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The SOCIETY for POPULAR ASTRONOMY
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Electronic News Bulletin No. 276 2009 November 22
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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
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/
LEONIDS - FIRST IMPRESSIONS
By Alastair McBeath, SPA Meteor Section Director
Initial news coming through from this year's Leonid maximum
suggests enhanced activity was indeed seen, but not quite to any of
the predicted stronger-event timings (the possible storm-proportion
rate predictions were heavily revised downwards to merely "good to
strong" shortly after ENB 275 was published, archived at
http://snipurl.com/tcn1s . It is too early for a proper assessment, with
fresh data still arriving continually, but the "live" International Meteor
Organization (IMO) Leonids webpage (at http://snipurl.com/tcn24 ) has
indicated so far that there may have been two peaks with Zenithal
Hourly Rates (ZHRs) of 100 or more on November 17, one for half an
hour or so centred around 20:15 UT (possibly the more active, with
ZHRs of ~110-120), the other for about fifteen minutes between
21:00-21:15 UT (ZHRs ~95-120). The predictions mostly suggested
the highest Leonid activity would occur sometime between 21:00-
22:00 UT, as well as several lesser potential maxima on November 17
and 18. These preliminary ZHR values and timings are, of course,
subject to revision.
Results arriving at the SPA so far have suggested the better skies for
British observers near the expected maxima were on November 16-
17, primarily from parts of central-southern England (Leics, Worcs &
Oxon) and northwest Northern Ireland. November 17-18 seems to have
been a lot poorer for most places, with yet more heavy rain. Some
comments can be found on the Observing Forum's "Leonids" topic, at:
http://snipurl.com/tcn2l . Intriguingly, several UK fireballs have been
reported from November 15-16 and 16-17 so far, a couple of which
appear to have been possible Taurids. However, the most spectacular
was a Leonid at 05:47 UT on November 16-17, as witnessed from
Lancashire and Co. Londonderry. The Northern Ireland observer,
Martin McKenna, estimated it was brighter than full Moon, and left a
persistent train for about ten minutes afterwards! Though not operating
his camera at the critical instant, when the initial surprise wore off,
Martin managed to secure a number of images of the event's train, as
it twisted and changed with time due to high-altitude winds blowing in
different directions only a few vertical kilometres apart. Some of his
images can be seen among the Leonid reports on the UK Weather
World's Space Weather Forum here: http://snipurl.com/tcobn .
Any fresh observations of this fireball, or any others (a fireball is a
meteor of magnitude -3 or brighter), made from the British Isles or
nearby, would be welcomed by the Section. The minimum details
needed are:
1) Exactly where you were (give the name of the nearest town or large
village and county if in Britain, or your geographic latitude and
longitude if elsewhere in the world);
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 did not see the whole flight.
More advice and a fuller set of details to send (including an e-mail
report form) are given on the "Making and Reporting Fireball
Observations" page of the SPA website, at: http://snipurl.com/tcnfi .
Please keep sending in your "ordinary" Leonid observations too!
ORIONIDS 2009
By Alastair McBeath, SPA Meteor Section Director
As followers of the Observing Forum topic on this shower (at
http://snipurl.com/tcmks ) will already know, the Orionids also
produced an enhanced return this year, another in the consecutive
series that began in 2006, and despite generally negative
expectations for 2009 in advance (as discussed in ENB 275). A
belated warning was issued by the IAU for possibly increased Orionid
activity however, circulated just a few days before the expected peak.
Unfortunately, weather conditions across much of the UK were again
rather poor, and very few detailed observations have arrived from here
covering what took place. Luckily though, we were fortunate in
receiving some excellent support from meteor watchers overseas,
including those of the North American Meteor Network (NAMN;
http://www.namnmeteors.org ), data kindly provided very soon after
the event by NAMN leader Mark Davis, and the radio observers who
routinely report to the Radio Meteor Observation Bulletins (RMOBs;
see: http://www.rmob.org ), helpfully submitted by RMOB editor Chris
Steyaert in the form of RMOB 195 for October 2009. Further
comments, including some positive UK reports, can be read on the
UK Weather World's Space Weather Forum "Orionids 2009" topic at:
http://snipurl.com/tcpua . The list of contributing observers to date is as
follows, where "R" means radio and "V" visual results were provided
by that individual.
Salvador Aguirre (Mexico; NAMN; V), Enric Algeciras (Spain; RMOB;
R), "aliblincow" (Scotland; V), Orlando Benitez (Canary Islands; RMOB;
R), Mike Boschat (Nova Scotia, Canada; NAMN, V & RMOB, R), Jeff
Brower (British Columbia, Canada; RMOB; R), Willy Camps (Belgium;
RMOB; R), John Coussens (Belgium; RMOB; R), Tibor Csorgei
(Slovakia; NAMN; V), Mark Davis (South Carolina, USA; NAMN; V),
Gaspard De Wilde (Belgium; RMOB; R), David Entwistle (England;
RMOB; R), Karl-Heinz Gansel (Germany; RMOB; R), William Godley
(Oklahoma, USA; NAMN; V), Richard Hill (North Carolina, USA;
NAMN; V), Javor Kac (Slovenia; NAMN; V), Mike Linnolt (Hawaii, USA;
NAMN; V), Grigoris Maravelias (Crete; NAMN; V), Pierre Martin
(Ontario, Canada; NAMN; V), Paul Martsching (Iowa, USA; NAMN; V),
Alastair McBeath (England; V), Martin McKenna (Northern Ireland; V),
Mike Otte (Illinois, USA; RMOB; R), Jean-Louis Rault (France; RMOB;
R), Steve Roush (Arizona, USA; RMOB; R), Wayne Sanders (British
Columbia, Canada; RMOB; R), Andy Smith (England; RMOB; R), Chris
Steyaert (Belgium; RMOB; R), Wesley Stone (Oregon, USA; NAMN;
V), Dave Swan (England; RMOB; R), Richard Taibi (Maryland, USA;
NAMN; V), Istvan Tepliczky (Hungary; RMOB; R), Dirk Van Hessche
(Belgium; RMOB; R), Felix Verbelen (Belgium; RMOB; R), William
Watson (New York, USA; NAMN; V), Graham Winstanley (England; V),
Kim Youmans (Georgia, USA; NAMN; V).
Orionid activity was not strongly enhanced, but ZHRs between 30-45
persisted from October 19-20 to 23-24, as shown by both the SPA
data, and the more extensive IMO preliminary results. While ZHRs of
about 30 were predicted for this year anyway, their persistence beyond
the normal October 21 maximum date was not. The IMO's "live"
Orionids page is still available off the http://www.imo.net homepage. In
more detail, the IMO dataset has indicated average Orionid ZHRs were
about 35 throughout October 20, 21 and 22. They then seem to have
risen to around 40-45 on October 23, before falling back to ~25 by the
24th, and dropping further thereafter. These values remain preliminary
only however, and may change later after a full analysis.
On October 22, while the enhanced shower activity was still underway,
the IAU were already claiming unusually high rates of bright Orionids
had been seen on October 20. However, this seemed to have been
based on just one observer's data. The SPA magnitude distributions
over the whole of the shower's extended peak (based on 467 Orionids
and 223 sporadics) yielded mean magnitudes, corrected to ideal sky
conditions, of +2.6 and +3.4 respectively, both quite normal statistics,
with no unexpected excess of bright Orionids at all. About 36% of
Orionids left persistent trains, again much as usual.
