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The SOCIETY for POPULAR ASTRONOMY
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Electronic News Bulletin No. 187 2005 December 20
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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/maaejNgabmTBdcixLLVb/

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


IoA DEVELOPS LUCKY IMAGING
BBC News

Astronomers at the Institute of Astronomy, Cambridge, have developed a
low-cost camera technique that they call `lucky imaging' which helps
to sidestep the problem of atmospheric turbulence. The group's camera
takes lots of images very quickly in the hope that just a few are not
blurred, and it is claimed that the clearest pictures are as sharp as
those captured by the Hubble Space Telescope. Lucky imaging is an
approach previously used only by amateurs, who cannot afford the
imaging methods now used on the most sophisticated telescopes.
A great deal of money has been spent elsewhere on `active' and
`adaptive' optics, which use complicated systems of mirrors and
computers to get detailed pictures, but the Institute of Astronomy
project has so far cost just £20,000. Scientists fitted a new camera
to the 2.56-m Nordic Optical Telescope in the Canary Islands. They
observed 48 stars, and by choosing only the clearest images they
discovered that 10 of them were actually low-mass binary stars.


SECOND SATELLITE FOR 2003 EL61
IAU

Astronomers using the Keck II telescope report the discovery of a
second satellite of the transneptunian object 2003 EL61. The
satellite is more than four magnitudes fainter than the primary and
appears to have a circular orbit with a 34.1-day period. 2003 EL61 is
the third-brightest Kuiper-belt object, after Pluto and 2005 FY9.
About 10% of Kuiper-belt objects have satellites, but until recently
no other object in the Kuiper belt was known to have more than one.
Recently, however, two additional small satellites were discovered
around Pluto.


BLACK-HOLE PLUMES
Space.com

Observations by the Chandra X-ray observatory have revealed energetic
plumes of particles associated with the massive Perseus cluster of
galaxies. The results provide evidence that a black hole can
influence the space around it to intergalactic distances, researchers
said. The Perseus cluster contains thousands of galaxies, all
embedded in a cloud of superheated gas. The gas alone has the mass of
millions of millions of Suns. The plumes, seen clearly in enhanced
images from X-ray data, are low-pressure regions in the hot gas
extending outward from the central galaxy, NGC 1275, which is one of
the largest galaxies known. The low pressure may be the result of the
displacement of the gas by unseen high-energy particles shot out from
the supermassive black hole thought to lie in NGC 1275. The plumes
indicate that the black hole has been venting for at least 100 million
years, and probably much longer. The venting produces waves that heat
the gas throughout the inner regions of the cluster and prevent it
from cooling and making stars at a significant rate. The process may
have slowed the growth of NGC 1275.


UK SIGNS UP TO MARS MISSION
BBC News

European Space Agency member states have approved funding for the
ExoMars mission -- a key milestone in the Aurora programme, ESA's
vision to send spacecraft and eventually astronauts to the Moon and
Mars. In the near term, it focuses on robotic missions -- ExoMars in
2011, followed by an international Mars sample-return mission.
Science minister Lord Sainsbury said that, as a major contributor, the
UK will have a leading role in the programme, which should improve our
understanding of Mars and the Solar System. The bulk of the money
will be used to develop ExoMars, with the rest being used for basic
research into future missions to the Moon and Mars. The UK is
contributing £73m out of a total subscription of around £508m. That
should give British industry a considerable share of the work, perhaps
allowing it to regain confidence lost as a result of the ill-fated
Beagle 2 mission.


GALAXY COLLISIONS DOMINATE LOCAL UNIVERSE
Yale University

About half of the largest galaxies in the `nearby' part of the
Universe have collided and merged with other galaxies in the past two
billion years, according to a study based on deep sky surveys made
with the 4-m telescopes at Kitt Peak and CTIO. The idea of large
galaxies being assembled primarily by mergers rather than evolving by
themselves in isolation has grown to dominate cosmological thinking.
Astronomers hoping to substantiate that idea looked for telltale tidal
features around 126 nearby red galaxies, a colour selection biased to
select the most massive ones. Faint tidal features turned out to be
quite common, with 53% of the galaxies showing tails, broad fans of
stars trailing behind them or other obvious asymmetries. The
collisions that precede the mergers are ongoing in many cases,
allowing the astronomers to study galaxies before, during, and after
collisions. Though there are not many direct, star-to-star encounters
in the merger process, galaxy collisions can have profound effects on
star-formation rates and the shapes of the resulting galaxies.


MARS ROVERS CONTINUE TO EXPLORE
NASA

The twin Mars rovers have successfully explored the surface of the
planet for a full Martian year (687 Earth days). The rovers' original
mission was scheduled for only three months. Both rovers keep finding
new variations of bedrock in the areas that they are exploring on
opposite sides of Mars. The `geo'logical information that they have
collected suggests that ancient Martian environments included periods
of wet conditions. Aided by a power supply from batteries charged by
Spirit's solar cells, researchers have been using one of the rovers at
night for astronomical observations. One experiment watched the sky
during a meteor shower as Mars passed through the debris trail left by
a passage of Halley's comet.


