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 Post subject: ENB No. 199 June 25 2006
PostPosted: Sun Jun 25, 2006 10:11 am 
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Electronic News Bulletin No. 199 2006 June 25

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

Peter Grego

The 2006 July issue of Luna, the journal of the SPA Lunar Section, is
hot off the e-press and packed with 28 pages of Moon material. It is
available as a free download as PDF file (1.28 Mb) from:

By Alastair McBeath, SPA Meteor Section Director

Further to last time's generally negative preliminary visual results
from late
May and early June concerning any potential meteors from dust trails
down by Comet 73P/Schwassmann-Wachmann 3 (SW3) in the past,
some fresh radio and video meteor data are now available.

A preliminary review of the late May radio results from Radio Meteor
Observation Bulletin 154 (May 2006; website:
showed no obvious signs of unexpected activity during the last week.
However, many of the observers were already experiencing problems due
to the, largely summertime, interference by Sporadic-E on some days by
then. A more detailed review will be necessary to confirm this, and to
check for any lesser activity beyond what is normally found at this time
year, but the very weak (to nonexistent) visual rates may not show up
clearly enough in the radio data anyway.

An initial report based on the global video data submitted to Sirko
the International Meteor Organization's (IMO's) Video Commission
Director (circulated on IMO-News on June 15 - see:
suggested just 13 possible SW3 meteors out of a total of 203 meteors
had been caught on video between May 27 and June 1. Sirko described
this level of activity as only marginally detectable, given that, as
last time, a percentage of sporadic meteors will always seem to align
any given radiant area by-chance. Combined with the earlier visual news,
the overall picture remains a predominantly negative one for SW3
meteors in 2006.

Any unsubmitted meteor observations from late May to early June, or
indeed at any other times, would be welcomed by the SPA. Notes on
what to send, and where to, can be found via: .

By Alastair McBeath, SPA Meteor Section Director

Two follow-up pieces to the initial report of a possibly substantial
meteorite fall in north Norway (discussed in the previous ENB), at: and: have
apologetically revised the size of the potentially fallen object
downwards, from 90+ kg to only ~12 kg. The initial comments about it
thus seem to have been rather exaggerated. Despite an entirely
unconvincing photo on the first of the above webpages, supposedly
showing the scar left by the impact, no actual meteorites have been
reported as associated with the event as yet. The "impact scar" was most
likely just an ordinary, fairly recent, rockslide, unconnected to the

The slight controversy about this object was as nothing to the heated
debate which has broken out regarding the postulated Permian-Triassic
boundary crater, reported as discovered below the ice of Wilkes Land,
Antarctica, also in ENB 198. Several experts have questioned not only
whether it really lies in rocks of the right age, but even whether the
detected gravity anomaly is due to an impact crater at all. Very
sub-ice ground investigations will be necessary to determine details of
what it really is, till when the debate will no doubt continue.
on the topic, and the debates surrounding it, pro and con, can be traced
on the Internet from the SPA's General Chat Forum, "Permian grand
slam" topic at: .

By Alastair McBeath, SPA Meteor Section Director

While all of the above was underway, NASA was busy finalising an
analysis of their latest Earth-detected lunar impact flash, which
on 2006 May 2. The flash lasted about 0.4 sec. NASA researchers
estimate the impactor as being about 25cm in size, travelling at 38
and that it created a crater around 14m in diameter by 3m deep, much
too small to be seen from Earth. The object struck Mare Nubium, in the
south-west quadrant of the Moon's visible disc, just north-east of the
brightest rays from the crater Tycho which cross that Mare, roughly
halfway between the crater Bullialdus and the Mare's southern edge down
the line of the ray. A slow-motion replay of the impact flash, with
details, including a light-curve for the event, can be seen at: .

By Alastair McBeath, SPA Meteor Section Director

As part of the ongoing improvements to the SPA website, a new page
should be going online by this weekend, with links to topics on various
the SPA's electronic Forums that have had particular usefulness and
relevance for those interested in meteors, including a special list of
such items posted. It can be accessed from the meteor homepage.

By Alastair McBeath, SPA Meteor Section Director

This year's International Meteor Conference (IMC) takes place at
Roden in The Netherlands from September 14-17 inclusive, and as usual
it will bring together amateur and professional meteor enthusiasts from
around the world. IMCs are always great fun for anyone with a real
interest in meteors. There is a daily programme of lectures and poster
presentations, dealing with all branches of meteor astronomy, plus an
excursion will be mounted to visit the LOFAR telescope, which will be
the largest telescope in the world when it's finished. Despite all this
planned activity, there is always ample time to talk to the many
with similar interests. As the Conference's official language is
English, this
could scarcely be easier for anyone from the UK wishing to attend.

Although the IMC is the IMO's main annual meeting, and includes the
IMO's General Assembly, you do not need to be an IMO member to
register for, or attend, the IMC. At present, you can still apply for
reduced early registration fee of 120 Euros, providing you do so before
July 1. From July 1st onwards, the price increases to 130 Euros. This
price includes accommodation, meals, the excursion, entry to all parts
the IMC, and a copy of the Conference's "Proceedings".

Full information about the IMC, including a registration form, is
at: .

This year, the IMC organizers have arranged two additional meteor
schools, to run from September 11-13 inclusive, and also in Roden: a
Radio Meteor School, and a Meteor Orbit Workshop. The costs to
attend either will be 120 Euros in addition to the cost of the IMC. If
wish to attend one of these, you MUST contact the organizers BEFORE
July 1st. However, be warned, as these are NOT courses for beginners,
and assume near-graduate level knowledge of both physics and
mathematics. As both courses run simultaneously, it would be possible to
only attend one. Again, more information is available at the above IMO
website address.


