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 Post subject: ENB No. 178 July 24 2005
PostPosted: Sat Dec 03, 2005 8:56 am 
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The SOCIETY for POPULAR ASTRONOMY
***********************************
====================================================
Electronic News Bulletin No. 178 2005 July 24
====================================================


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/maadMEkabiUvuciD1pRb/

Philip's, a publisher of astronomy books and planispheres for the
amateur astronomer, is sponsoring this bulletin. There is information
on certain Philip's titles and a special offer at the end.



RECENT METEOR & FIREBALL NEWS
By Alastair McBeath, SPA Meteor Section Director

The full set of June radio results from Radio Meteor Observation Bulletin
143 (see website http://popastro.c.topica.com/maadMEkabiUvvciD1pRb/ has now
arrived, courtesy of
editor Chris Steyaert, and it confirmed that no unusual meteoric activity
was detected around June 12, possibly associated with Comet
P/2005 JQ5 (Catalina) as discussed in ENB 177. A lot of observers
struggled with interference problems all month however, and some found
even the major daylight shower peaks of the Arietids and Zeta Perseids,
due near June 7 and 9 respectively, were largely lost to noise.

Two more significant fireball reports have come through since last time.
One was a bright event spotted by part of a group observing in Ayrshire,
south-west Scotland at 00:20 UT on June 23-24. The second was
around sunset from Britain, at 20:19 UT on July 16-17, record at several
sites in south-east England and Belgium. It was clearly very bright, and
the magnitudes suggested so far - roughly -3 to -8 - may be
underestimates because of the near-daylight sky. Two reports of a strong
radio signal (one British, one Belgian), generally coincident with the visual
sightings, have been used to refine the time of occurrence. Early indications
are the meteor may have passed high above the southern Channel towards
north-west France, but details on this possible track are still sketchy.

Fireball reports - observations of meteors of visual magnitude -3 or
brighter - are always welcomed by the Section. Information on what to
report and where to can be found on the "Fireball Observing" page of the
SPA website, off the Meteor homepage at:
http://popastro.c.topica.com/maadMEkabiUvwciD1pRb/


COMET DEBRIS IS POWDERY
AP

Deep Impact scientists say that the plume of debris that spilled from
Comet Tempel 1 after it collided with a space probe is as fine as
talcum powder, suggesting to them that the comet formed gradually.
Soon after the 820-pound probe hit the comet, they detected evidence
of water, carbon dioxide and organic substances that were released.
The high-speed collision produced two flashes of light and hurled a
plume of fine, powdery dust from the comet thousands of miles into
space. Scientists had been looking forward to seeing how large a
crater was excavated by the impact, but it had not occurred to them
that the parent spacecraft's view of the crater would be masked by the
great cloud of dust that was ejected. Long before the larger-than-
expected debris cloud dissipated, the spacecraft was no longer in a
position to view the impact site and in any case the craft was soon
too far away to be able to resolve it even if it had been unobscured.


POSSIBLE NEW MISSION FOR DEEP IMPACT SPACECRAFT
Space.com

Astronomers are hoping to obtain funds to allow the Deep Impact parent
spacecraft to visit Comet 85P/Boethin in late 2008. That comet made
two close approaches to Jupiter during the 20th century and will make
two close approaches to Earth and two to Jupiter during the first half
of this century. There seem to be major differences between the
nuclei of the comets that have been observed from close quarters by
spacecraft (Halley, Borrelly, Wild 2 and Tempel 1). Tempel 1 does not
conform to the 'fresh surface -- no impact craters -- crusted-over
dirty iceball model that was popular previously, so the more cometary
nuclei that can be studied at high resolution the better. Comet
Boethin is one of the most accessible periodic comets for the Deep
Impact spacecraft and would require the shortest flight time. A
concern about Boethin is that it has been seen only in 1975 and
1986. It was missed at its 1997 return to the Sun because it was on
the far side of the Sun from the Earth. The spacecraft team would be
reassured if a large telescope could recover the comet this year or
next, in good time before its return to perihelion in 2008.


TIME ADJUSTMENT AT YEAR'S END
IAU

A positive leap second will be introduced at midnight on 2005 December 31.


PLANET HAS THREE SUNS
Caltech

An extra-solar planet has been discovered in HD 188753, a three-star
system about 150 light-years away in Cygnus, by a Caltech scientist
using the 10-m Keck I telescope. The planet is slightly more massive
than Jupiter and is orbiting one of the three stars that constitute
the system. About as far away from the planet's star as Saturn is
from the Sun is a companion object that is itself composed of two
stars, as was discovered about 30 years ago by the astronomer who
usually vets these Bulletins; the separation of the close pair is
comparable with that between the Earth and the Sun. Most of the
extra-solar planets have been discovered so far by use of a precise
velocity technique (developed in part by the same astronomer) that is
easier to employ in studies of single stars. Binary and multiple
systems have usually been avoided, partly because theories have
suggested that planets were unlikely to be able to form in such
environments.


