46 PM »
I've been a big fan of Peak Design straps - especially with the anchors with the thin cord that fits through the lugs on cameras like my fujifilm X-T2.  Peak Design are now recommending against using these anchors as they have seen a small number of failures.  Not sure what to think as fitting the cords through the camera lugs was a major advantage to me of the straps

Astronomy Group / NEXT MEETING: Wednesday 27th June - Asteroids!
« on: June 08, 2018, 06:39:20 PM »
Asteroid: Doomsday or Payday?

DVD: Asteroid: Doomsday or Payday?
"The asteroid that exploded over Siberia—injuring more than 1,000 and damaging buildings in six cities—was a shocking reminder that Earth is a target in a cosmic shooting range. From the width of a football field to the size of a small city, these space rocks have the potential to be killers. In a collision with Earth, they could set off deadly blast waves, raging fires and colossal tidal waves. But some audacious entrepreneurs look up at asteroids and see payday, not doomsday. Some asteroids are loaded with billions of pounds' worth of elements like iron, nickel, and platinum. NASA is planning an ambitious mission to return samples from a potentially hazardous asteroid, and would-be asteroid miners are dreaming up their own program to scout for potentially profitable asteroids.

Will asteroids turn out to be our economic salvation—or instruments of extinction?"

Astronomy Group / Jupiter
« on: June 08, 2018, 06:29:45 PM »

The planet Jupiter is always one of the brightest objects in the night sky. It’s brighter than any star, and is only outshone by the planet Venus and the Moon, and, very rarely, by Mars and Mercury. Jupiter reaches a position for optimum viewing in a telescope once every 13 months, roughly, and it made its latest closest approach to Earth on May 9, 2018 when the planet appeared in the constellation Libra along the southern ecliptic. A couple of months before and after this date, Jupiter is in perfect position for viewing with a small telescope, or even a pair of binoculars. You can’t miss it: the planet is by far the brightest object in the southeastern sky. The visible face of Jupiter reveals so many interesting features in a small telescope that the planet is a favourite target for new and experienced stargazers.


Astronomy Group / The Night Sky This Month – June 2018
« on: June 05, 2018, 10:21:41 AM »
The Night Sky This Month – June 2018

Saturn at the 2014 opposition as imaged by Damian Peach (

The best stargazing of the year begins now. Through June and into July, the planets Jupiter, Saturn, and Mars make their best apparitions in many years and reveal plenty of fascinating detail in a small telescope. Venus and Mercury also make appearances, as does the big asteroid Vesta which grows bright enough to see without optics. And of course, the best part of the Milky Way returns with its rich collection of hundreds of star clusters, star-forming regions, dark nebulae, and star clouds. Here’s what to see in the night sky this month…

1 June. Look for Saturn about 1.5º south of the waning gibbous Moon well after midnight. The pair are just above the Teapot of Sagittarius in the southeastern sky.

3 June. The Moon is 3º north of the brightening planet Mars in southeastern pre-dawn sky.

6 June. Mercury lost in the Sun’s glare at superior conjunction on the far side of the Sun as seen from Earth. It will return to the evening sky later this month.

6 June. Last Quarter Moon, 18:32 UT

10 June. Venus is joined by the two brightest stars of Gemini, Castor and Pollux, in the western sky after sunset. The planet is about 28 degrees above the horizon in early June for northern observers, and slightly higher for southern observers. It brightens a little to magnitude -4.1 over the month and slowly begins to grow larger (about 15”) and less illuminated (from 80% to 70%).

Venus, Castor, and Pollux in the western sky after sunset on June 10, 2018.

13 June. New Moon, 19:43 UT

15 June. Mercury emerges in the evening sky for the rest of June and into July. Look for the planet getting higher in the western sky after sunset. By month’s end, it sets more than an hour after the Sun and shines at an impressive magnitude 0.1. A pair of binoculars will help you pick it out of the twilight glare. The planet is about 6” across and, in a telescope, reveals a gibbous disk about 60% illuminated.

Mercury and Venus in the western sky after sunset in late June 2018.

16 June. Spectacular Venus is just 2º north of the slender crescent Moon (about two finger widths held at arm’s length). The Moon is also about 1.5º south of M44, the Beehive star cluster. They all make for fine viewing through a pair of binoculars in the western sky after the Sun goes down. I challenge you to find a prettier sight anywhere.

19 June. The asteroid Vesta reaches opposition. After the dwarf planet Ceres, Vesta is the second-most massive body in the solar system asteroid belt. Its mean diameter is a respectable 525 km. But, unlike Ceres, it does not have sufficient gravity to pull itself into a spherical shape, which is why it didn’t make the grade as a dwarf planet. Vesta lies in northern Sagittarius, not far from Saturn, and reaches a peak brightness of magnitude 5.3. That’s bright enough to see without optical aid in dark sky. The chart below, courtesy of Sky and Telescope magazine, shows you where to find it from day to day.