A tiny asteroid that has appeared to loop around the Earth for the
past seven years is about to leave the neighbourhood. 2003 YN107
arrived in 1999 and has been following a corkscrew path round the
Earth ever since. The 20-metre object belongs to a population of
Earth 'co-orbital asteroids'. Essentially, they have orbits quite
similar to the Earth's, going around the Sun in almost exactly one
year. Occasionally a co-orbital catches up the Earth from behind, or
vice versa, and the asteroid, while still orbiting the Sun, slowly
corkscrews around our planet. Such asteroids are not truly captured
by the Earth's gravity, but for a time they give that impression from
our point of view.

At least four small asteroids are known to be co-orbital -- 2003
YN107, 2002 AA29, 2004 GU9 and 2001 GO2, and the list may grow as
asteroid surveys improve in sky coverage and sensitivity. At the
moment, only two co-orbitals are actually nearby, 2003 YN107 and 2004
GU9; the others are scattered around the Earth's orbit. 2004 GU9 is
perhaps the most interesting. It measures about 200 metres across,
relatively large, and new calculations show that it has been looping
around the Earth for 500 years and will continue doing so for another
500 before the present episode comes to an end.

Earlier this month, 2003 YN107 came to within 3.4 million km of the
Earth, slightly closer than usual. That allowed the Earth's gravity to
give the asteroid the nudge it needed to leave. In about 60 years
2003 YN107 will lap Earth again, resuming its role as a temporary
moonlet. In due course, other co-orbitals will do the same.

The Register

A computer model developed by scientists at the Southwest Research
Institute in Boulder, Colorado, may shed new light on the formation of
many of the moons in the Solar System. It has long been clear that,
collectively, the moons of Jupiter, Saturn and Uranus amount to a
similar proportion of their parent planet's mass -- around 0.01 per
cent. What has not been clear is why that should be, or why the moons
are the sizes that they are, or distributed in the orbits that they
inhabit. Existing models also fail to account for why some of the
moons contain ice, as they suggest that the moons formed too quickly
(and therefore at too high a temperature) to acquire a watery
component. The new model produces gas giants with moon sizes and
distributions consistent with real-world examples and also explains
the apparent upper limit on the masses of the moons.

The model proposes that, in the final stages of its formation, a
gas-giant planet accretes both gases and solids from a disc of such
debris orbiting the Sun. That material then forms, in the equatorial
plane around the planet, its own disc which in turn give rise to
satellites. According to the model, as the satellites grow they
induce spiral waves in the gas disc. The interactions between the
waves and the proto-moons cause the orbits to contract. The orbits of
the more massive satellites contract more quickly, and collapse into
the planet itself, while the orbits of the smaller moons stabilise.
The researchers also suggest that there are many cycles of moon
formation and loss, so the moons that we see today are merely the last
ones to form. Uranus, however, remains something of a mystery. The
researchers believe that the key to understanding it must be in how it
came to be lying on its side; only then will they know whether their
new model may apply.

Carnegie Institution

Three new objects locked into the same orbit as Neptune -- called
'Trojan' asteroids -- have been found by users of the Gemini telescope
in Hawaii. The discovery brings the total of known Neptune Trojans to
four. There may well be a lot more, but they are hard to observe
because they are so far away from the Sun.

Discovery News

Two tiny moons which were discovered last year to orbit Pluto at
distances of about 49,000 and 65,000 kilometres have been officially
named by the International Astronomical Union (IAU) as Nix and Hydra,
respectively, after characters from Greek and Roman mythology. Nix
was originally spelt Nyx after the goddess of the night and mother of
Charon, but the IAU changed the spelling to Nix to avoid confusion
with an asteroid already named Nyx; Hydra is a mythological nine-
headed beast that guards the entrance to Pluto's realm. In addition
to their mythological etymologies, the names Nix and Hydra have an
oblique modern significance -- their initials are a nod to New
Horizons, the name of the spacecraft now on its way to Pluto.


Astronomers say they have found a comet-like ball of gas, that may be
about a megaparsec (three million light-years) long and over a billion
times the solar mass, ploughing into a distant galaxy cluster. It is
much the largest object of its kind ever identified. It emits X-rays
but not visible light, though it contains visible galaxies. It is in
a cluster of galaxies called Abell 3266, a massive agglomeration that
contains hundreds of galaxies and hot gas and is itself part of a
supercluster called Horologium-Reticulum. The astronomers have said
that the object appears from Earth as a circular glow of X-radiation
with a comet-like tail nearly half the size of the Moon. The gas ball
is at 46 million degrees C, but that is only a measure of the rates at
which the atoms of the gas are moving -- the material is so sparse
that if one could put a thermometer in it the mercury would freeze
just as it would in the vast majority of places in the Universe.

New Scientist

An unusual object has been observed by a team using the Hubble Space
Telescope to look for very distant supernovae. At first glance, the
object discovered on February 22 in the constellation Bootes resembled
an ordinary supernova, but it kept growing brighter for much too long,
taking at least 100 days to reach peak brightness whereas normal
supernovae peak after about 20 days. There had been nothing visible
at its position on January 29. The object's colour has not altered
since it was first observed; normally, temperature changes after an
explosion cause colour changes. The spectrum is also unusual, to the
point where the identities of features in it are uncertain. If the
strongest feature is interpreted as the calcium H and K lines, the
red-shift would be 0.54, corresponding to a distance of 5.5 billion
light-years, but the object is too bright to be a supernova at that
distance, and there is no sign of a host galaxy, which should be
visible. At the moment, therefore, astronomers can only speculate on
what the object is. The best hope to resolve the question is
obviously to make more observations, in the hope that the spectrum
will evolve and show some features that can be recognized; another
Hubble observation is scheduled for June 25.

Bulletin compiled by Clive Down

(c) 2006 the Society for Popular Astronomy

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