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The SOCIETY for POPULAR ASTRONOMY
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Electronic News Bulletin No. 210 2006 December 10
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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://popastro.c.topica.com/maafrl7abvhLzcixLLVb/



LEONIDS - MORE DETAILS
By Alastair McBeath, SPA Meteor Section Director

Results and other information on the 2006 Leonid return have
continued to arrive since the report in ENB 209. However, what
actually happened during the shower's stronger peak on November
18-19, during the critical 04:00-05:30 UT interval then, remains
unclear. SPA data still supports a mean Zenithal Hourly Rate (ZHR)
of around 50 for the hour centred on 04:45 UT, but it would be
possible to inflate short-interval observed rates within that time to
significantly higher levels than this. This seems to have led to claims
of ZHRs of 100+ in places, though this does not seem to reflect the
initial opinions of other observers in Europe, including Britain. The
fuller, more detailed, global review of information by the International
Meteor Organization is still awaited, which should tell us a lot more,
with luck.

Rather more definitely, the NASA researchers who have been video
observing the dark parts of the Moon for lunar meteoroid impact-
flashes over the past year, as we've mentioned previously in the ENBs,
reported another two such detections probably from Leonid particles,
both on November 17. This brings the tally of such detections to 11
"definites" and one "possible" in twelve months, a level about four
times higher than the imaging team's models had expected in advance.
This has clear implications for the impact risk lunar astronauts or
permanently manned bases on the Moon might encounter, so more
observations will be needed to establish if the team have simply been
lucky so far, or if this higher level of impact-flash activity means the
model needs serious revision. To put this into perspective however, it
is worth remembering that two of the Apollo manned lunar missions
took place during strong meteor showers, without any reported
meteoroidal impact problems. Apollo 12, which mission lasted from
1969 November 14-24, took place during the Leonids that year,
whose peak ZHR was ~140, achieved on November 17 (Apollo 12
was struck by lightning just after lift-off, but the mission was largely
unaffected!), while the last mission, Apollo 17, happened between
1972 December 7-19, during the Geminids, with a ZHR then of
~70-80 on December 13. Details on the latest impact results can be
found at:
http://popastro.c.topica.com/maafrl7abvhLAcixLLVb/ ,
and grateful thanks go to ENB Editor Clive Down for providing initial
details on this.

One further radio detection of a possible fireball around 01:30 UT on
November 18-19, beyond the two such reported last time by David
Entwistle, has come in from Megan Argo at the Jodrell Bank
observatory in Cheshire, during tests with a new forward-scatter
meteor system in preparation there. Whether the three radio detections
were of the same event, and whether any of these were due to the
magnitude -8 Leonid David saw visually at 01:27 UT that night, remain
uncertain.

Other Leonid epoch observers to submit at least some preliminary
results since the list published in the previous ENB have included Clive
Down (south Wales), Jane Mills (Northants), Paul Nicholson (West
Yorks - including radio and visual data), Clive Rogers (West
Midlands - imaging results) and Richard Wright (Yorkshire). Gilberto
Renner, a radio meteor observer in Brazil has sent word to say that
most regrettably, his system had been offline throughout the Leonids
thanks to a power failure.

Many thanks go again to all our contributors so far. If anyone has yet
to submit full details of their Leonid observations this year, please do
so as soon as possible. Details of what to send and where to can be
found via the Meteor Section's homepage at:
http://popastro.c.topica.com/maafrl7abvhLBcixLLVb/ .


AUTUMN FIREBALLS
By Alastair McBeath, SPA Meteor Section Director

A fresh fireball report from October 13-14 has arrived recently, made
from Suffolk, which seems to confirm that there was more than one
such event that night, as suspected from the initial reports reviewed
in ENB 207. The "new" event's timing was around 21:30 UT, while
the other, seen from up to six places in southern England, probably
happened around 20:35-20:45 UT. Details for this "earlier" event
remain unchanged however, and the possibility that a third fireball
may have happened sometime between roughly 19-21h UT then,
cannot be discounted either.

More recently, late November brought a spate of fireball sightings,
including: Nov 23-24, ~03:00-03:15 UT, a bright meteor spotted
from Surrey; Nov 25-26, ~07:15 UT, a bright, very slow event seen
from Hertfordshire (if the observer in question is reading this, please
get in touch with an active e-mail address, as the one you sent has
been rejected as "unrecognised"); Nov 28-29, 19:22 UT, mag -4 or
brighter, seen from Shropshire; and Nov 28-29 again, ~21:34 UT, a
very bright, fragmenting fireball reported from Renfrewshire.

