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The SOCIETY for POPULAR ASTRONOMY
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Electronic News Bulletin No. 236 2008 January 20
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Here is the latest round-up of news from the Society for Popular
Astronomy. The SPA is Britain's liveliest astronomical society, with
members all over the world. We accept subscription payments online
using 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://tinyurl.com/kogyx



RECENT FIREBALLS
By Alastair McBeath, SPA Meteor Section Director

Two very bright fireballs have been spotted from the UK since the turn
of the year. The first probably passed somewhere above northern
England, at around 18:55-19:00 UT on January 9-10, reported by
observers in Edinburgh, Lincolnshire, Cambridgeshire and Suffolk so
far. The second was near 22:57 UT on January 15-16, seen from at least
six sites scattered across south Wales and southern England. Details
are sketchy at present, but the early reports suggest this meteor was
possibly heading roughly west to east high over southern England,
perhaps near or off the south coast. More details and web-links to
some of the initial reports can be found on the SPA's Recent Fireball
Sightings page, at: http://tinyurl.com/2fg9oh

More observations of either fireball, or any others (a fireball is a
meteor that reaches at least magnitude -3), would be welcomed by the
SPA Meteor Section. If you have not yet done so, please forward me a
full report as soon as possible. The minimum details I need are:

1) Exactly where you were (name of nearest town or large village, plus
latitude and longitude ideally);

2) The date and timing of the event; and

3) Where the fireball started and ended in the sky, as accurately as
possible, or where the first and last points you could see of the
trail were if you didn't see the whole flight.

More advice and a fuller set of details to send are outlined on the
"Fireball Observing" page of the SPA website, at:
http://tinyurl.com/l62fh .


QUADRANTIDS
By Alastair McBeath, SPA Meteor Section Director

As the "Quadrantids 2008" topic on the SPA's Observing Forum has
suggested (at: http://tinyurl.com/2drjbb ), conditions across the UK
seem to have been very poor for the Quadrantids in the opening days of
the year, and no positive visual reports from the shower's expected
maximum night have yet arrived from any British site. While radio
meteor observations are not so troubled by simple clouds, the analysis
of those results has proved less straightforward than we might have
hoped as well. Assistant Meteor Director David Entwistle's assessment
based on six Radio Meteor Observation Bulletin datasets (see:
http://www.rmob.org ) indicated that Quadrantid activity built rapidly
from about 16h UT on January 3, and then continued at a generally
sustained level till around 19h UT on January 4, after which rates
quickly dropped away. Within the day-long period of probably higher
activity over January 3 to 4, there may have been a number of
sub-peaks, but this could not be established with certainty. The six
datasets, one in North America, the rest in Europe, suggested a
possible main peak sometime between roughly 03:30-08:30 UT on January
4, but this was not well-confirmed, due to considerable scatter
between the individual results, even though the mean of these timings
was approximately 05:30 UT, tolerably close to the expected maximum
around 06:40 UT (see ENB 234, archived at: http://tinyurl.com/2ytmfe
on the SPA Forum).

The International Meteor Organization's, IMO's, "live" Quadrantids
webpage (available off the homepage, at: http://www.imo.net ) has been
indicating a lower than usual maximum Zenithal Hourly Rate, ZHR, for
the shower in 2008 so far, with an ill-defined peak ZHR of about 80
+/- 8 persisting from maybe 08h-11h UT on January 4. Rates were above
half this peak value from at least 00h-12h UT on January 4, according
to these preliminary findings. Why there should have been such an
apparent discrepancy between the initial visual and radio reports is
not clear, and will need further investigation.


