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 Post subject: ENB No. 174 May 9 2005
PostPosted: Sat Dec 03, 2005 8:50 am 
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The SOCIETY for POPULAR ASTRONOMY
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Electronic News Bulletin No. 174 2005 May 9
====================================================


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/maaduPuabgNtQciD1pRb/

Philip's, a publisher of astronomy books and planispheres for the
amateur astronomer, is sponsoring this bulletin. For information on
certain Philip's titles and offers see below.


MOONLIT LYRIDS STILL A PLEASURE
By Alastair McBeath, SPA Meteor Section Director

As noted in ENB 172, the Lyrid maximum on April 22 was expected
during UK daylight hours, and had a bright waxing gibbous Moon. The
weather was unhelpful for many British watchers, and no visual Lyrid
sightings have come in from here as yet. However, Steve Evans in
Gloucestershire had some better skies on April 21-22, and recorded 22
meteors (11 Lyrids) in 7.5 hours of automated video recording. Details
as to what happened elsewhere too are still sketchy, but some European
observers in Germany and the Netherlands, including the International
Meteor Organization's President Juergen Rendtel in northern Germany,
enjoyed some very pleasing Lyrid meteors on April 21-22, through till
dawn twilight. Juergen's best Lyrid was a magnitude -5 event with a
persistent train lasting more than 20 seconds. The shower is noted for
occasionally producing very bright meteors, certainly. Observed Lyrid
rates in these reports were up to 6 or 7 an hour, yielding Zenithal Hourly
Rates around 14 +/- 5, perhaps still several hours before the peak.

All additional Lyrid data would be welcomed by the SPA Meteor
Section. Details on what to report and where to can be found off the
Section's homepage at: http://popastro.c.topica.com/maaduPuabgNtRciD1pRb/


BAA COMET SECTION MEETING
By Jonathan Shanklin

All SPA members are welcome to come along to the BAA Comet
Section meeting next Saturday (May 14) at the Institute of Astronomy,
Cambridge. Details are on my web page at
http://popastro.c.topica.com/maaduPuabgNtSciD1pRb/


EXTRA-SOLAR PLANETS' ECCENTRIC ORBITS
Northwestern University

Most of the more than 160 extra-solar planets detected in the last
decade have eccentric orbits. The Upsilon Andromedae system is a case
in point. It consists of the central star and three Jupiter-like
planets. The inner planet, a 'hot Jupiter' so close to the star that
its orbital period is only a few days, was discovered in 1996; the
two outer planets, with elongated orbits that perturb one another
strongly, were discovered in 1999.

A group of astrophysicists that has been studying that system claims
that a simple mechanism that it calls 'planet-planet scattering',
arising from the increased gravitational attraction between two
planets when they come very near to one another, must be responsible
for the highly eccentric orbits observed in the Upsilon Andromedae
system. The group believes that such scattering must have occurred
frequently in extra-solar planetary systems, not just that one. So
while planetary systems around other stars may be common, the kinds of
systems that could support life, which, like our Solar System,
presumably must remain stable over very long time-scales, may not be
so common. In the particular case of Upsilon Andromedae the research
group has proposed that the present situation may have arisen through
interaction between the outermost of the three planets and a
hypothetical fourth planet that has since been ejected from the system.


VARIABLE OBJECT IN BOOTES
IAU

A 0.5-m automated supernova-patrol telescope has discovered a 16th-
magnitude variable object in Bootes, 37" west and 184" north of the
centre of the galaxy IC 4516. The object had not been detected during
previous searches of that area. The object appears to be identifiable
with the radio source 3C 306 (possibly a quasar).


POSSIBLE EXTRA-SOLAR ASTEROID BELT
AP

Astronomers using the Spitzer Space Telescope have detected a ring of
warm dust around the star HD 69830, one of 85 Sun-like stars that they
observed. They suggest that the dust implies the existence of a belt
of asteroids, whose mutual collisions would produce the observed dust.
The belt seen in HD 69830 is thicker than the asteroid belt in the
Solar System and is nearer to the central star. More observations are
needed to confirm that the dust has come from asteroid collisions and
to rule out an object like a comet. Two analogous belts have
previously been found, but they are around younger, denser stars.


HOT SPOTS ON NEUTRON STARS
The Register

European astronomers have seen, for the first time, azimuthal
variations of temperature on the rotating surfaces of three
(relatively) nearby neutron stars -- the incredibly hot and dense
remnants of supernova explosions. The measurements, made with the
XMM-Newton space telescope, map surface features ranging from 1 to 3
kilometres across on bodies hundreds, even thousands of light-years
away. The astronomers measured the apparent temperatures of the stars
at ten equally spaced rotational phases. Variations were seen.
Scientists had foreseen the existence of hot spots -- regions where
the electromagnetic energy emitted by the star is funnelled back down
to the surface and heats a local area above the temperature of its
surroundings. The research team suspects that the hot spots are
linked to polar regions, and are somewhat analogous to the aurorae on
planets with magnetic fields.


