ENB No. 204 September 17 2006

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ENB No. 204 September 17 2006

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Electronic News Bulletin No. 204 2006 September 17

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://popastro.c.topica.com/maafavSabtmXQciD1pRb/

By Alastair McBeath, SPA Meteor Section Director

The suggested ionization train lasting for at least three minutes
around 02:06 UT on August 27-28 (reported in ENB 203), which
if so would likely have resulted from a bright fireball, has turned out
to be non-meteoric unfortunately. Instead, a new source of light
pollution has manifested, with a freshly-installed sensor-activated
so-called "security" light illuminating a short stretch of telephone
wire for a few minutes. Something more to be aware of for
observers of such chance phenomena.

By contrast, seven sightings of the August 28-29, circa 21:05 UT
fireball, have now arrived, the fresh observations since the last
ENB made from Middlesex, Suffolk and a second witness in
Staffs. Investigations to try to refine the possible projected surface
track suggested previously remain on-going.

Meanwhile, three UK fireball events have been spotted from early
September: Sep 1-2, ~23:35 UT, mag -6/-9(?) from Northumberland;
Sep 3-4, ~23:40 UT, very bright, from Staffordshire (the place to be
for fireball sightings in recent weeks it would seem!); and Sep 7-8,
20:02 UT, a bright fireball from NE England.

More sightings of these or any other fireballs are welcomed by the
Section, particularly those seen from the UK and places nearby.
Details of what information to send and where to can be found via
the Section's "Fireball Observing" page at:

http://popastro.c.topica.com/maafavSabtmXRciD1pRb/ .


A small flash was detected on the Moon as the SMART-1 spacecraft
crashed into it on the night of September 2. The impact took place
in an area of the Moon in the vicinity of Lacus Excellentiae,
unilluminated by the Sun but near the terminator, at a grazing angle
of between 5 and 10 degrees and a speed of about 2 kilometres per
second. The planned impact concluded a successful mission that, in
addition to testing innovative space technology, had been conducting a
thorough scientific exploration of the Moon for about a year and a

New Scientist

Future satellites could use X-ray-emitting stars, rather than GPS
signals, to get their bearings, according to plans by the US military.
X-ray navigation technology would be less vulnerable to enemy
interference than GPS, and could also be used far from Earth to help
interplanetary space probes keep track of their positions. The X-ray
beacons would be pulsars, rapidly spinning stars which emit regular
pulses of X-rays as they spin. Each pulsar has a unique frequency and
location in the sky. Locking onto any one of them would tell the
satellite which direction is which in the sky. The signals from
several pulsars could be exploited to determine a spacecraft's
position and velocity in the same way as by GPS, but in principle it
would be simpler because the beacons are fixed. The pulsar signals
are ideal for the purpose, because their frequency stability rivals
that of atomic clocks. A further useful feature of the system, from a
military point of view, is that X-ray detectors are not easily blinded
by lasers which might be aimed at them maliciously, nor by being
pointed accidentally at the Sun, unlike the visible-light cameras used
to track ordinary stars.

Science Daily

The apparent absence of shadows where shadows were expected to be is
raising a question about the faint glow of microwave radiation that
has been regarded as proof that the Universe was created by a 'Big
Bang'. In a finding sure to cause controversy, scientists at the
University of Alabama found a lack of evidence of shadows from
'nearby' clusters of galaxies in new, highly accurate measurements of
the cosmic microwave background. A team of scientists used data from
the Wilkinson Microwave Anisotropy Probe to scan the microwave
background for shadows caused by clusters of galaxies.

If the background really originated in the Big Bang fireball, then it
should appear to come from further away than anything else that is
observable, and massive clusters of galaxies should all cast shadows
on the background. The principle of shadowing is elementary: if you
see a shadow from a cluster, it means that the radiation comes from
behind it, but if you don't see a shadow, then you have something of a
problem. Among the 31 clusters that were studied by the team, some
appear to show a shadow effect and others do not. Taken together, the
data show a shadow effect about one-quarter of what was predicted --
an amount roughly equal to natural variations previously seen in the
microwave background across the entire sky.


The Mars rover Opportunity is closing in on what could be the richest
scientific findings of its mission so far. Within the next week the
robotic geologist is likely to reach the rim of a crater bigger than
any it has previously visited. The crater, known as Victoria, is
approximately 750 m in diameter and 70 m deep. Images from the Mars
Global Surveyor orbiter show the crater walls to expose a stack of
rock layers approximately 30 to 40 metres thick. Opportunity will
send back its initial view into the crater as soon as it gets to the
rim, and its controllers hope to use its observations from various
points around the rim to try to plot a route for it to enter the

The twin rovers have been exploring landscapes on opposite sides of
Mars since 2003 January. Originally, their missions were supposed to
last three months, but both are still investigating Mars' rocks, soils
and atmosphere after more than ten times as long. Opportunity works
in a region where rock layers hundreds of metres in thickness cover
older, heavily cratered terrain.


Astronomers using the Hubble telescope have photographed one of the
smallest objects ever seen around a normal star beyond our Sun. With
12 times the mass of Jupiter, the object, CHXR 73 B, is small enough
to be a planet, but it is also massive enough to be a brown dwarf, a
failed star. There is at present no consensus on how to decide which
objects orbiting other stars are truly planets. Hubble discovered the
object while conducting a survey of isolated brown dwarfs. CHXR 73 B
is 19.5 billion miles from its red-dwarf primary, roughly 200 times
farther than the Earth is from the Sun. At 2 million years old, the
star is very young when compared with the Sun. Young brown dwarfs are
brighter than older, cooler ones, so they can be seen at lower masses,
where older dwarfs would be undetectable. Hundreds of brown dwarfs
have been found in our Galaxy since the first ones were discovered
about a decade ago. Most of them are alone in space and not orbiting

There is interest in studying young star systems in an effort to
understand how small bodies formed. Planets are supposed to form in
circumstellar discs of dust and gas, but such discs are normally not
big enough to cover the region in which CHXR 73 B is seen; even if the
red-dwarf primary possesses a disc there would not be enough material
at that distance from it to create a planet. Theoretical models show
that giant planets like Jupiter form no more than about 3 billion
miles from their stars.


Pluto has been given a new name to reflect its new status as a dwarf
planet. On September 7, the former 9th planet was assigned the
asteroid number 134340 by the Minor Planet Center. The move gives
expression to the International Astronomical Union's recent decision
to strip Pluto of its planethood and place it in the same category as
other small Solar-System bodies with accurately known orbits. Pluto's
satellites, Charon, Nix and Hydra are considered to be part of the
same system and will not be assigned separate asteroid numbers,
according MPC director emeritus Brian Marsden. Instead, they will be
called 134340 I, II and III, respectively. There are currently
136,563 asteroid objects recognized by the MPC; 2,224 new objects were
added last week, of which Pluto was the first.

The name Xena by which the body formally designated 2003 UB313, whose
size (slightly larger than Pluto's) precipitated the recent concern
over the definition of planets, is another casualty of recent IAU
decisions -- the object has been assigned the asteroid number 136199
and officially named Eris. Eris is the Greek goddess of discord, so
the name hints at the troubled ordination of the newly-discovered
body. One of Eris' discoverers, Michael Brown of the California
Institute of Technology, said that the new name was "too perfect to
resist". Eris' moon has been named Dysnomia, after Eris' daughter --
the spirit of lawlessness -- in Greek mythology. Eris joins Pluto and
Ceres in the new category of 'dwarf planets'.

Bulletin compiled by Clive Down

(c) 2006 the Society for Popular Astronomy

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