SPIRAL ARM IS CLOSER THAN SUPPOSED
New Scientist

One of the Milky Way's star-studded spiral arms lies only half as far
from Earth as some estimates had suggested. Certain astronomers had
estimated the distance to Perseus, the arm immediately beyond the Sun,
at more than 13,000 light years, by modelling the observed motions of
some of its stars on the assumption that they revolve around the
centre of our galaxy in circular orbits. Other researchers arrived
at half that distance by comparing the apparent brightnesses of
massive young stars with estimates of their intrinsic brightnesses.
Now astronomers have used a third and much more accurate technique:
using the Very-Long-Baseline Array of radio telescopes, they managed
to measure the parallaxes of a number of methanol masers in a
star-forming region called W3OH in the Perseus arm. They concluded
that the arm is indeed relatively close, at 6400 light-years from
Earth. They also found that W3OH is not moving in a perfectly
circular galactic orbit but instead follows an elliptical path, as if
drawn along the Perseus spiral arm.


MOVEMENT OF THE EARTH'S MAGNETIC POLES
AP

The Earth's north magnetic pole is drifting away from North America
and toward Siberia at such a speed that Alaska might lose its
spectacular Northern Lights in the foreseeable future. In spite of
accelerated movement over the past century, the possibility that
Earth's modestly fading magnetic field will collapse is remote, but
the shift could mean that aurorae might become more visible in more
southerly areas of Siberia and Europe. The magnetic poles mark the
axis of the magnetic field generated by liquid iron in the Earth's
core and are far from coinciding with the geographical poles.
Scientists have long known that the magnetic poles migrate, and that
at long intervals they exchange places, although why they do so is
unknown. Previous studies have shown that the strength of the field
has decreased by 10% over the past 150 years; during the same period,
the north magnetic pole has wandered about 685 miles out into the
Arctic. The rate of movement has increased in the last century in
comparison with the fairly steady movement of the previous four
centuries.


HIGHLY INCLINED ORBIT IN THE KUIPER BELT
New Scientist

Canadian astronomers using the Canada-France-Hawaii Telescope have
found a large object in the Kuiper Belt beyond Pluto, travelling in
an orbit tilted by 47 degrees to the plane of most other orbits in
the Solar System. Tentatively named 2004 XR190, the object appears
to have a diameter of between 500 and 1000 kilometres, making it
somewhere between a fifth and two-fifths the size of Pluto. Neptune
has been blamed for scattering many other Kuiper-Belt objects into
tilted paths, but they tend to show other signs of a past interaction
with Neptune, such as moving in elliptical paths and having their
perihelia near Neptune's orbit at 30 AU from the Sun. 2004 XR190,
however, follows a nearly circular path between 52 and 62 AU from the
Sun, so it is never anywhere near Neptune.


MASS OF SIRIUS B DETERMINED
STScI

An international team of astronomers has used the Hubble Space
Telescope to observe the spectrum of the white dwarf Sirius B. The
new results allow the white dwarf's mass to be determined from the red
shift caused in the spectrum by its intense gravitational field.
Scattered light from the very bright Sirius A, only a few seconds of
arc away, has presented great difficulties for Earth-based observers.
Sirius B has a diameter of 7,500 miles, less than the size of the
Earth, but it is enormously dense. Its gravitational field is 350,000
times greater than ours. The new measurements show that Sirius B has
a mass that is 98% of that the Sun; Sirius itself has a mass twice
that of the Sun and a diameter of 1.5 million miles.


PHILIP'S NEW TITLES:

Philip's The Sky at Night Volume 2 is the latest volume in Sir Patrick
Moore's series of essays written to accompany the BBC television
series of the same name. It tracks the most important developments in
astronomy, astrophysics and space exploration in the period from 2001
November to 2005 March -- £9.99
Philip's Stargazing 2006 by Heather Couper and Nigel Henbest.
Stargazing 2005 was a popular addition to Philip's astronomy list last
year, and the 2006 edition of this month-by-month practical guide to
the changing night sky is expected to be equally well received. - £6.99
Published this month:
Philip's Solar System Guide by Peter Grego contains an abundance of
information and images, and is a practical and colourful introduction to
our corner of the Universe. It describes how to observe not only the
planets but also the Moon, Sun, comets, meteors, asteroids and other
objects found within our Solar System -- £9.99
Philip's Solar System Observer -- a brand-new pack for the amateur
Solar-System observer. It contains three essential items for exploring
and enjoying our corner of the Universe: Philip's Solar Observer's
Guide, Philip's Map of the Solar System and Philip's Solar System
Phenomena poster -- £12.99
For more information on those and other Philip's titles please visit
www.philips-maps.co.uk or call 020 7644 6935 for a catalogue.


Bulletin compiled by Clive Down

(c) 2005 the Society for Popular Astronomy


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