Assistant Meteor Director David Entwistle and I have examined
various aspects of the radio meteor data during the best from the
Orionids this year, with some additional input from observer-analyst
Jeff Brower, which results overall demonstrated a quite clear Orionid
response, lasting for a week or so centred around October 21-22.
From past years, similar radio meteor behaviour has tended to
indicate above average, but not outstanding, Orionid activity, when
compared with the visual findings. In greater detail, based on from 17
to 21 viable radio datasets a day (8 from North America and 13 from
Europe), a reasonably obvious peak in echo counts due to the
Orionids was registered on October 21, with good activity detected by
most operational systems from October 19 to 23 inclusive, tailing off
into October 24. There was an indication that modestly increased
numbers of brighter meteors (assumed to be from echoes that
produced longer than normal radio reflections) were present from
October 21-24 inclusive, and that similar events may have been
occurring, probably at a somewhat lower rate, from October 19. A
loose "peak" in such longer echoes was suggested as lasting across
both October 22 and 23. There seemed little evidence for a specific
time-dependency beyond the "day" level in all this, as most systems
registered generally increased meteor counts whenever the Orionid
radiant was clear of the horizon on the dates above. It has not been
possible to check so readily for these 'radio-bright' meteors during the
Orionids before, thus it is not certain how significant this aspect may be.
As always, some caution needs to be exercised when considering
radio meteor results, because of the considerable difficulties in
carrying out the analyses, but this is our best attempt at a full examination.
Many thanks go to all our contributing observers and correspondents
during the shower - with particular commiserations to those whose
watching was thwarted by the weather.
AUTUMN FIREBALLS UPDATE
By Alastair McBeath, SPA Meteor Section Director
Since the previous ENB, the autumn had been a relatively quiet one for
fireball sightings reported to the Section, until close to the Leonid
maxima, as noted above, probably because of some very unhelpful
British skies overnight during the last couple of months. Our Recent
Fireball Sightings page at: http://snipurl.com/tcoc3 , has continued to be
updated with what reports have come through. Interestingly - and
thankfully! - the number of "sky lanterns" mistaken for meteoric fireballs
has fallen significantly in recent weeks, presumably as people realise
meteors need a clear sky to be seen in, not the UK's persistent clouds!
A couple of fireballs in October were of particular note, though not seen
from the British Isles. The first was a spectacular detonating daylight
event on October 8, at about 03:00 UT (around 11 a.m. local time) over
the islands of Indonesia, which produced a blast wave that was
detected by a number of infrasound detectors there. These detections
enabled the object's atmospheric location to be determined as high
above the city of Bone in southern Sulawesi. SPA and UK Weather
World Forum topics at http://snipurl.com/tcpyj and http://snipurl.com/tcpz0
respectively had links to more information, including a published report
on the event.
Closer to home, a very bright fireball was imaged from the Netherlands
around 18:00 UT on October 13-14, enabling Dutch Meteor Society
analysts to estimate a trajectory for the object. David Entwistle's
posting near the end of the SPA Observing Forum topic at
http://snipurl.com/tcoca gave a link to the DMS's webpage, where
more details can be found.
METEOR SECTION WEBPAGE UPGRADE COMPLETED
By Alastair McBeath, SPA Meteor Section Director
October saw the completion of the Section's webpage upgrade, which
has been on-going throughout IYA2009. Aside from a few fresh tweaks
to existing pages, this final stage also saw the revision of the "Coping
with very high meteor activity" page, in anticipation of the potential for
a Leonid storm this month. As noted above, that prediction had
evaporated before the amended page had gone online, but the
information is something all meteor observers need to be aware of, in
case unexpectedly strong meteor rates should appear one night when
nothing is predicted. This page and all the Section's others can be
accessed from the Meteor homepage, at: http://snipurl.com/tcqat .
INTERNATIONAL METEOR CONFERENCE 2010 - IN BRITAIN!
By Alastair McBeath, SPA Meteor Section Director
For the first time, the International Meteor Conference (IMC) is to be
held in the British Isles, from September 16 to 19, 2010, at Armagh in
Northern Ireland, organized by IMO members currently working as
professional astronomers at the famous Armagh Observatory. Details
are still being finalized for bookings and costs, but registration is
expected to open early in the New Year, and it is anticipated that the
price to attend, which will include all Conference sessions, the
excursion, full-board accommodation (in the Armagh City Youth Hostel),
and a copy of the meeting's Proceedings, will be around 150 Euros.
More information can be found on the IMC 2010 webpage,
http://www.imo.net/imc2010 , while photos and notes from past IMCs
can be found elsewhere on the IMO website. The IMC's official
language is English, and all meteor enthusiasts, amateur or
professional, will be welcome to attend.
PROSPECTS FOR THE 2009 GEMINIDS
By Alastair McBeath, SPA Meteor Section Director
IYA2009's last major shower, the Geminids, have a moonless
maximum expected on December 14 around 05h UT. New Moon is on
December 16. The Geminid radiant rises around sunset and reaches
a usefully-observable elevation for meteor watchers by about 20h UT
from Britain. After this, it remains well-placed for the rest of the night,
culminating around 02h. Highest ZHRs should be ~120 judging by
recent returns, and observed rates from the UK on December 13-14
under clear, very dark skies could be a meteor a minute or more
throughout the post-midnight hours, if its activity is of this strength again.
This is because Geminid rates often remain close to their maximum
levels for 6 to 10 hours to either side of their best, and activity is
normally good, if lower, for a night or two before, and sometimes a night
after, the maximum in an average year. Thus pleasing shower rates
may be glimpsed then, even if clouds intervene on the peak night.
Geminids are medium speed and often bright meteors, though few
leave glowing persistent trains after them. Much lower Geminid rates
may be seen away from the maximum in any moonless skies available
between roughly December 7 to 17. For more information on
December's meteor activity as a whole, and a Geminid radiant chart,
see our December meteor activity webpage at: http://snipurl.com/tcqqi .
Good luck, and clear skies!
NEAR MISS ASTEROIDS
IAU
On Nov. 6 at 2132 UT, asteroid 2009 VA passed the Earth just 14,000 km
above the surface, well inside the distance of geosynchronous
satellites. If it had hit, the ~6-metre space rock would have
disintegrated in the atmosphere as a spectacular fireball, causing no
significant damage to the ground. 2009 VA was discovered just 15
hours before closest approach by astronomers working at the Catalina
Sky Survey. In early October, with no warning, a ~10-metre asteroid
hit the atmosphere above Indonesia and exploded. The break-up was so
powerful that it triggered nuclear-test-ban sensors thousands of
kilometres away. A just-released analysis of infrasound data shows
that the asteroid detonated with an energy equivalent to about 50,000
tons of TNT, similar to that of a `small' atomic bomb.
SPACECRAFT SEE 'DAMP MOON SOILS'
BBC News
Data from three spacecraft, including India's Chandrayaan probe, show
that very fine films of water coat the particles that make up the
lunar soil. The rock and soil samples returned by the Apollo missions
were found to be ever so slightly 'damp' when examined in the
laboratory, but scientists could never rule out the possibility that
the water in the samples got in only after they were brought back to
Earth. The only safe scientific conclusion they could draw at the
time was that the lunar surface was all-but bone dry. Now a remote
sensing instrument on Chandrayaan-1, India's first mission to lunar
orbit, has confirmed that there is a real water signal at the Moon.