A chart showing the position of Vesta (and Saturn) through June and July. Credit: Sky and Telescope.

20 June. Grab your binoculars and have a look at Venus just 0.4º north of the Beehive cluster in the western sky after sunset.

20 June. First Quarter Moon, 10:51 UT

21 June. At 10:07 UT, the Sun reaches northern solstice, the northernmost point on the ecliptic, where it appears to stand still for a day before slowly moving southward again. This marks the first day of summer in the northern hemisphere and the first day of winter south of the equator. At solstice, the Sun lies near the star Propus at the foot of Gemini, not far from the star cluster M35.

23 June. Jupiter lies just 4º south of the waxing gibbous Moon. Just a month past opposition, the big planet remains a resplendent sight in June. It slowly dims and grows smaller this month, but at magnitude -2.4, it’s still brighter by far than any star. The planet’s disk spans about 45”and continues to reveal plenty of detail in a telescope. Learn more about what to see on and around Jupiter in the Cosmic Pursuits Jupiter observing guide.

27 June. The planet Saturn reaches opposition, rising in the eastern sky as the Sun sets in the west. This marks the closest approach of Earth to the ringed planet in 2018. The planet reaches magnitude 0.0 and its disk spans about 18”. The rings are more than twice as wide as the disk. This year, the rings are tilted splendidly towards our line of sight by some 24º. It’s a great time to see this planet, which many new and experienced skywatchers rank as the most beautiful thing you can see through a telescope. Because the planet is in the southern reaches of the ecliptic, this year’s apparition favors southern stargazers. But northerners can see plenty on nights of good seeing.

The location of Jupiter and Saturn in the late part of June 2018.

28 June. Mars stops its eastward motion and becomes stationary relative to the background stars. For the next many weeks, and through its opposition on July 27, the planet will appear to move westward from day to day. This is called retrograde motion. At the end of June, Mars lies well to the east of Saturn in the constellation Capricorn. The planet gets down to business this month, brightening from magnitude -1.2 to -2.2 and growing to 20” across. On nights of steady seeing, it will reveal plenty of detail in a good telescope at moderate to high magnification. The planet rises around midnight as June begins and 10:30 p.m. as the month ends.

28 June. Full Moon, 04:53 UT

THE SOCIETY FOR POPULAR ASTRONOMY Electronic News Bulletin No. 470 2018 June 3
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


A new study has discovered the first known permanent immigrant to our Solar
System. The asteroid, currently nestling in Jupiter's orbit, is the first
asteroid known to have been captured from another star system. An object
known as 'Oumuamua was the last interstellar interloper to hit the headlines,
in 2017. However, it was just a tourist passing through, whereas the new
exo-asteroid -- given the catchy name (514107) 2015 BZ509 -- is a long-term
resident. All of the planets in the Solar System, and the vast majority of
other objects as well, travel around the Sun in the same direction. But
2015 BZ509 is different -- it moves in the opposite direction, in what is
known as a 'retrograde' orbit. How the asteroid came to move in that way
while sharing Jupiter's orbit has until now been unknown. If 2015 BZ509
were a native of our system, it should have had the same original direction
as all of the other planets and asteroids, inherited from the cloud of gas
and dust that formed them. However, the team ran simulations to trace the
location of 2015 BZ509 right back to the birth of our Solar System, 4.5
billion years ago when the era of planet formation ended. They show that
2015 BZ509 has always moved in that way, and so could not have been there
originally and must have been captured from another system.

Asteroid immigration from other star systems occurs because the Sun
initially formed in a tightly-packed star cluster, where every star had
its own system of planets and asteroids. The close proximity of the stars,
aided by the gravitational forces of the planets, helped those systems
attract, remove and capture asteroids from one another. The discovery of
the first permanent asteroid immigrant in the Solar System has important
implications for the open problems of planet formation, Solar-System
evolution, and possibly the origin of life itself. Understanding exactly
when and how 2015 BZ509 settled in the Solar System may provide clues about
the Sun's original star nursery, and about the potential enrichment of our
early environment with components necessary for the appearance of life on


Engineers working with NASA's 'Curiosity' Mars rover have been hard at work
testing a new way for the rover to drill rocks and extract powder from them.
That effort has produced the first drilled sample on Mars in more than a
year. Curiosity tested percussive drilling, penetrating about 50 mm into a
rock called 'Duluth'. NASA has been testing that drilling technique since
a mechanical problem took Curiosity's drill offline in 2016 December. The
technique, called 'Feed Extended Drilling', keeps the drill's bit extended
out past two stabilizer posts whose original purpose was to steady the drill
against Martian rocks. It lets Curiosity drill using the force of its
robotic arm, a little more like the way a human would drill into a wall at
home. Drilling is a vitally important part of Curiosity's capabilities to
study Mars. Inside the rover are two laboratories that are able to conduct
chemical and mineralogical analyses of rock and soil samples. The samples
are acquired from Gale Crater, which the rover has been exploring since

