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Astronomy Group / A New Planet in the Neighbourhood
« on: November 18, 2018, 11:20:20 AM »

A New Planet in the Neighbourhood

It was a discovery nearly a century in the making, but astronomers have finally detected a planet around Barnard’s Star, the nearest single star to Earth. Known as the "white whale" of exoplanet hunters, Barnard's Star has long tantalized and frustrated astronomers with false results of planetary detection, and it inspired a generation of science fiction writers to imagine what kind of worlds lie in its feeble gravitational embrace. The newly discovered planet isn't exactly an Earth-like, but it is the second-nearest exoplanet to our solar system and it's probably twice the age of our own solar system. Here are the details...


2
 
THE SOCIETY FOR POPULAR ASTRONOMY Electronic News Bulletin No. 480 2018 November 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/
 
COMET TAILS BLOWING IN SOLAR WIND
NASA/Goddard Space Flight Center

In 2007 January, scientists saw the first data from the STEREO (Solar and
Terrestrial Relations Observatory) spacecraft. Instead of the star field
they expected, a pearly white, feathery smear filled the frame. That bright
object was not a defect: it was the first satellite image of Comet McNaught
C/2006 P1), named for astronomer Robert McNaught, who discovered it in 2006
August. It was one of the brightest comets of the past 50 years. Through-
out 2007 January, the comet fanned across the Southern Hemisphere's sky, so
bright that it was visible to the naked eye even during the day. McNaught
belongs to a rare group of comets, dubbed the Great Comets and known for
their exceptional brightness. Setting McNaught apart further still from
its peers, however, was its highly structured tail, composed of many
distinct dust bands, called striae or striations, that stretched more than
100 million miles behind the nucleus. One month later, a spacecraft called
Ulysses encountered the comet's long tail. McNaught was a huge deal when it
came, because it was so ridiculously bright and beautiful in the sky. It
had striae -- dusty fingers that extended across a great expanse of the sky.
It was one of the most beautiful comets seen for decades.
How exactly the tail broke up, scientists do not know. It called to mind
reports of another storied comet from long ago -- the Great Comet of 1744,
which was said to have fanned out dramatically in six tails over the
horizon, a phenomenon that astronomers then could not explain. By
untangling the mystery of McNaught's tail, scientists hoped to learn
something new about the nature of comets -- and solve two cosmic mysteries
in one. A key difference between studying comets in 1744 and 2007 is, of
course, our ability now to do so from space. In addition to STEREO's
serendipitous sighting, another mission, SOHO -- the Solar and Heliospheric
Observatory -- made regular observations as McNaught flew by the Sun.
Researchers hoped that those images might contain their answers.
Comets are cosmic crumbs of frozen gas, rock and dust left over from the
formation of the Solar System 4.6 billion years ago -- so they may contain
important clues about Solar System's early history. Those clues may be
unlocked, as if from a time capsule, every time a comet's orbit brings it
close to the Sun. Intense heat vaporizes the frozen gases and releases the
dust within, which streams behind the comet, forming two distinct tails: an
ion tail carried by the solar wind -- the constant flow of charged particles
from the Sun -- and a dust tail. Understanding how dust behaves in the tail
-- how it fragments and clumps together -- can teach scientists a great deal
about similar processes that formed dust into asteroids, moons and even
planets all those billions of years ago. Appearing as one of the biggest
and most structurally complex comets in recent history, McNaught was a
particularly good subject for that type of study. Its brightness and high
dust production made it much easier to resolve the evolution of fine
structures in its dust tail. Astronomers noticed weird goings-on in the
images of those striations, a disruption in the otherwise clean lines. The
rift seemed to be located at the heliospheric current sheet, a boundary
where the magnetic orientation, or polarity, of the electrified solar wind
changes direction. That puzzled scientists, because while they have long
known that a comet's ion tail is affected by the solar wind, they had never
seen the solar wind affect dust tails before. Dust in McNaught's tail --
roughly the size of cigarette smoke -- is too heavy, the scientists thought,
for the solar wind to push it around. On the other hand, an ion tail's
miniscule, electrically charged ions and electrons easily sail along the
solar wind. But it was difficult to tell exactly what was going on with
McNaught's dust, and where, because at roughly 60 miles per second, the
comet was rapidly travelling in and out of STEREO and SOHO's view. In
looking for a way to bring it all together to get a complete picture of
what's happening in the tail they used an image-processing technique that
compiles all the data from different spacecraft using a simulation of the
tail, where the location of each tiny speck of dust is mapped by solar
conditions and physical characteristics like its size and age, or how long
it had been since it had flown off the head, or coma, of the comet. The end
result is a map, which layers information from all the images taken at any
given moment, allowing the dust's movements to be followed. The maps made
it easier to explain the strange effect that drew attention to the data in
the first place. Indeed, the current sheet was the culprit behind the
disruptions in the dust tail, breaking up each striation's smooth, distinct
lines. For the two days it took the full length of the comet to traverse
the current sheet, whenever dust encountered the changing magnetic condi-
tions there, it was jolted out of position, as if crossing some cosmic speed
bump. That is strong evidence that the dust is electrically charged, and
that the solar wind is affecting the motion of that dust. Scientists have
long known that the solar wind affects charged dust; missions like Galileo,
Cassini and Ulysses watched it move electrically-charged dust through the
space near Jupiter and Saturn. But it was a surprise for them to see the
solar wind affect larger dust grains like those in McNaught's tail -- about
100 times bigger than the dust seen ejected from around Jupiter and Saturn
-- because they are that much heavier for the solar wind to push. The work
sheds light on the nature of striated comet tails from the past and provides
a lens for studying other comets in the future. But it also opens a new
line of questioning: what roles did the Sun have in the Solar System's
formation and early history?