Two other satellites looking at the Moon -- the US Deep Impact probe
and the US--European Cassini spacecraft -- confirm the Chandrayaan
findings. Both collected their Moon data long ago (in the case of
Cassini, 10 years ago), but the significance of what they saw is only
now being realised. The quantity of water is seen to increase the
closer the observations are made to the poles -- the very places the
Apollo missions never went. Scientists suspect the water is created
in the soil in an interaction with the solar wind, fast-moving
particles that constantly stream away from the Sun. Harsh space
radiation triggers a chemical reaction in which oxygen atoms already
in the soil acquire hydrogen nuclei to make water molecules and the
simpler hydrogen-oxygen (OH) molecule.
Researchers have also said that preliminary data from the 'Lunar
Crater Observation and Sensing Satellite' (LCROSS) indicate that water
exists in a permanently shadowed lunar crater. On Oct. 9, the LCROSS
spacecraft and a companion rocket stage made twin impacts in crater
Cabeus near the Moon's south pole. A plume of debris travelled at a
high angle beyond the rim of Cabeus and into sunlight, while an
additional curtain of debris was ejected more laterally. Evidence of
water was seen in both the high-angle vapour plume and the ejecta
curtain created by the impact.
PREVIOUSLY UNSEEN TERRITORY ON MERCURY OBSERVED
Science Daily
The MESSENGER spacecraft's third fly-by of Mercury has given
scientists, for the first time, an almost complete view of the
planet's surface and revealed some dramatic changes in Mercury's
comet-like tail. The spacecraft's cameras and instruments revealed 6%
of the planet's surface never before seen at close range, One of the
spacecraft's instruments conducted its most extensive observations to
date of Mercury's ultra-thin atmosphere or 'exosphere'. Material in
the exosphere comes mainly from the surface of Mercury, knocked aloft
by solar radiation, solar-wind bombardment and meteoroid vaporization.
The wispy gaseous envelope is stretched by solar radiation pressure
into a long, comet-like tail, which seems to be changing as Mercury
moves round the Sun.
The observations also show that calcium and magnesium in the exosphere
exhibit different seasonal changes from sodium -- a difference that
researchers do not understand. After MESSENGER enters Mercury orbit
in 2011, it can make a continuous study of seasonal changes in all
exospheric constituents. That will provide key information on the
relative importance of the processes that generate, sustain, and
modify Mercury's atmosphere. Approximately 98% of Mercury's surface
has now been imaged. After MESSENGER goes into orbit, it will see the
polar regions, which are the only remaining unobserved areas of the
planet.
ORIGIN OF MARS' REDNESS
RAS
The widespread idea that Mars is red owing to rocks being rusted by
the water that once flooded the planet may not be correct. Recent
laboratory studies show that red dust may be formed by the ongoing
grinding of surface rocks, and liquid water need not have played any
significant role in the formation process. Mars should really look
blackish, between its white polar caps, because most of the rocks at
mid-latitudes are basalt. Accurate knowledge of the composition and
mineralogy of the planet is vital in understanding the structure and
evolution of the near-surface environment and its interaction with the
atmosphere, as well as in searching for potential habitats on Mars.
Fine red dust covers Mars' surface and is even present in the
atmosphere, dominating the weather and sometimes becoming so thick
that it plunges the planet into darkness.
In a recent laboratory study, scientists at the Mars Simulation
Laboratory used a novel technique to simulate sand transport on Mars.
They sealed sand (quartz) samples in glass flasks and mechanically
tumbled them for several months, turning each flask ten million times.
After gently tumbling pure quartz sand for seven months, almost 10% of
the sand had been reduced to dust. When scientists added powdered
magnetite, an iron oxide present in Martian basalt, to the flasks they
were surprised to see it getting redder as the flasks were tumbled.
Reddish-orange material deposits, which resemble mineral mantles
known as desert varnish, started appearing on the tumbled flasks.
Subsequent analysis of the flask material and dust has shown that the
magnetite was transformed into the red mineral haematite, through a
completely mechanical process without the presence of water. The
scientists suspect that, as the quartz sand grains are tumbled around,
they get quickly eroded and an alteration of minerals through contact
ensues. The first experiments show that this process occurs not only
in air but also in a dried carbon dioxide atmosphere, i.e. in
conditions that resemble those occurring on Mars.
SATELLITES OF JUPITER AND (50000) QUAOAR
IAU
The IAU has approved a new designation and name for the 50th confirmed
satellite of Jupiter, S/2003 J 17, which was re-discovered this past
August. What a pity that the name is not recorded here! The IAU has
also approved the name 'Weywot' for the satellite of the trans-
neptunian minor planet (50000) Quaoar.
SPITZER DISCOVERS SATURN'S LARGEST RING
NASA
Scientists using the Spitzer space telescope have discovered an
enormous and previously unknown infrared ring around Saturn. If the
ring could be seen in the night sky, it would span the width of two
Full Moons. The new belt lies at the far reaches of the Saturnian
system, with an orbit tilted 27 degrees from the main ring plane. The
bulk of its material starts about six million kilometres away from the
planet and extends outward roughly another 12 million kilometres. One
of Saturn's furthest moons, Phoebe, circles within the new-found ring,
and is probably the source of its material. The ring is tenuous,
consisting of widely dispersed particles of ice and dust. Spitzer's
infrared camera was able to observe the glow of the cool dust, which
has a temperature of only about 80 Kelvin.
The discovery may help to solve a long-standing riddle of one of
Saturn's moons. Iapetus has a strange appearance -- one side is
bright and the other is really dark. Cassini first noticed the moon
in 1671, and years later realized it has a dark side, now named
Cassini Regio in his honour. Saturn's outsize ring could explain how
Cassini Regio came to be so dark. The ring is circling in the same
direction as Phoebe, while Iapetus, the other rings and most of
Saturn's moons are all going the opposite way. According to the
scientists, some of the dark and dusty material from the outer ring
moves inward toward Iapetus and collides with it, blackening the
leading hemisphere (like our Moon, Iapetus remains in a fixed
orientation with respect to its orbital travel).
Astronomers have also discovered a satellite orbiting within the outer
B ring in Saturn's rings. The satellite, designated 2009 S 1,
protrudes above the rings by approximately 150 m; the inferred
diameter of the satellite, assuming an orbit co-planar with the ring
material, is consequently approximately 300 m.
EXOPLANETS CLUE TO SUN'S CURIOUS CHEMISTRY
ESO
Astronomers have found that Sun-like stars that host planets have
destroyed their lithium much more efficiently than 'planet-free'
stars. For almost 10 years astronomers have tried to find out what
distinguishes stars with planetary systems from their barren cousins.
They have now found that the amount of lithium in Sun-like stars
depends on whether or not they have planets. The low abundance of
lithium in the Sun, as compared to otherwise similar stars, has been
known for some time but not understood.
The astronomers made an analysis of 500 stars, including 70 planet-
hosting ones. Most of the stars were monitored for several years with
the 'High-Accuracy Radial-Velocity Planet Searcher' (HARPS) attached
to ESO's 3.6-metre telescope. The astronomers looked in particular at
Sun-like stars, almost a quarter of the whole sample. They found that
the majority of stars hosting planets possess less than 1% of the
amount of lithium shown by most of the other stars. Unlike most other
elements lighter than iron, the light nuclei of lithium, beryllium and
boron are not normally produced in significant amounts in stars.
Instead, it is thought that lithium, composed of just three protons
and four neutrons, was mainly produced just after the Big Bang, 13.7
billion years ago. Most stars will thus have the same amount of
lithium, unless they have destroyed it themselves. It seems still not
to have been explained why having planets would destroy lithium. But
the empirical result promises to provide astronomers with an effective
way to search for planetary systems -- low-lithium stars are worthy of
further significant observing efforts.