Southwest Research Institute

Scientists have developed what they call 'the giant comet' cosmochemical
model of Pluto's formation. At the heart of the research is the nitrogen-
rich ice in Sputnik Planitia, a large glacier that forms the left lobe of
the bright Tombaugh Regio feature on Pluto's surface. Researchers found an
intriguing consistency between the estimated amount of nitrogen inside the
glacier and the amount that would be expected if Pluto were formed by the
agglomeration of roughly a billion comets or other Kuiper-Belt objects
similar in chemical composition to 67P, the comet explored by Rosetta. In
addition to the comet model, scientists also investigated a solar model,
with Pluto forming from very cold ices that would have had a chemical
composition that more closely matches that of the Sun. Scientists needed to
understand not only the nitrogen present in Pluto now -- in its atmosphere
and in glaciers -- but also how much of that volatile element potentially
could have leaked out of the atmosphere and into space over the aeons.
They then needed to reconcile the proportion of carbon monoxide to nitrogen
to get a more complete picture. Ultimately, the low abundance of carbon
monoxide in Pluto points to burial in surface ices or to destruction from
liquid water. The research suggests that Pluto's initial chemical makeup,
inherited from cometary building blocks, was chemically modified by liquid
water, perhaps even in a sub-surface ocean. However, the solar model also
satisfies some constraints. While the research pointed to some interesting
possibilities, many questions remain to be answered. The research builds
upon the success of the New Horizons and Rosetta missions to expand our
understanding of the origin and evolution of Pluto. Using chemistry as a
detective's tool, scientists were able to trace certain features we see on
Pluto today to formation processes from long ago. That leads to a new
appreciation of the richness of Pluto's 'life story', which we are only
now starting to grasp.


The Kepler planet-hunting spacecraft began the 18th observing campaign of
its extended mission, K2, on May 12. For the next 82 days, Kepler will
stare at clusters of stars, faraway galaxies, and a handful of Solar-System
objects, including comets, objects beyond Neptune, and an asteroid. The
Kepler spacecraft is expected to run out of fuel within several months.
Campaign 18 is a familiar patch of space, as it is approximately the same
region of sky that Kepler observed during Campaign 5 in 2015. One of the
advantages of observing a field again is that planets outside the Solar
System, called exoplanets, may be found orbiting farther from their stars.
Astronomers hope not only to discover new exoplanets during this campaign,
but also to confirm candidates that were previously identified.
Open star clusters are regions where many stars formed at roughly the same
time; they include Messier 67 and Messier 44, the latter also known as
Praesepe or the Beehive cluster. Home to six known exoplanets, Praesepe
will be searched anew for objects that are transiting, or crossing, around
the same or other stars. At approximately 800 million years old, the stars
in Praesepe are young in comparison with the Sun. Many of those youthful
stars are active and have large spots that can reveal information about the
star's magnetic field, a fundamental component of a star that drives flaring
and other activity. By comparing brightness data collected in Campaigns 18
and 5, scientists hope to learn more about how a star's spots cycle over
At several billion years, the Messier 67 cluster is much older and has many
Sun-like stars. It is one of the best-studied open clusters in the sky.
[The moderator of these Bulletins was among the authors in the 1980s of
papers that gave radial velocities for no fewer than 170 stars in the M67
field and spectroscopic orbits for 22 of them.] Astronomers will continue
their studies of stellar astrophysics by analyzing M67's stars for changes
in brightness. They will search for the signatures of exoplanets, observe
the pulsations of evolved stars, and measure the rotation rates of many
other stars in the cluster. Beyond the star clusters, Kepler will observe
blazars, the energetic nuclei of faraway galaxies with black holes in their
centres. Those objects propel jets of hot plasma towards the Earth (though
they are far too distant to affect us). The most notable of the targets is
OJ 287, a system hosting two black holes in orbit around each other, one of
which is 18 billion times the mass of the Sun! Even closer to home,
Kepler will look at Solar-System objects, including comets, trans-Neptunian
objects, and the near-Earth asteroid 99942 Apophis. That 1,000-foot chunk
of rock will pass within 20,000 miles of the Earth in the year 2029 -- close
astronomically but still far enough away not to pose any danger to the Earth.