AMATEUR ASTRONOMERS FIND A BRIGHT NEW COMET
Spaceweather.com

There's a new comet in the morning sky. Discovered just last week by three
amateur astronomers -- one in Arizona and two in Japan -- Comet Machholz-
Fujikawa-Iwamoto (C/2018 V1) has quadrupled in brightness over the past few
days and is now glowing like a fuzzy 8th-magnitude star in the constellation
Virgo. The discovery of a comet by amateur astronomers is a rare event
nowadays because robotic Near-Earth-Object search programmes usually catch
them first. Comet Machholz-Fujikawa-Iwamoto appears to be a first-time
visitor to the inner Solar System. It is plunging toward the Sun on a
nearly-parabolic orbit that will take it just inside the orbit of Mercury.
Closest approach to the Sun (0.38 AU) is on Dec. 3-4; closest approach to
Earth (0.67 AU) is Nov. 27. Fresh comets like this one are notoriously
unpredictable. They can surge in brightness, seeming to promise a
spectacular display, but suddenly fizzle out as their deposits of ice are
exhausted by solar heat. So it is uncertain whether the new comet will even
become a naked-eye object. At the moment it is an easy target for amateur
telescopes.

AGEING FLOCK OF STARS IN WILD DUCK CLUSTER
University of Arizona

Astronomers have long believed that many open clusters consist of a single
generation of stars because, once stars have formed, their radiation blows
away nearby material needed to make new stars. But in M11 (the 'Wild Duck
Cluster') -- stars of the same brightness appear in different colours,
suggesting that they are of different ages. Unless scientists had missed
important clues about stellar evolution, there had to be another explanation
for the spread of colours in that cluster of about 2,900 stars. Open
clusters contain thousands of stars that astronomers hypothesize formed
from the same giant clouds of gas. Those stars come in all sizes, from
short-lived, giant blue stars dozens of times more massive than our Sun, to
long-lived low-mass dwarfs that will burn for 10 billion years or longer.
The brightness and colour of each star change as it grows older, allowing
scientists to determine its age. Astronomers plot stars' brightness and
colour in a diagonal line called the main sequence in the Herttzsprung--
Russell Diagram. The turning point -- the point at which a star ages and
veers off the main sequence -- is used to estimate the ages of clusters on
the basis of the known life expectancy of each star. If the stars leave the
main sequence at the same point, then they must all be the same age. In
M11, however, the stars veer off the diagonal at different points. The team
observed M11 with the MMT to examine the colour spectrum of the stars. They
used the 'Hectochelle', which can capture detailed spectra of many stars at
once.
Rotation of a star causes its spectral lines to be broadened. The spectra
of stars in M11 show that they are spinning at different rates. A rapidly
rotating star can remain in the main-sequence stage longer than a slowly
rotating one. A wide range of rotational velocities of stars in a cluster
results in differences of lifetimes among the stars. Rotational speed is
like a fountain of youth to a star: the faster it spins, the better it mixes
hydrogen -- the star's fuel -- into its core. The more hydrogen the core
receives, the longer the star lives, causing it to appear redder than
younger siblings. Stars in the cluster appear of different colours because
the cloud in which they were born set them in motions that would extend the
lifetimes of some of them.

ULTRA-HOT GAS AROUND WHITE DWARFS
RAS

Solving a decades-old mystery, astronomers have discovered an extremely hot
magnetosphere around a white dwarf, a remnant of a star like our Sun. White
dwarfs are the final stage in the lives of stars like our Sun. At the end
of their lives, those stars eject their outer atmospheres, leaving behind a
hot, compact and dense core that cools over billions of years. The
temperature on their surfaces is typically around 100,000 degrees C. Some
white dwarfs, though, challenge scientists, as they show evidence for highly
ionized metals. In astronomy, 'metals' means every element heavier than
helium, and high ionization here means that all but one of the outer
electrons usually in their atoms have been stripped away. That process
needs a temperature of 1 million degrees C, far hotter than the surfaces of
even the hottest white-dwarf stars. The team used the 3.5-m Calar Alto
telescope in Spain to discover and observe a white dwarf in the direction of
the constellation of Triangulum, catalogued as GALEXJ014636.8+323615,
located 1200 light-years away. Spectra of the white dwarf revealed the
signatures of highly-ionized metals. Intriguingly, they varied over a
period of six hours -- the same time it takes for the white dwarf to rotate.
The team concluded that the magnetic field around the star -- the magneto-
sphere -- traps material flowing from its surface. Shocks within the
magnetosphere heat the material dramatically, stripping almost all the
electrons from the metal atoms. The axis of the magnetic field of the white
dwarf is tilted with respect to the rotational axis. That means that the
amount of shock-heated material we see varies as the star rotates. More and
more such stars have been found, without there being any clue as to where
the highly-ionized metals come from, but now the shock-heated magnetosphere
model finally explains their origin. Magnetospheres are found around other
types of stars, but this is the first report of one around a white dwarf.
The discovery might have far-reaching consequences. Ignoring their
magnetospheres could mean measurements of other basic properties of white
dwarfs are wrong, such as their temperatures and masses. The team now plans
to model them in detail and to extend the research by studying more of them.