ETA CARINAE
IAU
Astronomers using the Hubble telescope report that the central star in
Eta Carina has recently brightened to magnitude 5.1. It now accounts
for half of the total light seen in the Homunculus nebula, compared to
less than 10% before 1995. Eta Carinae is one of the most massive and
luminous stars in our galaxy, and is suspected to be a binary system
with a period of 5.54 years. In 1822, the star brightened to 2nd
magnitude, and in 1827 to 1st magnitude. Fifteen years later it
outshone all stars in the sky apart from Sirius. It then faded to 8th
magnitude in 1900 but has slowly been getting brighter since then.
Such massive stars have a lifetime of only one million years and Eta
Carinae is expected to end its life as a supernova within the next
100,000 years or so.
NEW CLASS OF EXPLODING STAR
University of California, Berkeley
An unusual supernova rediscovered in 7-year-old data may be a new type
of exploding star. The supernova was detected in 2002 in the galaxy
NGC 1821, in the constellation Lepus, by the Katzman Automatic Imaging
Telescope (KAIT) at Lick Observatory as well as by amateur
astronomers, but at the time it was erroneously classified as a common
Type II supernova. Now it has been realized to be an unusual kind of
supernova more akin to a Type Ia. The spectrum had been obtained with
the Keck I telescope, 7 days after discovery. Follow-up images made
by KAIT showed that the brightness of SN 2002bj dropped off so
rapidly that the supernova disappeared from sight 20 days after its
discovery. An image of that area of the sky taken seven days prior to
discovery showed no supernova, so it had brightened and dimmed into
obscurity in less than 27 days, whereas most supernovae brighten and
dim over 3 to 4 months.
The supernova's rapidity, coupled with its faintness, the strong
signature of helium in the spectrum of the explosion, and the absence
of hydrogen points toward helium detonation on a white dwarf.
A suggested theoretical explanation involves AM Canum Venaticorum
(AM CVn) binary systems, which are composed of two white dwarfs, one
of which is primarily made of helium that is being slowly transferred
onto its companion. White dwarfs are stars that have burned their
hydrogen down to carbon and oxygen or, in some particular cases, to
helium. In AM CVn systems, when enough helium has been accumulated on
the surface of the primary white dwarf, an explosion occurs; but the
explosion is nothing like a regular Type Ia explosion because the
white dwarf survives the detonation of the helium shell instead of
being totally disrupted. The event has similarities to both a nova
and a supernova. Novae occur when hydrogen falls onto a star and
accumulates in a shell that can flare up as brief thermonuclear
explosions. SN 2002bj is a 'super' nova, generating about 1,000 times
the energy of a standard nova.
SHEDDING LIGHT ON THE COSMIC SKELETON
ESO
Matter is not distributed uniformly in the Universe. In our cosmic
vicinity, stars form in galaxies, and galaxies usually form groups and
clusters. Some cosmological theories would like matter also to
clump on a still larger scale in the so-called 'cosmic web', in which
galaxies are embedded in filaments stretching between voids. The
filaments are millions of light-years long and constitute the skeleton
of the Universe: galaxies gather around them, and galaxy clusters form
at their intersections. Scientists do not know how they would swirl
into existence. Although massive filamentary structures have been
observed at relatively small distances from us, solid proof of their
existence in the more distant Universe has been lacking.
Now astronomers have discovered a large structure around a cluster of
galaxies about seven billion light-years away. They have studied the
structure in some detail, estimating the distances of over 150
galaxies, and hence obtaining a three-dimensional view of the
structure. They have identified several groups of galaxies
surrounding the main cluster and were able to distinguish tens of such
clumps, each typically ten times as massive as our own Milky Way
galaxy (some as much as a thousand times more massive), while they
estimate that the mass of the cluster amounts to at least ten thousand
times the mass of the Milky Way.
RAPID STAR FORMATION IN YOUNG GALAXIES
RAS
According to scientists at Durham University, 'stellar nurseries'
within the first galaxies gave birth to stars at a much more rapid
rate than previously supposed. The research looked back 12.5 billion
years to one of the most distant known galaxies, seen as it appeared
about one billion years after the Big Bang. Taking advantage of
gravitational lensing, the scientists observed the rapid bursts of
star formation in the galaxy, called MS1358arc. Within the star-
forming regions, new stars were being created at a rate of about 50
stars per year -- around 100 times faster than had been previously
thought.
The researchers say that the galaxy, which measures 6,000 light years
across, has all the characteristics that would allow it to evolve into
a galaxy such as our Milky Way. Given the size of the star-forming
regions, we would expect it to be forming stars at a rate of about one
Sun per year, but it seems to be much more active than that.
'MOST DISTANT' GALAXY GROUP OBSERVED
NASA
Astronomers using the Chandra X-Ray Observatory have discovered a
group of galaxies at a record distance. The cluster, named JKCS041,
is 10.2 billion light-years away -- a billion light-years further away
than the previous record holder. Galaxy clusters are the Universe's
largest objects bound by gravity, and experts hope that the findings
will help them understand better how the cosmos has changed over time.
Scientists think that JKCS041 is at the farthest point at which galaxy
clusters could exist in the early Universe. They do not believe that
gravity can work fast enough to make galaxy clusters much earlier, but
have detected what they believe to be the light from individual
galaxies out to about 13 billion light-years.
SIGNATURE OF ANTI-MATTER DETECTED IN LIGHTNING
National Geographic
Designed to scan the heavens thousands to billions of light-years
beyond the Solar System for gamma rays, the Fermi gamma-ray space
telescope has also detected 17 gamma-ray flashes associated with
terrestrial storms, and some of those flashes have contained a
surprising signature of anti-matter. During two recent lightning
storms, Fermi recorded gamma-ray emissions of a particular energy that
could have been produced only by the decay of energetic positrons, the
anti-matter equivalent of electrons. The observations are the first
of their kind for lightning storms. The 17 flashes Fermi detected
occurred just before, during and immediately after lightning strikes,
as tracked by the World-Wide Lightning Location Network.
During lightning storms previously observed by other spacecraft,
energetic electrons moving toward the craft slowed down and produced
gamma rays. The unusual positron signature seen by Fermi suggests that
the normal orientation for an electric field associated with a
lightning storm somehow reversed, Modellers are now trying to dream up
how the field reversal could have occurred. Recording gamma-ray
flashes -- which might harm aeroplanes in storms -- isn't new; the
first were found by Compton in the early 1990s, and the RHESSI
satellite, which primarily looks at X-ray and gamma-ray emissions from
the Sun, has found some 800 terrestrial gamma-ray flashes.
NASA AND ESA SIGN MARS AGREEMENT
BBC News
The US and European space agencies have signed a 'letter of intent'
that ties their Mars programmes together. The agreement allows
scientists and engineers to begin the joint planning of missions. The
union will start with a European-led orbiter in 2016, and continue
with surface rovers in 2018, and perhaps a network of landers in 2018.
The ultimate aim is a mission to return Mars rock and soils.