Case Western Reserve University

Astronomers have been observing M51, the Whirlpool Galaxy, since the 1800s;
its signature spiral structure informed the earliest debates over the nature
of galaxies and the cosmos at large. But no one -- not with the naked eye
or with increasingly powerful modern telescopes -- had ever seen what
astronomers first observed with a refurbished 75-year-old telescope in the
mountains of southwest Arizona. What it was turned out to be a massive
cloud of ionized hydrogen gas spewed from a nearby galaxy and then
essentially 'cooked' by radiation from the galaxy's central black hole.
The discovery of the giant gas cloud, first observed in 2015, potentially
provides astronomers with an unexpected 'front-row seat' to view the
behaviour of a black hole and the associated galaxy as it consumes and
'recycles' hydrogen gas. We know of a few clouds like it in distant
galaxies, but not in one so 'close' to us. It gives astronomers a great
opportunity to study up 'close' how gas is ejected from galaxies and how
black holes can influence large regions of space around those galaxies.
The astronomers used the Burrell Schmidt telescope of the Warner & Swasey
Observatory, now at Kitt Peak. Although older and smaller than most
telescopes on Kitt Peak, the telescope is constructed in such a way as to
provide a wide field of view, while also keeping out unwanted stray light.
That allows astronomers to see things that other telescopes don't: diffuse
patches of light that are "over 100 times fainter than the blackest night
sky you can imagine". What the telescope really does well is measure very
diffuse, low-surface-brightness light emitted by gas or stars around a
Researchers had originally been imaging the Whirlpool to map the faint
streamers of starlight torn off by the collision between the galaxies.
Thinking that there might also be gas in those streamers, the team fitted
the telescope with a special filter to see hot, ionized hydrogen gas,
which emits a specific wavelength of light. Finding stars is relatively
straightforward, but gas does not shine at all wavelengths. That is one
of several reasons why no one had ever seen that before -- earlier studies
using such hydrogen filters to look for ionized gas could not detect
emission so faint and over such a wide area around the Whirlpool. But
there was still one thing to double-check: the team worried that they were
actually seeing a diffuse cloud of gas right in front of us in our own
galaxy and it wasn't really part of M51. The astronomers called on the
nearby WIYN Observatory to confirm the cloud's association with M51. The
WIYN 3.5-m telescope was equipped with an instrument capable of taking a
detailed spectrum of the cloud to measure its velocity. Once the WIYN
people had taken the spectrum of the cloud, they were able to tell how fast
it was moving away from us, and it became immediately apparent that it was
part of M51, not something nearer to us. The discovery's role in under-
standing nmore clearly how galaxies eject and 'recycle' their gas and
stars will be determined in the coming years as more researchers dig into
information that had been there all along -- even if unseen until now.


Astronomers have used observations from the Atacama Large Millimeter/sub-
millimeter Array (ALMA) and the Very Large Telescope (VLT) to determine
that star formation in the very distant galaxy MACS 1149-JD1 started at
an unexpectedly early stage, 'only' 250 million years after the Big Bang.
That discovery also represents the most distant oxygen ever detected in
the Universe and the most distant galaxy ever observed by ALMA or the VLT.
The team detected a very faint glow emitted by ionized oxygen in the
galaxy. As that infrared light travelled across space, the expansion of the
Universe stretched it to wavelengths more than ten times longer by the time
it reached the Earth and was detected by ALMA. The team inferred that the
signal was emitted 13.3 billion years ago (or 500 million years after the
Big Bang), making it the most distant oxygen ever detected. The presence
of oxygen is a clear sign that there must have been even earlier generations
of stars in that galaxy. In addition to the glow from oxygen picked up by
ALMA, a weaker signal of hydrogen emission was also detected by ESO's Very
Large Telescope (VLT). The distance to the galaxy determined from that
observation is consistent with the distance from the oxygen observation.
That makes MACS 1149-JD1 the most distant galaxy with a precise distance
measurement and the most distant galaxy ever observed with ALMA or the VLT.
For a period after the Big Bang there was no oxygen in the Universe; it was
created by the fusion processes of the first stars and then released when
those stars died. The detection of oxygen in MACS 1149-JD1 indicates that
those earlier generations of stars had already been formed and expelled
oxygen by just 500 million years after the beginning of the Universe.
But when did that earlier star formation occur? To find out, the team
reconstructed the earlier history of MACS 1149-JD1 using infrared data taken
with the Hubble and Spitzer space telescopes. They found that the observed
brightness of the galaxy is well explained by a model where the onset of
star formation corresponds to 'only' 250 million years after the Universe
began. The maturity of the stars seen in MACS 1149-JD1 raises the question
of when the very first galaxies emerged from total darkness, an epoch
astronomers romantically term 'cosmic dawn'. By establishing the age of
MACS 1149-JD1, the team has effectively demonstrated that galaxies existed
earlier than those that we can currently detect directly.
Bulletin compiled by Clive Down (c) 2018 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 £22 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 web site:[/b]]

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