MATERIAL ORBITING CLOSE TO BLACK HOLE
ESO

ESO's GRAVITY instrument has added further evidence to the long-standing
assumption that a supermassive black hole lurks in the centre of the Milky
Way. New observations show clumps of gas swirling around at about 30% of
the speed of light on a circular orbit just outside its event horizon -- the
first time material has been observed orbiting close to the point of no
return, and the most detailed observations yet of material orbiting so close
to a black hole. The GRAVITY instrument on the Very Large Telescope (VLT)
Interferometer has been used by scientists to observe flares of infrared
radiation coming from the accretion disc around Sagittarius A*, the massive
object at the heart of the Milky Way. The observed flares provide long-
awaited confirmation that the object in the centre of our galaxy is, as has
long been assumed, a supermassive black hole. The flares originate from
material orbiting very close to the black hole's event horizon, making these
observations the most detailed ones yet of material orbiting so close to a
black hole. While some matter in the accretion disc -- the belt of gas
orbiting Sagittarius A* at relativistic speeds -- can orbit the black hole
safely, anything that gets too close is doomed to be pulled beyond the event
horizon. The closest point to a black hole that material can orbit without
being irresistibly drawn inwards by the immense mass is known as the
innermost stable orbit, and it is from there that the observed flares
originate. Those measurements were only possible thanks to international
collaboration and state-of-the-art instrumentation. The GRAVITY instrument
which made this work possible combines the light from four telescopes of
the VLT to create a virtual super-telescope 130 metres in diameter, and
has already been used to probe the nature of Sagittarius A*.
Earlier this year, GRAVITY and SINFONI, another instrument on the VLT,
allowed the same team accurately to measure the close fly-by of the star S2
as it passed through the extreme gravitational field near Sagittarius A*,
and for the first time revealed the effects predicted by Einstein's general
relativity in such an extreme environment. During S2's close fly-by, strong
infrared emission was also observed. That emission, from highly energetic
electrons very close to the black hole, was visible as three prominent
bright flares, and exactly matches theoretical predictions for hot spots
orbiting close to a black hole of four million solar masses. The flares are
thought to originate from magnetic interactions in the very hot gas orbiting
very close to Sagittarius A*.

ELUSIVE STAR HAS ORIGINS CLOSE TO BIG BANG
Johns Hopkins University

Astronomers have found what could be one of the Universe's oldest stars, a
body almost entirely made of materials spewed from the Big Bang. The
discovery of this approximately 13.5-billion-year-old tiny star means that
more stars with very low mass and very low metal content are likely to be
out there -- perhaps even some of the Universe's very first stars. The star
is unusual because unlike other stars with very low metal content, it is
part of the Milky Way's 'thin disc' -- the part of the Galaxy in which our
own Sun resides. And because this star is so old, researchers say it is
possible that our galactic neighbourhood is at least 3 billion years older
than previously thought. The Universe's first stars would have consisted
entirely of elements like hydrogen, helium, and small amounts of lithium.
Those stars then produced elements heavier than helium in their cores and
seeded the Universe with them when they exploded as supernovae. The next
generation of stars formed from clouds of material laced with those metals,
incorporating them into their makeup. The metal content, or metallicity,
of stars in the Universe increased as the cycle of star birth and death
continued. The newly discovered star's extremely low metallicity indicates
that, in a cosmic family tree, it could be as little as one generation
removed from the Big Bang. Indeed, it is the new record holder for the star
with the smallest complement of heavy elements -- it has about the same
heavy-element content as the planet Mercury. In contrast, our Sun is many
generations down the line and has a mass of heavy elements equal to 14
Jupiters. Astronomers have found around 30 ancient 'ultra-metal-poor'
stars with the approximate mass of the Sun. The star the team found,
however, is only 14 percent the mass of the Sun.
The star is part of a two-star system orbiting around a common point. The
team found the tiny, almost invisibly faint, secondary star after another
group of astronomers discovered the much brighter primary star. That team
measured the primary's composition by studying a high-resolution optical
spectrum, and found it to have extremely low metallicity. The existence of
the companion star turned out to be the big discovery. The team was able to
infer its mass by studying the slight variation that it induces in the
radial velocity of the primary star. As recently as the late 1990s,
researchers believed that only massive stars could have formed in the
earliest stages of the Universe -- and that they could never be observed
because they burn through their fuel and die so quickly. But as astro-
nomical simulations became more sophisticated, they began to hint that, in
certain situations, a star from that time period but with particularly low
mass could still exist. Unlike huge stars, low-mass ones can live for
exceedingly long times. Red dwarf stars, for instance, with a fraction of
the mass of the Sun, are thought to live for billions of years. The
discovery of the new ultra-metal-poor star, named 2MASS J18082002-5104378 B, opens the possibility of observing even older stars.