Bulletin compiled by Clive Down
(c) 2009 the Society for Popular Astronomy
The SOCIETY for POPULAR ASTRONOMY
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Electronic News Bulletin No. 276 2009 November 22
====================================================
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
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/
LEONIDS - FIRST IMPRESSIONS
By Alastair McBeath, SPA Meteor Section Director
Initial news coming through from this year's Leonid maximum
suggests enhanced activity was indeed seen, but not quite to any of
the predicted stronger-event timings (the possible storm-proportion
rate predictions were heavily revised downwards to merely "good to
strong" shortly after ENB 275 was published, archived at
http://snipurl.com/tcn1s . It is too early for a proper assessment, with
fresh data still arriving continually, but the "live" International Meteor
Organization (IMO) Leonids webpage (at http://snipurl.com/tcn24 ) has
indicated so far that there may have been two peaks with Zenithal
Hourly Rates (ZHRs) of 100 or more on November 17, one for half an
hour or so centred around 20:15 UT (possibly the more active, with
ZHRs of ~110-120), the other for about fifteen minutes between
21:00-21:15 UT (ZHRs ~95-120). The predictions mostly suggested
the highest Leonid activity would occur sometime between 21:00-
22:00 UT, as well as several lesser potential maxima on November 17
and 18. These preliminary ZHR values and timings are, of course,
subject to revision.
Results arriving at the SPA so far have suggested the better skies for
British observers near the expected maxima were on November 16-
17, primarily from parts of central-southern England (Leics, Worcs &
Oxon) and northwest Northern Ireland. November 17-18 seems to have
been a lot poorer for most places, with yet more heavy rain. Some
comments can be found on the Observing Forum's "Leonids" topic, at:
http://snipurl.com/tcn2l . Intriguingly, several UK fireballs have been
reported from November 15-16 and 16-17 so far, a couple of which
appear to have been possible Taurids. However, the most spectacular
was a Leonid at 05:47 UT on November 16-17, as witnessed from
Lancashire and Co. Londonderry. The Northern Ireland observer,
Martin McKenna, estimated it was brighter than full Moon, and left a
persistent train for about ten minutes afterwards! Though not operating
his camera at the critical instant, when the initial surprise wore off,
Martin managed to secure a number of images of the event's train, as
it twisted and changed with time due to high-altitude winds blowing in
different directions only a few vertical kilometres apart. Some of his
images can be seen among the Leonid reports on the UK Weather
World's Space Weather Forum here: http://snipurl.com/tcobn .
Any fresh observations of this fireball, or any others (a fireball is a
meteor of magnitude -3 or brighter), made from the British Isles or
nearby, would be welcomed by the Section. The minimum details
needed are:
1) Exactly where you were (give the name of the nearest town or large
village and county if in Britain, or your geographic latitude and
longitude if elsewhere in the world);
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 did not see the whole flight.
More advice and a fuller set of details to send (including an e-mail
report form) are given on the "Making and Reporting Fireball
Observations" page of the SPA website, at: http://snipurl.com/tcnfi .
Please keep sending in your "ordinary" Leonid observations too!
ORIONIDS 2009
By Alastair McBeath, SPA Meteor Section Director
As followers of the Observing Forum topic on this shower (at
http://snipurl.com/tcmks ) will already know, the Orionids also
produced an enhanced return this year, another in the consecutive
series that began in 2006, and despite generally negative
expectations for 2009 in advance (as discussed in ENB 275). A
belated warning was issued by the IAU for possibly increased Orionid
activity however, circulated just a few days before the expected peak.
Unfortunately, weather conditions across much of the UK were again
rather poor, and very few detailed observations have arrived from here
covering what took place. Luckily though, we were fortunate in
receiving some excellent support from meteor watchers overseas,
including those of the North American Meteor Network (NAMN;
http://www.namnmeteors.org ), data kindly provided very soon after
the event by NAMN leader Mark Davis, and the radio observers who
routinely report to the Radio Meteor Observation Bulletins (RMOBs;
see: http://www.rmob.org ), helpfully submitted by RMOB editor Chris
Steyaert in the form of RMOB 195 for October 2009. Further
comments, including some positive UK reports, can be read on the
UK Weather World's Space Weather Forum "Orionids 2009" topic at:
http://snipurl.com/tcpua . The list of contributing observers to date is as
follows, where "R" means radio and "V" visual results were provided
by that individual.
Salvador Aguirre (Mexico; NAMN; V), Enric Algeciras (Spain; RMOB;
R), "aliblincow" (Scotland; V), Orlando Benitez (Canary Islands; RMOB;
R), Mike Boschat (Nova Scotia, Canada; NAMN, V & RMOB, R), Jeff
Brower (British Columbia, Canada; RMOB; R), Willy Camps (Belgium;
RMOB; R), John Coussens (Belgium; RMOB; R), Tibor Csorgei
(Slovakia; NAMN; V), Mark Davis (South Carolina, USA; NAMN; V),
Gaspard De Wilde (Belgium; RMOB; R), David Entwistle (England;
RMOB; R), Karl-Heinz Gansel (Germany; RMOB; R), William Godley
(Oklahoma, USA; NAMN; V), Richard Hill (North Carolina, USA;
NAMN; V), Javor Kac (Slovenia; NAMN; V), Mike Linnolt (Hawaii, USA;
NAMN; V), Grigoris Maravelias (Crete; NAMN; V), Pierre Martin
(Ontario, Canada; NAMN; V), Paul Martsching (Iowa, USA; NAMN; V),
Alastair McBeath (England; V), Martin McKenna (Northern Ireland; V),
Mike Otte (Illinois, USA; RMOB; R), Jean-Louis Rault (France; RMOB;
R), Steve Roush (Arizona, USA; RMOB; R), Wayne Sanders (British
Columbia, Canada; RMOB; R), Andy Smith (England; RMOB; R), Chris
Steyaert (Belgium; RMOB; R), Wesley Stone (Oregon, USA; NAMN;
V), Dave Swan (England; RMOB; R), Richard Taibi (Maryland, USA;
NAMN; V), Istvan Tepliczky (Hungary; RMOB; R), Dirk Van Hessche
(Belgium; RMOB; R), Felix Verbelen (Belgium; RMOB; R), William
Watson (New York, USA; NAMN; V), Graham Winstanley (England; V),
Kim Youmans (Georgia, USA; NAMN; V).
Orionid activity was not strongly enhanced, but ZHRs between 30-45
persisted from October 19-20 to 23-24, as shown by both the SPA
data, and the more extensive IMO preliminary results. While ZHRs of
about 30 were predicted for this year anyway, their persistence beyond
the normal October 21 maximum date was not. The IMO's "live"
Orionids page is still available off the http://www.imo.net homepage. In
more detail, the IMO dataset has indicated average Orionid ZHRs were
about 35 throughout October 20, 21 and 22. They then seem to have
risen to around 40-45 on October 23, before falling back to ~25 by the
24th, and dropping further thereafter. These values remain preliminary
only however, and may change later after a full analysis.
On October 22, while the enhanced shower activity was still underway,
the IAU were already claiming unusually high rates of bright Orionids
had been seen on October 20. However, this seemed to have been
based on just one observer's data. The SPA magnitude distributions
over the whole of the shower's extended peak (based on 467 Orionids
and 223 sporadics) yielded mean magnitudes, corrected to ideal sky
conditions, of +2.6 and +3.4 respectively, both quite normal statistics,
with no unexpected excess of bright Orionids at all. About 36% of
Orionids left persistent trains, again much as usual.
Assistant Meteor Director David Entwistle and I have examined
various aspects of the radio meteor data during the best from the
Orionids this year, with some additional input from observer-analyst
Jeff Brower, which results overall demonstrated a quite clear Orionid
response, lasting for a week or so centred around October 21-22.
