ENB No. 181 September 4 2005

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ENB No. 181 September 4 2005

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Electronic News Bulletin No. 181 2005 September 4

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/maadWviabj1F2ciD1pRb/

Philip's, a publisher of astronomy books and planispheres for amateur
astronomers, is sponsoring this bulletin. For information on a
Philip's publication see the end of this bulletin.

By Alastair McBeath, SPA Meteor Section Director

Further to the notes last time, more complete datasets from across the
Perseid maximum have now reached the Section, and it is clear from
those that southern England was THE place to be in the UK for Perseid
observing this summer. Several observers there were able to observe on
five to seven consecutive nights, including the essential August 12-13, a
most unusual, excellent run. From the Midlands north however, there was
commonly a lot of cloud or haze during these nights, and consequently
much less meteor watching was possible. Scotland and Wales seem to
have done notably badly, with no positive reports in as yet from either for
August 12-13, for instance. Overall however, British observations are
available to the Section from every night between August 6-7 to 17-18
inclusive, giving a useful view right through the Perseids' best.

The predicted maximum interval, around 17:00-19:30 UT on August 12,
was not covered by observers reporting to us so far, and there was an
unfortunately-timed gap in data from 15:20-20:20 UT then in the
International Meteor Organization's preliminary report (issued on the
IMO-News e-mailing list on August 25; see website:
Thus we cannot be sure when the real peak may have occurred. The
early IMO results suggested rather a broad maximum, with Zenithal
Hourly Rates (ZHRs) around 70-90 present for most of August 12
through to around 03:00 UT on August 13. A close inspection of the
results suggests the marginally better activity after 20:20 UT on August
12-13 may have been from roughly 23:00 UT to 00:30 UT, when ZHRs
were 80-90, but this needs confirming.

In the SPA analysis, the possible peak around 23:15 UT +/- 1.25 hours
on August 12-13, mentioned in ENB 180, now looks less pronounced,
thanks to more better-sky results being available. Even so, the mean
ZHRs from 20:00 to 00:00 UT that night seemed consistently higher at
~90-110, than between 00:00 to 02:30 UT (~70-90), and had clearly
fallen well back, to around 40-60, by the time night had fallen again over
the USA on August 13. The better North American rates were seen the
previous night (August 11-12), with ZHRs ~70-90. The information so
far would not be inconsistent with a true maximum between 17:00-19:30
UT on August 12 at least, though not proving it.

People who provided details from their Perseid observing (whether
successful or less so) this August, directly and via the SPA Forum,
included: Jay Brausch (North Dakota, USA), Mike Dale (Edinburgh),
Clive Down (Cardiff), Mike Feist (Sussex), Dave Gavine (Edinburgh),
Shelagh Godwin (SW France), Alan Heath (Nottingham), Zoltan Hevesi
(Hungary), Robin Leadbeater (Cumbria), Ian Lee (Cumbria), Robert
Lunsford (California, USA), Tony Markham (Staffordshire), Tom
McEwan (Ayrshire), Ian Ransom (Hampshire), Robin Scagell
(Oxfordshire), Jonathan Shanklin (Cambridgeshire), Mark Smith
(Lincolnshire), George Spalding (Oxfordshire), Enrico Stomeo (Italy),
Richard Taibi (Maryland, USA), Mark Vints (Belgium), Chris
Woodcock (East Sussex), Robert Wright & his son (Cornwall), and the
Director (Northumberland), plus another ten SPA Forum correspondents
who did not give their full names, or occasionally even their observing
locations. Grateful thanks go to one and all for providing the information
to allow such a very swift, and detailed, preliminary analysis.

More data is always welcome however, and if you have results still to
submit, please send them in as soon as possible! Information on what to
report and where to can be found off the SPA Meteor homepage at:
http://popastro.c.topica.com/maadWviabj1F4ciD1pRb/ or see the "Observing
Meteors" booklet, free to all Section members by ordinary mail from our
Assistant Director Shelagh Godwin.


Scientists using the 'Swift' satellite say that they have found
new-born black holes, just seconds old, in a confused state of
existence. The holes are consuming material falling into them while
somehow propelling other material away at great speeds. The black
holes are born in explosions of massive stars: an initial blast
obliterates the star, yet the chaotic black-hole activity appears to
re-energize the explosion several times in just a few minutes. This
is a radically new view of star death, one that entails multiple
explosive outbursts, and not just a single one as had been thought.
The phenomenon has been seen in nearly half of the longer gamma-ray
bursts detected by Swift, which appear to be the most powerful
explosions known. They are forerunners of massive-star explosions
called hypernovae, which are bigger than supernovae. With Swift,
scientists are finally able to see gamma-ray bursts within minutes
after the trigger, instead of hours or days, and are privy to
new-born black-hole activity.

A particular example is a gamma-ray burst on 2005 May 2 in the
constellation Leo. The burst lasted 17 seconds; about 500 seconds
later, Swift detected a spike in X-ray light about 100 times brighter
than anything seen before. Swift has seen more than a dozen clear
cases of multiple explosions. Inevitably there are already several
theories to describe this newly discovered phenomenon, and most point
to the presence of a new-born black hole.


Astronomers have reported the discovery of the brightest cloud feature
ever observed on Uranus at near-infra-red wavelengths, in images
obtained with the 10-m Keck II telescope on August 14 and 15. On
Aug. 15 when it was near latitude 30 N and crossed the central
meridian, the feature was a complex of four parallel components
extending over 8 degrees of latitude and 13 degrees of longitude.