MILKY WAY MERGED WITH LARGE GALAXY
University of Groningen

Some ten billion years ago, the Milky Way merged with a large galaxy. The
stars from that partner, named Gaia-Enceladus, make up most of the Milky
Way's halo and also shaped its thick disc, giving it its inflated form.
Large galaxies like our Milky Way are the result of mergers of smaller
galaxies. An outstanding question is whether a galaxy like the Milky Way is
the product of many small mergers or of a few large ones. Researchers have
looked for 'fossils' in our Milky Way which might offer some hints as to its
evolution. The research uses the chemical composition, the position and the
trajectory of stars in the halo to deduce their history and thereby to
identify the mergers which created the early Milky Way. The second data
release from the Gaia satellite mission last April provided data on around
1.7 billion stars, and they has been used to look for traces of mergers in
the halo. Astronomers expected stars from fused satellites in the halo.
What they did not expect to find was that most halo stars actually have a
shared origin in one very large merger. The chemical signature of many halo
stars was clearly different from that of the 'native' Milky Way stars. They
are a fairly homogeneous group, which indicates that they share a common
origin. In plots of both trajectory and chemical signature, the 'invaders'
stood out clearly.
The youngest stars from Gaia-Enceladus are actually younger than the native
Milky Way stars in what is now the thick-disc region. That means that the
progenitor of the thick disc was already present when the fusion happened,
and Gaia-Enceladus, because of its large size, shook it and puffed it up.
In a previous paper, the team had already described a huge 'blob' of stars
sharing a common origin. Now, it shows that stars from the blob in the halo
are the debris from the merging of the Milky Way with a galaxy which was
slightly more massive than the Small Magellanic Cloud, some ten billion
years ago. That galaxy is called Gaia-Enceladus, after the giant Enceladus
who in Greek mythology was born of Gaia (the Earth goddess) and Uranus (the
Sky god).

KEPLER SPACE TELESCOPE RETIRED
NASA

After nine years in deep space collecting data that indicate our sky to be
filled with billions of hidden planets -- more planets even than stars --
the Kepler space telescope has run out of fuel needed for further science
operations. NASA has decided to retire the spacecraft within its current,
safe orbit, away from the Earth. Kepler leaves a legacy of more than 2,600
planet discoveries from outside the Solar System, many of which could be
promising places for life. Kepler has opened our eyes to the diversity of
planets that exist in our Galaxy. The most recent analysis of Kepler's
discoveries concludes that 20 to 50 per cent of the stars visible in the
night sky are likely to have small, possibly rocky, planets similar in size
to the Earth and located within the habitable zones of their parent stars.
That that means they are located at distances from their parent stars where
liquid water -- a vital ingredient to life as we know it -- might pool on
the planetary surface. The most common size of planet Kepler found does not
exist in the Solar System -- between the sizes of the Earth and Neptune --
and we have much to learn about such planets. Kepler also found that Nature
often produces jam-packed planetary systems, in some cases with so many
planets orbiting close to their parent stars that our own Solar System
looks sparse by comparison. Launched on 2009 March 6, the Kepler space
telescope combined cutting-edge techniques in measuring stellar brightness
with the largest digital camera outfitted for outer-space observations at
that time. Originally positioned to stare continuously at 150,000 stars in
one star-studded patch of the sky in the constellation Cygnus, Kepler took
the first survey of planets in our galaxy and became the agency's first
mission to detect Earth-size planets in the habitable zones of their stars.
Four years into the mission, after the primary mission objectives had been
met, mechanical failures temporarily halted observations. The mission team
was able to devise a fix, switching the spacecraft's field of view roughly
every three months. That enabled an extended mission for the spacecraft,
dubbed K2, which lasted as long as the first mission and raised Kepler's
count of surveyed stars up to more than 500,000. The observation of so many
stars has allowed scientists to understand better their behaviours and
properties, which is critical information in studying the planets that orbit
them. New research into stars with Kepler data also is furthering other
areas of astronomy, such as the history of our Milky Way Galaxy and the
beginning stages of supernovae. The data from the extended mission were
also made available to the public and scientific community immediately,
allowing discoveries to be made at an incredible pace and setting a high bar
for other missions. Scientists are expected to spend a decade or more in
search of new discoveries in the treasure trove of data Kepler is providing.