From past years, similar radio meteor behaviour has tended to
indicate above average, but not outstanding, Orionid activity, when
compared with the visual findings. In greater detail, based on from 17
to 21 viable radio datasets a day (8 from North America and 13 from
Europe), a reasonably obvious peak in echo counts due to the
Orionids was registered on October 21, with good activity detected by
most operational systems from October 19 to 23 inclusive, tailing off
into October 24. There was an indication that modestly increased
numbers of brighter meteors (assumed to be from echoes that
produced longer than normal radio reflections) were present from
October 21-24 inclusive, and that similar events may have been
occurring, probably at a somewhat lower rate, from October 19. A
loose "peak" in such longer echoes was suggested as lasting across
both October 22 and 23. There seemed little evidence for a specific
time-dependency beyond the "day" level in all this, as most systems
registered generally increased meteor counts whenever the Orionid
radiant was clear of the horizon on the dates above. It has not been
possible to check so readily for these 'radio-bright' meteors during the
Orionids before, thus it is not certain how significant this aspect may be.
As always, some caution needs to be exercised when considering
radio meteor results, because of the considerable difficulties in
carrying out the analyses, but this is our best attempt at a full examination.
Many thanks go to all our contributing observers and correspondents
during the shower - with particular commiserations to those whose
watching was thwarted by the weather.
AUTUMN FIREBALLS UPDATE
By Alastair McBeath, SPA Meteor Section Director
Since the previous ENB, the autumn had been a relatively quiet one for
fireball sightings reported to the Section, until close to the Leonid
maxima, as noted above, probably because of some very unhelpful
British skies overnight during the last couple of months. Our Recent
Fireball Sightings page at: http://snipurl.com/tcoc3 , has continued to be
updated with what reports have come through. Interestingly - and
thankfully! - the number of "sky lanterns" mistaken for meteoric fireballs
has fallen significantly in recent weeks, presumably as people realise
meteors need a clear sky to be seen in, not the UK's persistent clouds!
A couple of fireballs in October were of particular note, though not seen
from the British Isles. The first was a spectacular detonating daylight
event on October 8, at about 03:00 UT (around 11 a.m. local time) over
the islands of Indonesia, which produced a blast wave that was
detected by a number of infrasound detectors there. These detections
enabled the object's atmospheric location to be determined as high
above the city of Bone in southern Sulawesi. SPA and UK Weather
World Forum topics at http://snipurl.com/tcpyj and http://snipurl.com/tcpz0
respectively had links to more information, including a published report
on the event.
Closer to home, a very bright fireball was imaged from the Netherlands
around 18:00 UT on October 13-14, enabling Dutch Meteor Society
analysts to estimate a trajectory for the object. David Entwistle's
posting near the end of the SPA Observing Forum topic at
http://snipurl.com/tcoca gave a link to the DMS's webpage, where
more details can be found.
METEOR SECTION WEBPAGE UPGRADE COMPLETED
By Alastair McBeath, SPA Meteor Section Director
October saw the completion of the Section's webpage upgrade, which
has been on-going throughout IYA2009. Aside from a few fresh tweaks
to existing pages, this final stage also saw the revision of the "Coping
with very high meteor activity" page, in anticipation of the potential for
a Leonid storm this month. As noted above, that prediction had
evaporated before the amended page had gone online, but the
information is something all meteor observers need to be aware of, in
case unexpectedly strong meteor rates should appear one night when
nothing is predicted. This page and all the Section's others can be
accessed from the Meteor homepage, at: http://snipurl.com/tcqat .
INTERNATIONAL METEOR CONFERENCE 2010 - IN BRITAIN!
By Alastair McBeath, SPA Meteor Section Director
For the first time, the International Meteor Conference (IMC) is to be
held in the British Isles, from September 16 to 19, 2010, at Armagh in
Northern Ireland, organized by IMO members currently working as
professional astronomers at the famous Armagh Observatory. Details
are still being finalized for bookings and costs, but registration is
expected to open early in the New Year, and it is anticipated that the
price to attend, which will include all Conference sessions, the
excursion, full-board accommodation (in the Armagh City Youth Hostel),
and a copy of the meeting's Proceedings, will be around 150 Euros.
More information can be found on the IMC 2010 webpage,
http://www.imo.net/imc2010 , while photos and notes from past IMCs
can be found elsewhere on the IMO website. The IMC's official
language is English, and all meteor enthusiasts, amateur or
professional, will be welcome to attend.
PROSPECTS FOR THE 2009 GEMINIDS
By Alastair McBeath, SPA Meteor Section Director
IYA2009's last major shower, the Geminids, have a moonless
maximum expected on December 14 around 05h UT. New Moon is on
December 16. The Geminid radiant rises around sunset and reaches
a usefully-observable elevation for meteor watchers by about 20h UT
from Britain. After this, it remains well-placed for the rest of the night,
culminating around 02h. Highest ZHRs should be ~120 judging by
recent returns, and observed rates from the UK on December 13-14
under clear, very dark skies could be a meteor a minute or more
throughout the post-midnight hours, if its activity is of this strength again.
This is because Geminid rates often remain close to their maximum
levels for 6 to 10 hours to either side of their best, and activity is
normally good, if lower, for a night or two before, and sometimes a night
after, the maximum in an average year. Thus pleasing shower rates
may be glimpsed then, even if clouds intervene on the peak night.
Geminids are medium speed and often bright meteors, though few
leave glowing persistent trains after them. Much lower Geminid rates
may be seen away from the maximum in any moonless skies available
between roughly December 7 to 17. For more information on
December's meteor activity as a whole, and a Geminid radiant chart,
see our December meteor activity webpage at: http://snipurl.com/tcqqi .
Good luck, and clear skies!
NEAR MISS ASTEROIDS
IAU
On Nov. 6 at 2132 UT, asteroid 2009 VA passed the Earth just 14,000 km
above the surface, well inside the distance of geosynchronous
satellites. If it had hit, the ~6-metre space rock would have
disintegrated in the atmosphere as a spectacular fireball, causing no
significant damage to the ground. 2009 VA was discovered just 15
hours before closest approach by astronomers working at the Catalina
Sky Survey. In early October, with no warning, a ~10-metre asteroid
hit the atmosphere above Indonesia and exploded. The break-up was so
powerful that it triggered nuclear-test-ban sensors thousands of
kilometres away. A just-released analysis of infrasound data shows
that the asteroid detonated with an energy equivalent to about 50,000
tons of TNT, similar to that of a `small' atomic bomb.
SPACECRAFT SEE 'DAMP MOON SOILS'
BBC News
Data from three spacecraft, including India's Chandrayaan probe, show
that very fine films of water coat the particles that make up the
lunar soil. The rock and soil samples returned by the Apollo missions
were found to be ever so slightly 'damp' when examined in the
laboratory, but scientists could never rule out the possibility that
the water in the samples got in only after they were brought back to
Earth. The only safe scientific conclusion they could draw at the
time was that the lunar surface was all-but bone dry. Now a remote
sensing instrument on Chandrayaan-1, India's first mission to lunar
orbit, has confirmed that there is a real water signal at the Moon.
Two other satellites looking at the Moon -- the US Deep Impact probe
and the US--European Cassini spacecraft -- confirm the Chandrayaan
findings. Both collected their Moon data long ago (in the case of
Cassini, 10 years ago), but the significance of what they saw is only
now being realised. The quantity of water is seen to increase the
closer the observations are made to the poles -- the very places the
Apollo missions never went. Scientists suspect the water is created
in the soil in an interaction with the solar wind, fast-moving
particles that constantly stream away from the Sun. Harsh space
radiation triggers a chemical reaction in which oxygen atoms already
in the soil acquire hydrogen nuclei to make water molecules and the
simpler hydrogen-oxygen (OH) molecule.