CASSINI FINDS ORGANIC MATTER ON SATURN'S MOON TITAN
AP

Cassini flew within 638 miles of Titan's frozen surface on April 16
and discovered a hydrocarbon-laced upper atmosphere. Titan's
atmosphere is mainly made up of nitrogen and methane, the simplest
hydrocarbon. Scientists were surprised to find complex organic
material high in the atmosphere, because Titan is so cold that the
material could be expected to condense and rain down to the surface.


RADIO TELESCOPE INCLUDES SUPERCOMPUTER
New Scientist

One of the world's most powerful supercomputers is to be the brain of
a new radio telescope called LOFAR. The telescope will look back to
the time of the very first stars, map our Galaxy's magnetic field and
perhaps identify the sources of high-energy cosmic rays. Instead of
one large rigid dish, LOFAR will use thousands of simple radio
antennae. Their signals will be combined at the University of
Groningen in the Netherlands by STELLA, the new supercomputer, which
is unofficially ranked as the third-most-powerful on the planet.

LOFAR needs its own supercomputer because it aims to detect radio
wavelengths of up to 30 metres. Such long-wave radio images are
blurry, and the only way to make them sharper is to build a vast array
of detectors spread over hundreds of kilometres. Unfortunately, a
layer of the Earth's upper atmosphere called the ionosphere bends such
radio waves unpredictably -- it makes any cosmic radio source twinkle
-- and with receivers scattered over a wide area the twinkling is
disastrous, washing out the image completely. The solution is to use
some of the radio data to monitor the ionosphere, modelling its
fluctuations with STELLA, and compensate for the twinkling effect.
That has to be done in real time, which needs STELLA's huge computing
power.


NEAR-PERFECT EINSTEIN RING FOUND
ESO

Astronomers using the Very Large Telescope in Chile have reported the
discovery of a three-quarters-complete Einstein ring. The most
complete previously discovered one -- which is also one of the few
visible in optical light -- is slightly less than a half-circle in
circumference (170 degrees). The newly discovered one is C-shaped,
extending 270 degrees, and has a radius of slightly more than 1 3/4
arc seconds. The lens is a giant elliptical galaxy similar to M87,
and lies some 7 billion light-years away in the direction of the
constellation Fornax. The source galaxy has a red-shift of 3.77,
suggesting a distance of roughly 11 billion light-years. The
significance of this find is that the source amplified by the lens is
the galaxy with the brightest apparent luminosity ever discovered at
such a distance. It may provide information on the physical conditions
prevailing in the interstellar medium when the Universe was only 12%
of its present age. The shape of the source is also important because
it gives the amount of mass within the lens at a redshift of z=1; only
a handful of Einstein rings has been discovered at such high redshift.


'WONDERFUL' STAR REVEALS ITS HOT NATURE
Chandra X-Ray Center

One of the stars earliest recognised as variable is Omicron Ceti,
named Mira (meaning 'the wonderful'). Judged purely by its
variability, it is an ordinary long-period variable (a highly evolved
red giant star pulsating in a period of about a year). Mira is,
however, a binary system in which the long-period variable is paired
with another object that is probably a white dwarf. The Chandra
satellite's ability to distinguish between the two interacting stars
allowed a team of scientists to observe an X-ray outburst from the
giant. Previously it was assumed that all the X-rays came from a
hot disc surrounding the white dwarf, so the detection of an X-ray
outburst from the giant star came as a surprise. The Mira system is
about 420 light-years from Earth, and the two stars are about 6.5
billion miles apart, or almost twice the distance of Pluto from the
Sun. The activity in the red giant Mira A could create magnetic
disturbances in the upper atmosphere of the star and lead to the
observed X-ray outbursts, as well as the rapid loss of material from
the star in a strong stellar wind. Some of the material in the wind
from Mira A is captured in an accretion disc around Mira B, where
collisions between rapidly moving particles produce X-rays. An
intriguing aspect of the observations of Mira at both X-ray and
ultraviolet wavelengths is the evidence for a faint bridge of material
joining the two stars. The existence of a bridge would indicate that,
in addition to providing material from the stellar wind, Mira A is
also spilling material directly into the accretion disc round Mira B.


TWELVE NEW MOONS FOR SATURN
BBC News

Astronomers have discovered 12 new moons orbiting Saturn. The moons
are small, irregular bodies -- probably only about 3 to 7 km in size
-- that are far from Saturn and have orbital periods ranging from 820
to 1354 days. All but one circle Saturn in the opposite direction to
its larger moons, a characteristic of captured bodies. Jupiter is the
planet with the most moons, 63 at the last count. Saturn now has 46,
Uranus 27 and Neptune 13. The latest ones were found last year with
the Subaru telescope in Hawaii. Confirmatory observations were made
last month with the Gemini North telescope also situated in Hawaii.
The newly-found satellites were probably formed in the main asteroid
belt between Mars and Jupiter, and scattered out of it by Jupiter's
gravity. The key question is how they came to be captured by Saturn.
The current models devised to explain how such bodies are captured
are unable to explain how they could have reached the orbits they now
possess.



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Bulletin compiled by Clive Down

(c) 2005 the Society for Popular Astronomy


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