DAWN MISSION TO ASTEROID BELT COMES TO END
NASA

The Dawn spacecraft has gone silent, ending a historic mission that studied
time capsules from the Solar System's earliest chapter. Dawn has missed
scheduled communications sessions with NASA's Deep Space Network, and
mission managers concluded that the spacecraft finally ran out of hydrazine,
the fuel that enables the spacecraft to control its pointing. Dawn can no
longer keep its antennae trained on the Earth to communicate with mission
control or turn its solar panels to the Sun to recharge. The spacecraft was
launched 11 years ago to visit the two largest objects in the main asteroid
belt. Currently, it is in orbit around the dwarf planet Ceres, where it
will remain for decades. Propelled by ion engines, the spacecraft achieved
many firsts along the way. In 2011, when Dawn arrived at Vesta, the second
largest asteroid in the main belt, the spacecraft became the first to orbit
a body in the region between Mars and Jupiter.
 
Bulletin compiled by Clive Down
(c) 2018 The Society for Popular Astronomy

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3
What's On in Pembrokeshire / Haverfordwest Library opens on 7th December
« on: November 09, 2018, 10:33:51 PM »

4
U3A Walkers / Re: Lawrereny Walk - 3D Video
« on: November 07, 2018, 05:38:49 PM »
We've certainly had a downpour!

5
U3A Walkers / Lawrereny Walk - 3D Video
« on: November 06, 2018, 10:29:49 PM »
Here is another view of our walk on Monday 5th at Lawrenny.

https://my.viewranger.com/viewranger3d/track/OTAzNjI2MQ==?units=imperial

6
 
THE SOCIETY FOR POPULAR ASTRONOMY Electronic News Bulletin No. 479 2018 November 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/
 
EARTH'S DUST-CLOUD SATELLITES CONFIRMED
RAS

A team of Hungarian astronomers may have confirmed two elusive clouds of
dust, in semi-stable points just 400,000 kilometres from the Earth. The
clouds, first reported by and named for Polish astronomer Kazimierz
Kordylewski in 1961, are extraordinarily faint, so their existence is
controversial. The Earth--Moon system has five points of stability where
gravitational forces maintain the relative positions of objects located
there. Two of those so-called Lagrange points, L4 and L5, form an
equilateral triangle with the Earth and Moon, and move around the Earth as
the Moon moves along its orbit. L4 and L5 are not completely stable, as
they are disturbed by the gravitational pull of the Sun. Nonetheless they
are thought to be locations where interplanetary dust might collect, at
least temporarily. Kordylewski observed two nearby clusters of dust at L5
in 1961, with various reports since then, but their extreme faintness makes
them difficult to detect and many scientists doubted their existence. In a
paper earlier this year the Hungarian team modelled the Kordylewski clouds
to assess how they form and how they might be detected. The researchers
were interested in their appearance with polarising filters, which transmit
light with a particular direction of oscillation, similar to those in some
types of sunglasses; scattered or reflected light is always more or less
polarised, depending on the angle of scattering or reflection. They then
set out to find the dust clouds. With a linearly polarising filter system
attached to a camera lens and CCD detector, the scientists took exposures of
the purported location of the Kordylewski cloud at the L5 point. The images
they obtained show polarised light reflected from dust, extending well
outside the field of view of the camera lens.
The observed pattern matches predictions made by the same group of
researchers in an earlier paper and is consistent with the earliest
observations of the Kordylewski clouds 60 years ago. Astronomers were able
to rule out optical artefacts and other effects, so the presence of the dust
cloud is confirmed. The Kordylewski clouds are two of the toughest objects
to find, and though they are as close to the Earth as the Moon are largely
overlooked by researchers in astronomy. It is intriguing to confirm that
our planet has dusty pseudo-satellites in orbit alongside our lunar
neighbour. Given their stability, the L4 and L5 points are seen as
potential sites for orbiting space probes, and as transfer stations for
missions exploring the wider Solar System. There are also proposals to
store pollutants at the two points. Future research will look at L4 and L5,
and the associated Kordylewski clouds, to understand how stable they really
are, and whether their dust presents any kind of threat to equipment and
future astronauts.
 
MOON TO REVEAL SECRETS OF THE EARLY UNIVERSE
RAS

The Moon may be the key to unlocking how the first stars and galaxies shaped
the early Universe. A team of astronomers observed the Moon with a radio
telescope to help search for the faint signal from hydrogen atoms. Before
there were stars and galaxies, the Universe was pretty much just hydrogen,
floating around in space. Since there are no sources of the optical light
visible to our eyes, that early stage of the Universe is known as the
'cosmic dark ages'. The astronomers describe how they have used the
Murchison Widefield Array (MWA) radio telescope to help search for radio
signals given off by the hydrogen atoms.
The radio signal from the early Universe is very weak compared to the
extremely bright objects in the foreground, which include accreting black
holes in other galaxies and electrons in our own Milky Way. The key to
solving that problem is being able precisely to measure the average
brightness of the sky. However, built-in effects from the instruments and
radio-frequency interference make it difficult to get accurate observations
of the very faint radio signal. In their work, the astronomers used the
Moon as a reference point of known brightness and shape. That allowed them
to measure the brightness of the Milky Way at the position of the occulting
Moon. The astronomers also took into account 'earthshine' radio waves from
the Earth that reflect off the Moon and back onto the telescope. Earthshine
corrupts the signal from the Moon and the team had to remove that contam-
ination from their analysis. If astronomers can detect that radio signal it
will tell us whether our theories about the evolution of the Universe are
correct. With more observations, the astronomers hope to uncover the
hydrogen signal and put theoretical models of the Universe to the test.

