ENB No. 196 May 14 2006

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ENB No. 196 May 14 2006

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Electronic News Bulletin No. 196 2006 May 14

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/maaeNGnabqyY8cixLLVb/

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.


Saturn's moon Titan has regions covered with dunes, made of
unidentified granular material. Images transmitted from Cassini look
very much like terrestrial sand dunes. The radar images show the
dunes to be up to 500 feet high and hundreds of miles long. Dark
patches were at first thought to be seas, but now they appear to be
largely dunes. The existence of dunes, piled over other topographical
features, suggests that there must be winds, that recently blew fine
grains of some material around.

New Scientist

A recent addition to the list of 'potentially hazardous' asteroids
is one called 2006 HZ51, discovered on April 27. It has an
estimated diameter of about half a mile and is one of the largest
objects to make the list. It will make a close approach quite soon,
on 2008 June 21. An object of its size would cause widespread
devastation if it actually struck the Earth, and the discovery of such
an object that will make a close pass at such short notice brings to
attention the fact that little could be done to mitigate an impending
impact that was recognized with only such a short lead time.

BBC News

A Ministry of Defence report, recently made public, on unidentified
flying objects has concluded that there is no proof of alien life
forms. The 400-page report sums it up like this: "No evidence exists
to suggest that the phenomena seen are hostile or under any type of
control, other than that of natural physical forces. There is no
evidence that 'solid' objects exist which could cause a collision
hazard. Evidence suggests that meteors and their well-known effects,
and possibly some other less-known effects, are responsible for some
unidentified aerial phenomena. Considerable evidence exists to
support the thesis that the events are almost certainly attributable
to physical, electrical and magnetic phenomena in the atmosphere,
mesosphere and ionosphere. They appear to originate from more than
one set of weather and electrically-charged conditions and are
observed so infrequently as to make them unique to the majority of

People who claim to have had a 'close encounter' are often difficult
to persuade that they did not really see what they thought they
saw. The report offers a possible medical explanation, related to
plasma fields affecting the brain. There are, of course, other and
more mundane causes of UFOs -- aeroplanes with particularly bright
lights, stray balloons and flocks of birds, to name but a few.


Indications have been found in recent years that galaxies cluster
in filaments and sheets surrounding vast voids in space. Now,
astrophysicists at the University of Nottingham have performed a
statistical study of the orientations of galaxies surrounding the
voids. They studied 470 of the largest voids -- galaxy-studded shells
hundreds of millions of light-years across. They found the voids by
sifting through two large-scale studies of galactic redshifts. They
concluded that significantly more spiral galaxies spin with their axes
aligned with the filaments in which they are embedded than would be
expected by chance.


While observing the extremely distant quasar PSS J 1443+2724,
astronomers detected several features belonging to an unseen
intervening galaxy having a redshift of 4.22 in the same line of
sight. In particular, many spectral lines from molecular hydrogen
were found, breaking the distance record for such a detection. The
existence of molecular hydrogen implies that the gas in the galaxy
must be rather cold, about -90 to -180 degrees Celsius. Several lines
from heavier elements were also seen, allowing estimates to be made of
elemental abundances. The astronomers claim that the nitrogen
abundance could only have arisen in late evolutionary stages of
stars of 4 to 8 solar masses. That would imply that star-formation
activity must have operated at least 200 to 500 million years before
the galaxy reached the age at which we see it now, that is, when the
Universe was about one billion years old, but the galaxy does not
appear very active in our present view.


A new map of stars in the Milky Way Galaxy, constructed with data from
the Sloan Digital Sky Survey, reveals the sky to be criss-crossed with
streams of stars left behind by satellite galaxies and star clusters
disrupted by the tidal forces of the Milky Way. As the satellites
are disrupted, stars that are torn from them are left in streams that
trace their orbital paths, rather as meteor streams lie along the
paths of comets in the Solar System. The most conspicuous stream,
already known before the recent mapping, is that of the Sagittarius
dwarf galaxy. The stream appears forked, and different wraps are
superimposed on the sky, as the stream goes round the Galaxy two or
three times. In addition to the Sagittarius stream, there are faint
trails of stars torn from globular clusters, and other rings, trails,
and lumps that appear to be the remains of disrupted dwarf galaxies.
Crossing the new map is a stream of stars, extending over 70 degrees
on the sky, whose original source remains unknown. The new
discoveries add weight to a picture in which galaxies like the Milky
Way are built up from the accretion and merging of smaller galaxies.


The map mentioned in the previous item shows two new, very faint
dwarf companion galaxies to the Milky Way, in the directions of the
constellation Canes Venatici and Bootes. The one in Canes Venatici is
about 640,000 light-years from the Sun, making it one of the most
remote of the Milky Way's companion galaxies. The even fainter dwarf
galaxy found in Bootes shows a distorted structure that suggests that
it is currently being disrupted by the Milky Way's gravitational tides.

BBC News

A US study has found that certain meteorites contain simple carbon
compounds. It was previously thought that the only way to investigate
early molecules was to collect interstellar dust -- the idea behind
space missions such as Stardust. Carnegie scientists analysed six
carbonaceous chondrite meteorites. They looked at the relative
proportions of different isotopes among the nitrogen and hydrogen
atoms involved in the carbon compounds. Their analysis found an
excess of heavier isotopes -- something also found in interstellar
dust grains. They concluded that the meteorites contained material
that had been largely unaltered since the time when the Solar System
was formed from the collapse of a cloud of gas and dust.

BBC News

A half-metre fragment has been retrieved of the asteroid whose
impact, 145 million years ago, created the 100-mile Morokweng crater
in South Africa. The crater is one of the largest on Earth, and was
formed at the boundary of the Jurassic and Cretaceous periods.
Created by an asteroid that must have measured 5 to 10 km across,
the impact bowl lies hidden beneath the sands of the Kalahari Desert.
Scientists found the fragment by drilling boreholes into the impact
melt -- the area where the asteroid fused with the Earth -- in the
centre of the crater.


There has been a suggestion that sunspot activity is related to the
speed of movement of a belt, or circulating current of hot plasma,
beneath the visible surface of the Sun. Its speed has been estimated
from historical sunspot records as far back as 1890, and appears to be
correlated with the intensity of sunspot activity about 20 years
later. On that basis the solar cycle that is now starting and is due
to peak in 2011 or 2012 will be intense, but a recent slowdown in the
belt would be interpreted as forecasting that the following one,
peaking in about 2022, should be a particularly weak one. That could
be seen as good news for astronauts, who according to present plans
should then have returned to the Moon and be preparing to go to Mars
and should be at less risk from solar flares and radiation storms.


Philip's The Sky at Night Volume 2 is the latest volume in Sir
Patrick Moore's series of essays written to accompany the television
series of the same name. It tracks 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.
A month-by-month guide, now partly otiose - £6.99
Published last year:
Philip's Solar System Guide by Peter Grego describes how to observe
not only the planets but also the Moon, Sun, comets, meteors,
asteroids and other objects in our Solar System -- £9.99
Philip's Solar System Observer -- a pack for the amateur Solar-System
observer. It contains three items: 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) 2006 the Society for Popular Astronomy
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