BIGGEST EVER COSMOS SIMULATION
BBC Online

Astronomers have used supercomputers to try to model how the Universe
evolved into the shape it is today. The simulation is more detailed
than has been attempted previously, and shows structures in the
Universe changing and growing over billions of years. The
international team of scientists known as the Virgo Consortium looked
at how the Universe evolved under the influence of the invisible
material called dark matter. According to cosmological theory, soon
after the Big Bang cold dark matter formed the first large
structures, which then collapsed under their own gravitation to form
vast haloes. The gravitational attraction of the haloes brought in
normal matter, providing a focus for the formation of galaxies. The
simulation tracked some 10 billion dark-matter particles over roughly
13 billion years of cosmic evolution. It incorporated data from
satellite observations of the heat left over from the Big Bang,
information on the make-up of the Universe and current understanding
of the laws of physics on Earth. The Astronomer Royal, Professor Sir
Martin Rees, said "Now we have the simulations, we have the
predictions of the theory in enough detail that we can see if there is
a meshing together of how the world looks on the larger scale and the
way we expect it should look according to our theories. It's a way to
check our theories."

Comparisons between the results of the simulation and actual
observations are already helping to shed light on some unsolved
problems. Some astronomers have previously questioned how radio
sources in quasars could have formed so quickly after the Big Bang
under the cold-dark-matter model. The simulation suggests that such
structures form naturally in numbers consistent with data from the
Sloan Digital Sky Survey.


RARE TYPE OF NEUTRON STAR
ESA

An international team of scientists has discovered a new example of a
rare type of neutron star. It has been called IGR J16283-4838 and is
about 20,000 light-years away, deep inside the spiral arm of Norma in
our Milky Way galaxy, obscured by dust, and then buried in a binary
star system enshrouded by dense gas.

There are many neutron stars embedded in the Galaxy's spiral arms, but
the problem is that those arms are too dusty to see through in visible
light. The scientists who first found the IGR object with the gamma-
ray satellite Integral could not immediately decipher its nature, so
they enlisted the help of the Rossi X-ray Timing Explorer and the
newly launched Swift satellite to observe it in different wavelengths.
Because gamma-rays are hard to focus into sharp images, the scientific
team used the X-ray telescope on Swift to determine a precise
location. In mid-April Swift confirmed that the light was 'highly
absorbed', meaning that the binary system is filled with dense gas
from the stellar wind of the companion star. Later the Rossi Explorer
observed the source, which was then fading away. That observation
revealed a familiar light signature indicating a fading high-mass
X-ray binary with a neutron star.

IGR J16283-4838 is the seventh so-called 'highly absorbed', or hidden,
neutron star to be identified. The numbers of neutron stars, which
are created from fast-burning massive stars, are intrinsically tied to
star-formation rates. They are also energetic 'beacons' in regions
too dusty to study in detail otherwise. As more and more are
discovered, new insights about what is happening in the Galaxy's
spiral arms may emerge. IGR J16283-4838 revealed itself with an
'outburst' on or near its surface. Such stars are often part of
binary systems, in orbit with a normal star. Occasionally, gas
originating from the normal star crashes onto the surface of the
neutron star and releases a great amount of energy. The outbursts can
last for weeks before the system returns to dormancy for months or
years.


CHARON OCCULTS STAR
The Register

On July 11, astronomers observed Pluto's moon, Charon, occult a star.
Such an event has been observed only once before, 25 years ago, and
then with a single telescope. This time, the researchers trained four
telescopes in Chile on the occultation, to capture as much detail as
possible including a measure of the roundness of the moon, and its
radius. The data could also reveal whether or not the moon has an
atmosphere. Although Charon is very small, and would not have much
gravity to hold on to an atmosphere, it is so far from the Sun and so
cold that the researchers speculated that some gases could yet be
retained. The results of the observations are not yet public
knowledge.



PHILIP'S NEW TITLES AND SPECIAL OFFER

Special Offer! £10 off the retail price of £30 and free p&p when you
purchase your copy of Atlas of the Universe by Sir Patrick Moore, the
definitive guide to the stars, planets and the Universe by Britain's
best-known astronomer. To order call 01903 828 503 quoting Philip's
52. Offer ends July 29.

NEW EDITION! PHILIP'S GUIDE TO THE NIGHT SKY (48-page paperback,
£4.99, ISBN 0540087017). SIR PATRICK MOORE takes the novice
astronomer on a guided tour of the stars and constellations of the
northern hemisphere. An accessible work, clearly and concisely
written.



Bulletin compiled by Clive Down

(c) 2005 the Society for Popular Astronomy


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