A CHRISTMAS COMET
Spaceweather.com

Astronomers are calling Comet 46P/Wirtanen the "comet of the year". Seven
weeks from now, on Dec. 16, the kilometre-wide ball of dirty ice will come
within 11.5 million km of the Earth -- making it one of the 10 closest-
approaching comets of the Space Age. Comet 46P/Wirtanen will probably
become a naked-eye object for several weeks around Christmas. Pictures
taken with a 12-inch telescope show the comet's green atmosphere which is,
impressively, almost twice the angular size of the planet Jupiter. The
green colour comes from diatomic carbon (C2) -- a gaseous substance common
in comet atmospheres that glows green in the near-vacuum of space. At the
moment, the integrated brightness of the comet is similar to that of a
10th-magnitude star. However, it is expected to brighten more than 200-fold
by December. If current trends hold, 46P could ultimately reach magnitude
+3, making it not a Great Comet but a very good one, visible to the unaided
eye and an easy target for binoculars or small telescopes. Comet Wirtanen
passes through the inner Solar System every 5.4 years. Right now it is near
the orbit of Mars, and is heading in our direction.

ULTRA-CLOSE STARS INSIDE PLANETARY NEBULA
RAS

Astronomers have discovered two stars in a binary pair that complete an
orbit around one another in a little over three hours, residing in the
planetary nebula M3-1. Remarkably, the stars could drive a nova explosion,
an entirely unexpected event according to current understanding of binary-
star evolution. Planetary nebulae are the glowing shells of gas and dust
formed from the outer layers of stars like our own Sun, which they throw off
during the final stages of their evolution. In many cases, interaction with
a nearby companion star plays an important role in the ejection of that
material and the formation of the elaborate structures seen in the resulting
planetary nebulae. The planetary nebula M3-1 is located in the constella-
tion Canis Major, at a distance of roughly 14,000 light-years. M3-1 was a
firm candidate to host a binary central star, as its structure with prom-
inent jets and filaments is typical of binary-star interactions. Using the
telescopes of the European Southern Observatory in Chile, the team looked
at M3-1 over a period of several years. In the process they discovered and
studied the binary star in the centre of the nebula.
The two stars are so close together that they cannot be resolved from the
ground, so instead the presence of the second star is inferred from the
variation of their observed combined brightness -- most obviously by
periodic eclipses of one star by the other, which produce marked drops in
the brightness. The team discovered that the central star of the planetary
nebula M3-1 has one of the shortest orbital periods of binary central stars
known to date, at just over three hours. The ESO observations also show
that the two stars -- most likely a white dwarf with a low-mass main-
sequence companion -- are almost touching. As a result, the pair is likely
to undergo a nova eruption, the result of the transfer of material from one
star to the other. When the recipient star reaches a critical mass, a
violent thermonuclear explosion takes place and the system temporarily
increases in brightness by up to a million times. Theory suggests that
binary stars should be well separated after the formation of a planetary
nebula. It should then take a long time before they begin to interact again
and events such as novae become possible. In 2007, astronomers observed a
different nova explosion, known as Nova Vul 2007, inside another planetary
nebula. The 2007 event was particularly difficult to explain. By the time
the two stars are close enough for a nova, the material in the planetary
nebula should have expanded and dissipated so much that it is no longer
visible. The new event adds to the conundrum. Among the stars in the
centre of M3-1, there is another candidate for a similar nova eruption in
the relatively near future.

SUPERMASSIVE BLACK HOLE MERGERS
RAS

New research has found evidence for a large number of double supermassive
black holes, probably precursors of gigantic black-hole merging events.
That confirms the current understanding of cosmological evolution -- that
galaxies and their associated black holes merge over time, forming bigger
and bigger galaxies and black holes. Astronomers have looked at radio maps
of powerful jet sources and found signs that would usually be present when
looking at black holes that are closely orbiting each other. Before black
holes merge they form a binary black hole, where the two black holes orbit
around one another. Gravitational-wave telescopes have been able to record
the merging of smaller black holes since 2015, by measuring the strong
bursts of gravitational waves that are emitted when binary black holes
merge, but current technology cannot be used to demonstrate the presence of
supermassive binary black holes. Supermassive black holes emit powerful
jets. When supermassive binary black holes orbit, they cause the jet
emanating from the nucleus of a galaxy periodically to change its direction.
Astronomers studied the directions in which such jets are emitted, and
variances in those directions; they compared the direction of the jets with
that of one of the radio lobes (that store all the particles that ever went
through the jet channels) to demonstrate that that method can be used to
indicate the presence of supermassive binary black holes. The fact that
the most powerful jets are associated with binary black holes could have
important consequences for the formation of stars in galaxies: stars form
from cold gas, jets heat that gas and thus suppress the formation of stars.
A jet that always heads in the same direction only heats a limited amount of
gas in its vicinity. However, jets from binary black holes change direction
continuously. Therefore, they can heat much more gas, suppressing the
formation of stars much more efficiently, and thus contributing towards
keeping the number of stars in galaxies within the observed limits.