New Scientist

The performance of the James Webb Space Telescope, the future successor
to Hubble, should be reduced to cut cost overruns, say the astronomers
overseeing the telescope's development. The JWST, which is nominally
to be launched in 2011, will primarily study infra-red wavelengths, but
it has been designed to work at somewhat shorter wavelengths down to
0.6 microns. That falls into the range of visible light and overlaps
with the Hubble telescope, which is liable to fail as early as 2007
unless it receives new gyroscopes and batteries. But the JWST is
already $1 billion over its budget and scientists have recommended
reducing the shorter wavelengths that Webb can readily see. The
change would mean that the telescope would work only down to
wavelengths of about 1.5 microns, in the infra-red, but would not be
able to view the visible range down to 0.6 microns unless it were to
spend 50% longer on its observations. The limitation would result
from polishing the telescope's mirrors only once instead of twice,
saving $150 million and six months' labour. Some astronomers are far
from happy with that prospect and claim that the JWST had limited
optical performance anyway and to erode that further will really
jeopardise optical space astronomy in the next decade, leaving a gap.
Unlike Hubble, the JWST cannot be serviced in space, since it will
operate from a far more distant location, 1.5 million kilometres from

The Register

Observations of a mini-asteroid disintegrating as it entered the
Earth's atmosphere suggest that the resulting cloud is composed of
larger pieces of material than expected. The asteroid released as
much energy as a nuclear bomb on its way through the atmosphere,
according to the Australian Antarctic Division which studied the
progress of the thousand-ton shooting star in unprecedented detail,
using visible-light and infra-red equipment on orbiting satellites.
The team found fragments of the asteroid as large as 20 microns
across in the resulting dust cloud, big enough to have an impact
on the climate. Particles between 0.05 and one micron scatter light
and other radiation. The researchers say that, since the dust stays
in the atmosphere for weeks, sometimes months, meteors could play a
significant part in both ozone depletion and in altering the global
energy balance.


Evidence is mounting that the atmosphere of Enceladus, first detected
by the Cassini magnetometer instrument, is the result of venting from
ground fractures close to that moon's south pole. New findings from
the close fly-by of Enceladus by Cassini this past July add to the
emerging picture of a small icy body, unusual in its past and present
level of activity and very different from all other icy Saturnian
moons. Within a minute of closest approach to Enceladus on July 14,
two instruments on the spacecraft detected material coming from the
surface of the moon. The character of the detections was very similar
to that of the venting of vapour and small icy particles from the
surfaces of comets when they are warmed by sunlight as they near the
Sun. On Enceladus, however, it is believed that internal heat,
possibly from tidal forces, must be responsible for the activity.
Astronomers say that Enceladus is surprisingly warm, internally
fractured and active, but they do not claim to know why its south pole
is the warmest, most active place. The fact that Enceladus is so
alive whereas Mimas, the moon next to it and roughly the same size, is
so dead, is really demonstrating our ignorance of the internal
workings of planetary satellites. Cassini will encounter Enceladus
again at very close range in 2008.


A comprehensive survey has been made of more than 4,000 elliptical and
lenticular galaxies in 93 clusters of galaxies, including the largest
and richest ones, out to a distance of about a billion light-years.
Contrary to expectations, the largest, brightest galaxies in the
census consist almost exclusively of very old stars, with most of
their stellar populations having formed as much as 13 billion years
ago. There appears to have been very little recent star formation in
those galaxies, nor is there strong evidence for recent capture of
smaller, younger galaxies. By contrast, the smaller, fainter galaxies
are significantly younger -- their stars were formed as little as four
billion years ago. It seems, therefore, that when the Universe was
young, the star-formation activity occurred in large galaxies, but as
the Universe aged, the action stopped in the larger galaxies but
started or continued in smaller ones . Those results contrast sharply
with the conventional model, in which large elliptical galaxies formed
by swallowing smaller galaxies with young stars; that theory leads to
the expectation that, on average, the stars in the largest elliptical
galaxies should be no older than those in the smallest ones.

The evolutionary history of elliptical galaxies and lenticular
galaxies (which have a central bulge and a disc, but no spiral arms)
is not understood. Their colours are redder than those of typical
spiral galaxies. The largest ellipticals are the reddest of all, but
until now it had not been clear whether that resulted primarily from
greater age, as the survey found, or from having a higher proportion
of heavy chemical elements (higher metallicity content).


Astronomers using the VLBA radio telescope have discovered a neutron
star that is travelling so fast that it will pass out of our Milky Way
Galaxy into intergalactic space. Its discovery is puzzling
astronomers, who say it has the highest speed yet found in a neutron
star, more than 1000 km/s. It is the remnant of a massive star that
exploded in the constellation Cygnus about two and a half million
years ago. The object is known as B1508+55 and is about 8000 light-
years away.


Japan's Hayabusa spacecraft is scheduled to arrive at the main-belt
asteroid Itokawa in mid-September. Since its launch on 2003 May 9,
Hayabusa has been using an ion engine to propel itself steadily
towards the asteroid. If all goes according to plan, the spacecraft
will stay alongside Itokawa for about 5 months, mapping the surface
and making other observations. It should also become the first
spacecraft to collect samples from an asteroid's surface and to deploy
a tiny hopping robot, which can move around on the asteroid's
surface. After that, it will leave the asteroid and return to the
Earth in the summer of 2007, when a re-entry capsule containing the
minute samples will be released and parachuted to the ground. It is
hoped that samples from an asteroid would offer clues about the raw
materials that made up planets and asteroids in their formative years,
and about the state of the inside of the solar nebula around the time
of the birth of the planets.


£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

Bulletin compiled by Clive Down

(c) 2005 the Society for Popular Astronomy

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