The best-reported so far though was that at 23:02 UT on Nov
27-28, which was seen from three UK sites, in London, Essex and
Surrey, and was also imaged by Klaas Jobse's all-sky fireball patrol
camera at Oostkapelle in Holland too (thanks go to David Entwistle
for forwarding this information). There are two images available from
Klaas' homepage, one an all-sky shot, the other a close-up of just the
fireball's trail. For these, see:
http://popastro.c.topica.com/maafrl7abvhLCcixLLVb/ .
A review of the data available so far suggests the object may have
flown on a roughly NW to SE trajectory over the southern North Sea
to the Strait of Dover, off the Essex, Kent to NE French coasts. A
best-estimate suggests a start point around 90-100 km altitude
around 15-20 km south of The Naze in east Essex, and an end
around 55 km altitude over the sea perhaps 20 km NNE of Calais. If
correct, this would imply an atmospheric path length between 70-85
km, descending at circa 30 degrees from the horizontal. Timing
estimates using data from Klaas' image (his system uses a rotating
shutter, thus allowing an estimate of the visible flight time), allow a
mean atmospheric velocity of between 20-25 km/sec to be computed
for such a path, though this does not allow for any deceleration
caused by the atmosphere. Unfortunately, the path details are only
approximate, as it seems just one UK observer witnessed the trail
close to the actual start of the fireball's path, while another caught
the
end, so these details are subject to modification later, if more results
arrive.

Fireball sightings (meteors of magnitude -3 or brighter) from the UK
or close-by are always welcomed by the Section. Information on
what to send and where to can be found via the "Fireball Observing"
page at: http://popastro.c.topica.com/maafrl7abvhLDcixLLVb/ .


FIRST ANION FOUND IN SPACE
Harvard-Smithsonian Center for Astrophysics

Astronomers have discovered the first negatively charged molecule in
space, identifying it from radio signals that were not identified till
now. While about 130 neutral and 14 positively charged molecules are
known to exist in interstellar space, this is the first negative
molecule, or anion, to be found. By learning more about the rich
broth of chemicals found in interstellar space, astronomers hope to
explain how the young Earth converted those basic ingredients into the
chemicals needed for life. The new finding helps to advance
scientists' understanding of the chemistry of the interstellar medium.

Astronomers were able to identify the molecular anion known as C6H- ,
a linear chain of six carbon atoms with one hydrogen atom at the end
and an extra electron. Such molecules were thought to be extremely
rare because the ultraviolet light that suffuses space easily knocks
electrons off molecules. The large size of C6H-, larger than most
neutral and all positive molecules known in space, may increase its
stability in the harsh cosmic environment. The discovery team first
conducted laboratory experiments to determine what radio frequencies
to use in their search. They then used the Green Bank telescope to
re-observe objects which had previously been noticed to transmit
then-unidentified radio signals at the appropriate frequencies.
They found C6H- in two very different locations -- a shell of gas
surrounding the evolved red giant star IRC +10216 in the constellation
Leo, and the cold molecular cloud TMC-1 in Taurus.


2003 FX128 IS DOUBLE
IAU

Astronomers using the Hubble telescope have discovered that the
trans-neptunian object 2003 FX128 has a slightly smaller companion
measuring 134 km in diameter. The primary object has been given the
name Cero whilst the newly discovered secondary is called Phorcys.
The system orbits the Sun every 1039 years and has an aphelion
distance of 187 AU. Other double trans-neptunian objects receiving
names are Logos for 1997 CQ29 and Zoe for its companion, and Typhon
for 2002 CR_46 and Echidna for its companion.


UNUSUAL GAMMA-RAY BURST
The Register

Astronomers using the Integral gamma-ray satellite have observed a
great eruption of gamma rays in the Galactic Centre. The outburst
was noticed during the first observing session of a new 'key
programme', which dedicates almost four weeks of Integral's observing
time to the Galactic Centre, an obvious object for study because there
are so many potential gamma-ray sources there.

Gamma-ray bursts are notoriously short-lived, but in this case the
source did not fade away almost immediately; it became brighter over
the next few days and then gradually faded over a period of weeks.
The suggested explanation is in terns of a binary system consisting of
a star much like our Sun and a black hole whose immense gravitational
field is tearing material off it layer by layer. The material could
be expected to form an 'accretion disc' around the black hole, but
there is no explanation at present as to why the disc might collapse
onto the black hole and cause the kind of outburst witnessed by
Integral.