URSIDS UPDATE
By Alastair McBeath, SPA Meteor Section Director

Details on what the Ursids may or may not have done in late 2007
remain about as open to debate as in the previous ENB,
http://tinyurl.com/yw4gff , but I wanted to correct the impression the
IMO "live" Ursids page was suggesting when I prepared last time's
Ursid comments, that ZHRs of ~20-35 may have persisted from around
11h-22h UT on December 22-23. The "live" webpage was amended soon
after I wrote those notes, as it seems some observations may have been
entered with an incorrect timing, returning the possible visual peak
to lasting for a few hours centred on 21:15 UT only. Further
investigation of the RMOB radio results has still shown no sign of a
clear Ursid maximum in 2007 at all however, with activity reported by
some systems apparently not dissimilar on December 21, 22 or 23.
Investigations continue!


HUBBLE REPAIR PLANS
NASA

NASA has given details on the Space Shuttle's final mission to
refurbish the Hubble telescope with new instruments, batteries,
gyroscopes, and other fixes that with any luck should keep it
operational until 2013. The 11-day mission is scheduled to take place
in August and features five space-walks which will be recorded by an
IMAX camera. There will also be an attempt to repair two existing
instruments -- the 'Advanced Camera for Surveys', which was the
telescope's most-used instrument until it failed last year, and the
'Space Telescope Imaging Spectrograph', which failed in 2004.

Hubble is in dire need of new gyroscopes and batteries. The gyros,
last replaced in 1999, have been the telescope's Achilles heel. While
astronomers prefer operating Hubble with three working gyros, they
have been managing with only two, leaving a pair as backups that can
be pressed into service if the others fail.

The new instruments are the Cosmic Origins Spectrograph, or COS, and
the Wide Field Camera 3, or WFC3. COS is intended to explore how the
'cosmic web' -- the filamentary structure of the Universe at large
scales -- evolved over billions of years and what role it plays in
galaxy formation. WFC3 will allow Hubble to take wide-field images in
a broad range of wavelengths.


ANCESTORS OF MILKY WAY-TYPE GALAXIES
Penn State University

Astronomers using the Multi-Wavelength Survey by Yale and Chile -- a
five-year-old census of galaxies in the early Universe -- have
discovered ancestors of spiral galaxies like our Milky Way. The
ancient objects, some of the first galaxies ever to form, are being
observed as they looked when the Universe was two billion years old.
They are quite small -- one-tenth the size and one-twentieth the mass
of our Milky Way. From the evidence of the Lyman-alpha line emitted
in the ultraviolet by ionised hydrogen, it is clear that the galaxies
must have had many massive hot stars to produce the ionisation.


LIGO SHEDS LIGHT ON COSMIC EVENT BY NOT SEEING IT
California Institute of Technology

An analysis by the international LIGO (Laser-Interferometer
Gravitational- Wave Observatory) collaboration has excluded one
previously leading explanation for the origin of an intense gamma-ray
burst that occurred last winter. On 2007 February 1, the Konus-Wind,
Integral, Messenger, and Swift gamma-ray satellites measured a short
but intense outburst of energetic gamma-rays originating in the
direction of M31. During the intense blast of gamma rays, the LIGO
interferometers at Hanford were operating, but did not register any
gravitational waves. The burst occurred along a line of sight that
was consistent with an origin in one of Andromeda's spiral arms, and a
binary coalescence event, the merger of two neutron stars or black
holes, for example, was considered among the most likely explanations.
Such a monumental cosmic event occurring in a nearby galaxy should
have generated gravitational waves that would be easily measured by
the LIGO detectors. The absence of a gravitational-wave signal meant
that the burst could not have originated in that way in Andromeda.
Other causes for the event, such as a soft gamma-ray repeater or a
binary merger at a much greater distance, are now the most likely
contenders.


'BLUE BLOBS' ARE ISOLATED STAR CLUSTERS
ESA

Hubble has shown that the 'blue blobs' seen in a wispy bridge of gas
called Arp's Loop between the galaxies M81 and M82 are clusters of
stars less than 200 million years old. Many of the stars are only 10
million years old or even younger. Such clusters, with masses of tens
of thousands of solar masses, have not been seen in detail before in
such sparse locations. They are more massive than most open clusters
found inside galaxies, but only a fraction of the masses of globular
star clusters that orbit a galaxy. Because the clusters do not belong
to any particular galaxy, the heavy elements that their stars produce
get expelled into intergalactic space, perhaps explaining how the
Universe was seeded with heavy elements early in its history.