Researchers have also said that preliminary data from the 'Lunar
Crater Observation and Sensing Satellite' (LCROSS) indicate that water
exists in a permanently shadowed lunar crater. On Oct. 9, the LCROSS
spacecraft and a companion rocket stage made twin impacts in crater
Cabeus near the Moon's south pole. A plume of debris travelled at a
high angle beyond the rim of Cabeus and into sunlight, while an
additional curtain of debris was ejected more laterally. Evidence of
water was seen in both the high-angle vapour plume and the ejecta
curtain created by the impact.
PREVIOUSLY UNSEEN TERRITORY ON MERCURY OBSERVED
Science Daily
The MESSENGER spacecraft's third fly-by of Mercury has given
scientists, for the first time, an almost complete view of the
planet's surface and revealed some dramatic changes in Mercury's
comet-like tail. The spacecraft's cameras and instruments revealed 6%
of the planet's surface never before seen at close range, One of the
spacecraft's instruments conducted its most extensive observations to
date of Mercury's ultra-thin atmosphere or 'exosphere'. Material in
the exosphere comes mainly from the surface of Mercury, knocked aloft
by solar radiation, solar-wind bombardment and meteoroid vaporization.
The wispy gaseous envelope is stretched by solar radiation pressure
into a long, comet-like tail, which seems to be changing as Mercury
moves round the Sun.
The observations also show that calcium and magnesium in the exosphere
exhibit different seasonal changes from sodium -- a difference that
researchers do not understand. After MESSENGER enters Mercury orbit
in 2011, it can make a continuous study of seasonal changes in all
exospheric constituents. That will provide key information on the
relative importance of the processes that generate, sustain, and
modify Mercury's atmosphere. Approximately 98% of Mercury's surface
has now been imaged. After MESSENGER goes into orbit, it will see the
polar regions, which are the only remaining unobserved areas of the
planet.
ORIGIN OF MARS' REDNESS
RAS
The widespread idea that Mars is red owing to rocks being rusted by
the water that once flooded the planet may not be correct. Recent
laboratory studies show that red dust may be formed by the ongoing
grinding of surface rocks, and liquid water need not have played any
significant role in the formation process. Mars should really look
blackish, between its white polar caps, because most of the rocks at
mid-latitudes are basalt. Accurate knowledge of the composition and
mineralogy of the planet is vital in understanding the structure and
evolution of the near-surface environment and its interaction with the
atmosphere, as well as in searching for potential habitats on Mars.
Fine red dust covers Mars' surface and is even present in the
atmosphere, dominating the weather and sometimes becoming so thick
that it plunges the planet into darkness.
In a recent laboratory study, scientists at the Mars Simulation
Laboratory used a novel technique to simulate sand transport on Mars.
They sealed sand (quartz) samples in glass flasks and mechanically
tumbled them for several months, turning each flask ten million times.
After gently tumbling pure quartz sand for seven months, almost 10% of
the sand had been reduced to dust. When scientists added powdered
magnetite, an iron oxide present in Martian basalt, to the flasks they
were surprised to see it getting redder as the flasks were tumbled.
Reddish-orange material deposits, which resemble mineral mantles
known as desert varnish, started appearing on the tumbled flasks.
Subsequent analysis of the flask material and dust has shown that the
magnetite was transformed into the red mineral haematite, through a
completely mechanical process without the presence of water. The
scientists suspect that, as the quartz sand grains are tumbled around,
they get quickly eroded and an alteration of minerals through contact
ensues. The first experiments show that this process occurs not only
in air but also in a dried carbon dioxide atmosphere, i.e. in
conditions that resemble those occurring on Mars.
SATELLITES OF JUPITER AND (50000) QUAOAR
IAU
The IAU has approved a new designation and name for the 50th confirmed
satellite of Jupiter, S/2003 J 17, which was re-discovered this past
August. What a pity that the name is not recorded here! The IAU has
also approved the name 'Weywot' for the satellite of the trans-
neptunian minor planet (50000) Quaoar.
SPITZER DISCOVERS SATURN'S LARGEST RING
NASA
Scientists using the Spitzer space telescope have discovered an
enormous and previously unknown infrared ring around Saturn. If the
ring could be seen in the night sky, it would span the width of two
Full Moons. The new belt lies at the far reaches of the Saturnian
system, with an orbit tilted 27 degrees from the main ring plane. The
bulk of its material starts about six million kilometres away from the
planet and extends outward roughly another 12 million kilometres. One
of Saturn's furthest moons, Phoebe, circles within the new-found ring,
and is probably the source of its material. The ring is tenuous,
consisting of widely dispersed particles of ice and dust. Spitzer's
infrared camera was able to observe the glow of the cool dust, which
has a temperature of only about 80 Kelvin.
The discovery may help to solve a long-standing riddle of one of
Saturn's moons. Iapetus has a strange appearance -- one side is
bright and the other is really dark. Cassini first noticed the moon
in 1671, and years later realized it has a dark side, now named
Cassini Regio in his honour. Saturn's outsize ring could explain how
Cassini Regio came to be so dark. The ring is circling in the same
direction as Phoebe, while Iapetus, the other rings and most of
Saturn's moons are all going the opposite way. According to the
scientists, some of the dark and dusty material from the outer ring
moves inward toward Iapetus and collides with it, blackening the
leading hemisphere (like our Moon, Iapetus remains in a fixed
orientation with respect to its orbital travel).
Astronomers have also discovered a satellite orbiting within the outer
B ring in Saturn's rings. The satellite, designated 2009 S 1,
protrudes above the rings by approximately 150 m; the inferred
diameter of the satellite, assuming an orbit co-planar with the ring
material, is consequently approximately 300 m.
EXOPLANETS CLUE TO SUN'S CURIOUS CHEMISTRY
ESO
Astronomers have found that Sun-like stars that host planets have
destroyed their lithium much more efficiently than 'planet-free'
stars. For almost 10 years astronomers have tried to find out what
distinguishes stars with planetary systems from their barren cousins.
They have now found that the amount of lithium in Sun-like stars
depends on whether or not they have planets. The low abundance of
lithium in the Sun, as compared to otherwise similar stars, has been
known for some time but not understood.
The astronomers made an analysis of 500 stars, including 70 planet-
hosting ones. Most of the stars were monitored for several years with
the 'High-Accuracy Radial-Velocity Planet Searcher' (HARPS) attached
to ESO's 3.6-metre telescope. The astronomers looked in particular at
Sun-like stars, almost a quarter of the whole sample. They found that
the majority of stars hosting planets possess less than 1% of the
amount of lithium shown by most of the other stars. Unlike most other
elements lighter than iron, the light nuclei of lithium, beryllium and
boron are not normally produced in significant amounts in stars.
Instead, it is thought that lithium, composed of just three protons
and four neutrons, was mainly produced just after the Big Bang, 13.7
billion years ago. Most stars will thus have the same amount of
lithium, unless they have destroyed it themselves. It seems still not
to have been explained why having planets would destroy lithium. But
the empirical result promises to provide astronomers with an effective
way to search for planetary systems -- low-lithium stars are worthy of
further significant observing efforts.