KIN OF GRAVITATIONAL-WAVE SOURCE DISCOVERED
University of Maryland

On 2017 October 16, an international group of astronomers and physicists
excitedly reported the first simultaneous detection of light and
gravitational waves from the same source -- a merger of two neutron stars.
Now, a of astronomers has identified a direct relative of that historic
event. The newly described object, named GRB150101B, was reported as a
gamma-ray burst localized by NASA's Neil Gehrels Swift Observatory in 2015.
Follow-up observations suggest that GRB150101B shares remarkable similari-
ties with the neutron-star merger, named GW170817, discovered by the Laser
Interferometer Gravitational-wave Observatory (LIGO) and observed by
multiple light-gathering telescopes in 2017. A new study suggests that
those two separate objects may, in fact, be directly related. The team
suspects that both GRB150101B and GW170817 were produced by the same type of event: a merger of two neutron stars. Such catastrophic coalescences each generated a narrow jet, or beam, of high-energy particles. The jets each
produced a short, intense gamma-ray burst (GRB) -- a powerful flash that
lasts only a few seconds. GW170817 also created ripples in space-time
called gravitational waves, suggesting that that might be a common feature
of neutron-star mergers. The apparent match between GRB150101B and GW170817 is striking: both produced an unusually faint and short-lived gamma-ray burst and both were sources of bright, blue optical light and long-lasting
X-ray emission. The host galaxies are also remarkably similar, according to
HST observations. Both are bright elliptical galaxies with a population of
stars a few billion years old that display no evidence of new star
formation.
In the cases of both GRB150101B and GW170817, the explosion was probably
viewed 'off-axis', that is, with the jet not pointing directly towards the
Earth. So far, those events are the only two off-axis short GRBs that
astronomers have identified. The optical emission from GRB150101B is
largely in the blue portion of the spectrum, providing an important clue
that that event is another kilonova, as seen in GW170817. A kilonova is a
luminous flash of radioactive light that produces large quantities of
important elements like silver, gold, platinum and uranium. While there are
many commonalities between GRB150101B and GW170817, there are two very
important differences. One is their location: GW170817 is relatively close,
at about 130 million light-years from the Earth, while GRB150101B lies about
1.7 billion light-years away. The second important difference is that,
unlike GW170817, gravitational-wave data do not exist for GRB150101B.
Without that information, the team cannot calculate the masses of the two
objects that merged. It is possible that the event resulted from the merger
of a black hole and a neutron star, rather than two neutron stars. It is
possible that a few mergers like the ones seen in GW170817 and GRB150101B,
have been detected previously, but were not properly identified using
complementary observations in different wavelengths of light, according to
the researchers. Without such detections -- in particular, at longer
wavelengths such as X-rays or optical light -- it is very difficult to
determine the precise location of events that produce gamma-ray bursts. In
the case of GRB150101B, astronomers at first thought that the event might
coincide with an X-ray source detected by Swift in the centre of the galaxy.
The most likely explanation for such a source would be a supermassive black
hole devouring gas and dust. However, follow-up observations with Chandra
placed the event further away from the centre of the host galaxy. According
to the researchers, even if LIGO had been operational in early 2015, it
would very likely not have detected gravitational waves from GRB150101B
because of the event's greater distance from the Earth. All the same, every
new event observed with both LIGO and multiple light-gathering telescopes is
likely to fit important new pieces into the puzzle.

LARGEST GALAXY PROTO-SUPERCLUSTER FOUND
ESO

A team of astronomers has used the VIMOS instrument on the Very Large
Telescope (VLT) to identify a gigantic proto-supercluster of galaxies
forming in the early Universe, just 2.3 billion years after the Big Bang.
That structure, which the researchers nicknamed Hyperion, is the largest and
most massive structure to be found so early in the formation of the
Universe. The enormous mass of the proto-supercluster is calculated to be
more than 10 to the 15 times that of the Sun. That titanic mass is similar
to that of the largest structures observed in the Universe today, but
finding such a massive object in the early Universe surprised astronomers.
Located in the COSMOS field in the constellation Sextans, Hyperion was
identified by analyzing the vast amount of data obtained from the VIMOS
Ultra-deep Survey which provides a 3D map of the distribution of over 10,000
galaxies in the distant Universe. The team found that Hyperion has a very
complex structure, containing at least 7 high-density regions connected by
filaments of galaxies, and its size is comparable to that of nearby super-
clusters, though it has a very different structure. Superclusters closer to
the Earth tend to have a much more concentrated distribution of mass, with
clear structural features. But in Hyperion, the mass is distributed much
more uniformly in a series of connected blobs, populated by loose associa-
tions of galaxies. That contrast is most likely due to the fact that nearby
super-clusters have had billions of years for gravity to gather matter
together into denser regions -- a process that has been acting for far less
time in the much younger Hyperion. Given its size so early in the history
of the Universe, Hyperion is expected to evolve into something similar to
the immense structures in the local Universe such as the superclusters
making up the Sloan Great Wall or the Virgo Supercluster that contains our
own galaxy, the Milky Way. Understanding Hyperion and how it compares to
similar recent structures may give insights into how the Universe developed
in the past and will evolve into the future, and allow us the opportunity to
challenge some models of supercluster formation.