HISTORY OF SOLAR SYSTEM IN COMET DUST
University of Minnesota

Four years ago, the Stardust spacecraft collected grains of dust
blowing off the nucleus of Comet Wild-2. After testing helium and
neon trapped in the dust specks, researchers report that although the
comet itself formed in the icy fringes of the Solar System, the dust
appears to have been formed close to the young Sun and bombarded by
intense radiation from those and other gases before being flung out
beyond Neptune and trapped in the comet, but how any of that could
have happened noone knows.


GALAXY'S POSITRON CLOUD IS LOP-SIDED
ESA

People at the Max Planck Institute for Extra-terrestrial Physics and
an international team of astronomers have been studying four years'
data from the orbiting gamma-ray observatory Integral. Gamma-rays
with an energy of 511 thousand electron-volts (keV) have been recorded
coming from the central regions of the Galaxy. That particular energy
is known to be the signature of the mutual annihilation of electrons
and their 'anti-matter' counterpart, positrons. The origin of the
positrons has been in doubt ever since the discovery of the 511-keV
emission from the centre of the Galaxy by gamma-ray detectors flown on
balloons during the 1970s. From earlier results based on fewer data,
the positron cloud seemed to be spherical and centred on the centre of
the Galaxy. Such a shape and position corresponds to the supposed
distribution of dark matter in the centre of our Galaxy, so it was
suggested that dark matter was somehow creating pairs of electrons and
positrons, which then annihilated to produce the gamma-rays. The new
results, however, point away from dark matter as the origin of the
positrons. Beyond the Galactic Centre, the cloud is not spherical but
lop-sided. Its distribution appears to agree with that of a
population of a particular type of binary stars, known as hard
(because they emit at high energies) low-mass X-ray binaries; the
similarity has been held to suggest that the binaries are responsible
for most of the positrons.


ASTEROID WILL MISS MARS
New Scientist

The initial orbit determination of a 50-m asteroid discovered on 2007
November 20 gave it a 1 in 75 chance of striking Mars on January 30,
but further observations show that it will pass some 4000 km from the
planet.


OLDEST COSMIC EXPLOSION DETECTED
Topix

Astronomers using the Swift satellite and the Gemini Observatory have
detected a cosmic explosion that took place 7.4 billion years ago --
making it the oldest known short gamma-ray burst. It came from almost
twice as far away as any previous one. GRBs are among the most
powerful explosions in the Universe, releasing enormous amounts of
energy in the form of X-rays and gamma-rays. Most short GRBs are
thought to occur when two neutron stars collide and collapse into a
black hole, emitting energy in two oppositely- directed beams.


PLANETS FORM TWICE FOR OLD STARS
BBC News

Two old stars appear to be rejuvenated, according to a recent study.
The two stars -- known as BP Psc and Tycho 4144 329 2 -- possess many
signatures characteristic of young stars, including the active, rapid
accretion of gas, an extended orbiting disc of dust and gas, excess
emission in the infrared spectrum and -- in the case of BP Psc -- jets
of gas being fired off into space. After star-formation, the dust and
gas left over is supposed gradually to form planetesimals, such as
comets and asteroids, as well as planets, so on that basis dusty discs
ought to belong to stars that are young. Young stars are expected
also to have significant amounts of the element lithium, which has
appreciable abundance in the interstellar medium and in meteorites but
is destroyed at the temperatures of stellar interiors, so its
abundance is small or undetectable in most stars other than newly
formed ones. The amount of lithium in BP Psc is found to be low, as
if it were an old star. In addition, there does not appear to be any
molecular cloud nearby that could have formed the star at all
recently. The Tycho star has a companion which allowed astronomers to
ascertain that the age of the system was at least 400 million years,
probably more. But how the old stars can appear to be undergoing a
second youth is hard to explain.