METEORITE'S MICROSCOPIC BUBBLES
BBC Online

Tiny hollow spheres or bubbles have been found in the Tagish Lake
meteorite, which was collected immediately after its fall in Canada in
2000 and has been maintained in a frozen state ever since, thus
minimising the potential for terrestrial contamination. Mineralogists
who have been investigating the meteorite have estimated that it
contains billions of the tiny globules, although they have reported on
only 26 of them. The ratios of different isotopes of hydrogen and
nitrogen in the meteorite are very unusual, which suggests that the
structures did not originate on the Earth. The isotopic ratios in
the globules show that they formed at temperatures of about -260C,
near absolute zero. The hollow spheres seem to be empty, but they
have organic molecules on their surfaces. The organic molecules most
likely originated in the cold molecular cloud that gave birth to our
Solar System, or at the outermost reaches of the early Solar System.
It should be pointed out that 'organic' is a technical chemical term
that simply means 'carbon-containing' and carries no implication about
life.


MARS RECONNAISSANCE ORBITER OBSERVES VIKINGS
New Scientist

The new Mars Reconnaissance Orbiter has observed about a dozen
spacecraft (all originating from the Earth) on the Martian surface,
and scientists have been able to identify individual rocks that were
first photographed by the Viking landers in 1976. The new series of
pictures shows both of the Viking landers, never seen from orbit
before, as well as their nearby heat shields and backshells (the tops
and bottoms of the capsules in which they passed through the Martian
atmosphere to land).

The MRO has also found the Mars rover Spirit, the pyramid-shaped
structure in which it landed, its backshell and parachute. The
satellite had already found the rover Opportunity and its landing
structure, sending back images within its first week of operations in
2006 October. The biggest surprise is that what appears to be the
parachute of a Viking lander can still be seen after 30 years. Such
observations could help scientists determine the rate at which dust
accumulates on the surface. The complete series of MRO images will
help future Mars landings avoid potentially dangerous rocky outcrops.
The Phoenix mission, scheduled for 2007, will be the first to benefit
from the new topographical information. Ironically, the MRO images
show the area where Viking 2 came down to be so rocky that "they
wouldn't let us land there now". The new images of Spirit are already
being put to use by its team to plan that rover's next movements.


FORMATION OF GALAXIES
ESO

A team of French and Italian astronomers has shown that galaxies'
environments exert an influence on the way the galaxies form and
evolve. In a three-year survey carried out with the VLT, the
astronomers studied more than 6,500 galaxies over a wide range of
distances, to investigate how their properties vary over different
time-scales, in different environments and for varying galaxy
luminosities. The principal result of the new census is that the
colour-density relation, that describes the relationship between the
properties of a galaxy and its environment, has changed markedly in
the last 7 billion years. Today, galaxies can be roughly classified
as red, where few or no new stars are being born, or blue, where star
formation is still ongoing. Moreover, a strong correlation exists
between a galaxy's colour and the environment in which it resides:
galaxies in dense clusters are more likely to be red than the more
isolated ones.

By looking at a wide range of galaxies of a variety of ages, the
astronomers tried to study how that correlation has evolved over time.
The findings suggest for example that being located in a cluster
quenches a galaxy's ability to form stars more quickly compared with
those in isolation. Luminous galaxies also run out of star-forming
material at an earlier time than fainter ones. The team concludes
that the connection between galaxies' colour, luminosity and local
environment is not merely a result of primordial conditions
'imprinted' during their formation, but that galaxies' relationships
and interactions can have profound impacts on their evolution.


SPA MERCHANDISE

The SPA has a brilliant range of merchandise.

Many items make ideal astro Christmas presents - Laser Pointer Pen,
Astro Diary, Space Musik DVD with images by David A Hardy,
Hubble Image Collection CD-Rom, to name but a few. There is also
a fantastic range of leisurewear including an Outdoor Fleece and a
Thinsulate Beanie Hat - ideal for winter observing. We have a wide
range of astro books including the Patrick Moore 2007 Yearbook of
Astronomy. Go to the SPA website at www.popastro.com to see
the whole range available.


Bulletin compiled by Clive Down

(c) 2006 the Society for Popular Astronomy


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