ETA CARINAE
IAU
Astronomers using the Hubble telescope report that the central star in
Eta Carina has recently brightened to magnitude 5.1. It now accounts
for half of the total light seen in the Homunculus nebula, compared to
less than 10% before 1995. Eta Carinae is one of the most massive and
luminous stars in our galaxy, and is suspected to be a binary system
with a period of 5.54 years. In 1822, the star brightened to 2nd
magnitude, and in 1827 to 1st magnitude. Fifteen years later it
outshone all stars in the sky apart from Sirius. It then faded to 8th
magnitude in 1900 but has slowly been getting brighter since then.
Such massive stars have a lifetime of only one million years and Eta
Carinae is expected to end its life as a supernova within the next
100,000 years or so.
NEW CLASS OF EXPLODING STAR
University of California, Berkeley
An unusual supernova rediscovered in 7-year-old data may be a new type
of exploding star. The supernova was detected in 2002 in the galaxy
NGC 1821, in the constellation Lepus, by the Katzman Automatic Imaging
Telescope (KAIT) at Lick Observatory as well as by amateur
astronomers, but at the time it was erroneously classified as a common
Type II supernova. Now it has been realized to be an unusual kind of
supernova more akin to a Type Ia. The spectrum had been obtained with
the Keck I telescope, 7 days after discovery. Follow-up images made
by KAIT showed that the brightness of SN 2002bj dropped off so
rapidly that the supernova disappeared from sight 20 days after its
discovery. An image of that area of the sky taken seven days prior to
discovery showed no supernova, so it had brightened and dimmed into
obscurity in less than 27 days, whereas most supernovae brighten and
dim over 3 to 4 months.
The supernova's rapidity, coupled with its faintness, the strong
signature of helium in the spectrum of the explosion, and the absence
of hydrogen points toward helium detonation on a white dwarf.
A suggested theoretical explanation involves AM Canum Venaticorum
(AM CVn) binary systems, which are composed of two white dwarfs, one
of which is primarily made of helium that is being slowly transferred
onto its companion. White dwarfs are stars that have burned their
hydrogen down to carbon and oxygen or, in some particular cases, to
helium. In AM CVn systems, when enough helium has been accumulated on
the surface of the primary white dwarf, an explosion occurs; but the
explosion is nothing like a regular Type Ia explosion because the
white dwarf survives the detonation of the helium shell instead of
being totally disrupted. The event has similarities to both a nova
and a supernova. Novae occur when hydrogen falls onto a star and
accumulates in a shell that can flare up as brief thermonuclear
explosions. SN 2002bj is a 'super' nova, generating about 1,000 times
the energy of a standard nova.
SHEDDING LIGHT ON THE COSMIC SKELETON
ESO
Matter is not distributed uniformly in the Universe. In our cosmic
vicinity, stars form in galaxies, and galaxies usually form groups and
clusters. Some cosmological theories would like matter also to
clump on a still larger scale in the so-called 'cosmic web', in which
galaxies are embedded in filaments stretching between voids. The
filaments are millions of light-years long and constitute the skeleton
of the Universe: galaxies gather around them, and galaxy clusters form
at their intersections. Scientists do not know how they would swirl
into existence. Although massive filamentary structures have been
observed at relatively small distances from us, solid proof of their
existence in the more distant Universe has been lacking.
Now astronomers have discovered a large structure around a cluster of
galaxies about seven billion light-years away. They have studied the
structure in some detail, estimating the distances of over 150
galaxies, and hence obtaining a three-dimensional view of the
structure. They have identified several groups of galaxies
surrounding the main cluster and were able to distinguish tens of such
clumps, each typically ten times as massive as our own Milky Way
galaxy (some as much as a thousand times more massive), while they
estimate that the mass of the cluster amounts to at least ten thousand
times the mass of the Milky Way.
RAPID STAR FORMATION IN YOUNG GALAXIES
RAS
According to scientists at Durham University, 'stellar nurseries'
within the first galaxies gave birth to stars at a much more rapid
rate than previously supposed. The research looked back 12.5 billion
years to one of the most distant known galaxies, seen as it appeared
about one billion years after the Big Bang. Taking advantage of
gravitational lensing, the scientists observed the rapid bursts of
star formation in the galaxy, called MS1358arc. Within the star-
forming regions, new stars were being created at a rate of about 50
stars per year -- around 100 times faster than had been previously
thought.
The researchers say that the galaxy, which measures 6,000 light years
across, has all the characteristics that would allow it to evolve into
a galaxy such as our Milky Way. Given the size of the star-forming
regions, we would expect it to be forming stars at a rate of about one
Sun per year, but it seems to be much more active than that.
'MOST DISTANT' GALAXY GROUP OBSERVED
NASA
Astronomers using the Chandra X-Ray Observatory have discovered a
group of galaxies at a record distance. The cluster, named JKCS041,
is 10.2 billion light-years away -- a billion light-years further away
than the previous record holder. Galaxy clusters are the Universe's
largest objects bound by gravity, and experts hope that the findings
will help them understand better how the cosmos has changed over time.
Scientists think that JKCS041 is at the farthest point at which galaxy
clusters could exist in the early Universe. They do not believe that
gravity can work fast enough to make galaxy clusters much earlier, but
have detected what they believe to be the light from individual
galaxies out to about 13 billion light-years.
SIGNATURE OF ANTI-MATTER DETECTED IN LIGHTNING
National Geographic
Designed to scan the heavens thousands to billions of light-years
beyond the Solar System for gamma rays, the Fermi gamma-ray space
telescope has also detected 17 gamma-ray flashes associated with
terrestrial storms, and some of those flashes have contained a
surprising signature of anti-matter. During two recent lightning
storms, Fermi recorded gamma-ray emissions of a particular energy that
could have been produced only by the decay of energetic positrons, the
anti-matter equivalent of electrons. The observations are the first
of their kind for lightning storms. The 17 flashes Fermi detected
occurred just before, during and immediately after lightning strikes,
as tracked by the World-Wide Lightning Location Network.
During lightning storms previously observed by other spacecraft,
energetic electrons moving toward the craft slowed down and produced
gamma rays. The unusual positron signature seen by Fermi suggests that
the normal orientation for an electric field associated with a
lightning storm somehow reversed, Modellers are now trying to dream up
how the field reversal could have occurred. Recording gamma-ray
flashes -- which might harm aeroplanes in storms -- isn't new; the
first were found by Compton in the early 1990s, and the RHESSI
satellite, which primarily looks at X-ray and gamma-ray emissions from
the Sun, has found some 800 terrestrial gamma-ray flashes.
NASA AND ESA SIGN MARS AGREEMENT
BBC News
The US and European space agencies have signed a 'letter of intent'
that ties their Mars programmes together. The agreement allows
scientists and engineers to begin the joint planning of missions. The
union will start with a European-led orbiter in 2016, and continue
with surface rovers in 2018, and perhaps a network of landers in 2018.
The ultimate aim is a mission to return Mars rock and soils.
Bulletin compiled by Clive Down
(c) 2009 the Society for Popular Astronomy
--
Good Clear Skies
--
Astrocomet
--
Colin James Watling
--
Real Astronomer and head of the Comet section for LYRA (Lowestoft and Great Yarmouth Regional Astronomers) also head of K.A.G (Kessingland Astronomy Group) and Navigator (Astrogator) of the Stars (Fieldwork)
--
Web: http://lyra.freewebsites.com/
Good Clear Skies
--
Astrocomet
--
Colin James Watling
--
Real Astronomer and head of the Comet section for LYRA (Lowestoft and Great Yarmouth Regional Astronomers) also head of K.A.G (Kessingland Astronomy Group) and Navigator (Astrogator) of the Stars (Fieldwork)
--
Web: http://lyra.freewebsites.com/
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