MASSIVE BLACK HOLE
BBC News

A black hole 18 billion times more massive than the Sun has been
discovered by Finnish astronomers. It is orbited by another black
hole, and that has allowed its mass to be estimated. The binary
black-hole system powers a quasar called OJ 287 that lies about 3.5
billion light-years away in the constellation of Cancer. It emits a
pulsing light signal, with two major pulses every 12 years. A pulse
was predicted for 2007 September 13 and was duly observed. The
researchers think that, as the holes orbit one another, the less
massive one hits a disc of matter surrounding its companion twice.
The impact releases hot gas which comes out from both sides of the
disc and is the source of the optical pulse.


HYDROGEN CLOUD APPROACHES MILKY WAY
Astronomy

A new study by astronomers at the [US] National Radio Astronomy
Observatory at Green Bank shows that an elongated hydrogen cloud is on
a collision course with the Milky Way. The leading edge of the cloud,
named Smith's Cloud for astronomer Gail Smith, who discovered it in
1963, is already interacting with gas from our Galaxy. It lies south
of the Galactic Centre and spans 15°. If you could see the cloud with
your eyes, it would be a very impressive sight in the night sky,
covering almost as much sky as Orion. The cloud measures 11,000
light-years long and 2,500 light-years wide. It lies 8,000 light-years
from the Milky Way's disc and contains enough hydrogen to make a
million stars like the Sun. It is approaching the Milky Way at about
240 km/s; the team believes that the impact will occur in less than 40
million years, about 90° ahead of the Sun and slightly farther away
from the Galaxy's centre. The cloud has such a low total velocity
that it must always have been bound to the Galaxy rather than being
some intergalactic object.


DOUBLE EINSTEIN RING
Astronomy

The Hubble telescope has identified a previously unseen optical
alignment in space: a pair of glowing rings, one inside the other like
a bulls-eye pattern. The phenomenon, called gravitational lensing,
occurs when a massive galaxy in the foreground bends the light rays
from a distant galaxy behind it. When the galaxies are exactly in
line, the light forms a circle, called an Einstein ring, around the
foreground galaxy. If another background galaxy lies precisely on the
same sight-line, a second, larger ring will appear. In the recently
observed case, the massive foreground galaxy is almost perfectly
aligned in the sky with two background galaxies at different
distances. The foreground galaxy is 3 billion light-years away; the
inner and outer rings are comprised of multiple images of two galaxies
at distances of about 6 and 11 billion light-years. The distribution
of matter in the foreground galaxies that is warping space to create
the gravitational lens can be precisely mapped. Also, the geometry of
the rings allowed the team to estimate the mass of the middle galaxy
at 1 billion solar masses.


COMET 8P/TUTTLE
IAU

Radar imaging of comet 8P/Tuttle, which approached to within 38
million kilometres of Earth in January, has revealed that the nucleus
consists of two components and is possibly a contact binary, with two
roughly spherical lobes measuring approximately 3 and 4 km in
diameter.


MESSENGER FLYBY OF MERCURY
NASA

On January 14 Messenger skimmed 200 km above the surface of Mercury in
the first of three fly-bys of the planet. Initial indications from
the radio signals indicate that the spacecraft is still operating
perfectly. The first scientific data were received just minutes
before the closest approach to the planet, as planned. The spacecraft
is continuing to collect imagery and other scientific measurements as
it leaves Mercury, documenting some previously unseen parts of the
surface. Measurements of the Doppler shift of the signals are
expected to improve knowledge of Mercury's mass and gravity field.
Further fly-bys are due to take place on 2008 October 6 and 2009
September 29, successively slowing down the spacecraft with a view to
enabling it to be inserted into orbit around Mercury on 2011 March 18
to begin a year-long orbital mission.



The SPA Electronic News Bulletins are sponsored by the Open University.

Bulletin compiled by Clive Down

(c) 2008 the Society for Popular Astronomy


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