HUBBLE SPACE TELESCOPE BACK IN ACTION
Cornell University

The Hubble Space Telescope has resumed normal operations after an anxious
few weeks when it looked as if the stalwart spacecraft was on its last legs.
Hubble reported itself offline on its Twitter account early in October and
NASA explained that the craft had entered safe mode after one of the three
gyroscopes used to point and steady the telescope had failed. According to
the space agency, the gyro that failed had been "exhibiting end-of-life
behaviour", which is no surprise given that Hubble was originally a 15-year
mission and has now been scanning the Universe for over 28 years. A backup
enhanced gyro should have seamlessly taken over when the original failed,
but it initially refused to perform, at a level required for operations,
after being switched off for 7.5 years. To get it going again, Hubble
technicians basically instructed the telescope to jiggle around so as to
shake any blockages out of the gyro, and then switched it off and on again
and into different modes a few times. That strategy worked, and Hubble
returned to normal operations on October 26.
Hubble's life-span is now almost twice what was originally intended, and its
successor, the James Webb Space Telescope, will be capable of feats that
Hubble can only dream of. However, the powerful new spacecraft has been
beset by delays over the last 20 years and its launch date has been
postponed once again from May 2020 to March 2021. The project has over-run
its budget many times over and NASA now believes the end total will creep
over $8bn. If that happens, the agency will have to apply for re-author-
ization from Congress for the space telescope. That might seem like an
astronomical sum to pay to further our understanding of the Universe, but
the James Webb could potentially revolutionize that understanding by making
observations of the earliest moments after the Big Bang and examining our
Solar System and nearby exoplanets in detail that has been impossible until
now. In the meantime, however, scientists are still reliant on booking time
with observatories like Hubble.

SPACECRAFT MAKES RECORD CLOSE APPROACH TO THE SUN
Spaceweather.com

NASA's Parker Solar Probe is now closer to the Sun than any other spacecraft
in history, breaking the previous record of 26.6 million miles set by the
Helios 2 spacecraft in 1976. The probe is now well inside the orbit of
Mercury. At closest approach, the solar disc will seem 6 times wider than
it does from the Earth, as the probe is hit by "brutal heat and radiation".
Parker's carbon-composite heat shield is expected to heat up to 2000 deg. F.
The prime mission is to investigate the origin of the solar wind -- a project
best done uncomfortably close to the star. Parker will trace the solar wind
back to its source and find out how it escapes the Sun's gravity and
magnetic confinement. The probe's wide-field camera system, WISPR, can
actually see the solar wind, allowing it to image clouds and shock waves as
they approach and pass the spacecraft. Other sensors on the spacecraft will
sample the structures that WISPR sees, making measurements of particles and
fields that researchers can use to test competing theories. Parker will
plunge towards the Sun 24 more times in the next 8 years.
 
Bulletin compiled by Clive Down
(c) 2018 The Society for Popular Astronomy
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7
Astronomy Group / Re: The Night Sky this month - November
« on: November 02, 2018, 05:33:03 PM »
Orion over Funchal, Madeira, 7.00am 20th October 2018


8
Astronomy Group / The Night Sky this month - November
« on: November 02, 2018, 07:46:11 AM »


As November arrives, northern stargazers enjoy earlier sunsets and longer (if cooler) stargazing sessions, while southern-hemisphere stargazers now enjoy the warmer nights of spring. For deep-sky observers, there are plenty of open star clusters in Cassiopeia and Perseus, and lots of galaxies in Pegasus, Sculptor, and elsewhere. Orion rises well into the evening and dominates the southern sky after midnight, while the stars of northern spring rise before dawn. The bright planets Mars, Jupiter, and Saturn are past their prime for the year, but Venus rises earlier each day in the eastern sky before dawn and puts on a dazzling show. Add in a couple of meteor showers and a favourable chance to see an ancient crater over the lunar limb, and it makes for a good month of stargazing. Here’s what to see in the night sky this month.

Download "The night Sky in November below:

9
What's On in Pembrokeshire / National Park Archaeology Day
« on: October 27, 2018, 03:00:21 PM »

10
Health and Well-being! / New Later Life Care website
« on: October 27, 2018, 10:20:37 AM »
New "Which" Later Life Care website:

Later Life Care website has launched, replacing Which? Elderly Care. You’ll find guidance and information to help you make informed choices around finding, arranging and financing care for you, or a loved one, as you get older.

Take a look at the new site:
https://www.which.co.uk/later-life-care/home-care/later-life-care-formerly-elderly-care-avw1j6w6z7tc



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