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The SOCIETY for POPULAR ASTRONOMY
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Electronic News Bulletin No. 190 2006 February 5
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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/maaesNSabn4nocixLLVb/

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.


SPA COMET NEWS January 2006
By Jonathan Shanklin

Comet news has been rather thin over the last six months, and there is
little new to report now. SOHO duly passed its 1000th comet in August
and is still going strong. Several more of the non-Kreutz comets
found by SOHO have been shown to be returning fragments of what Zdenek
Sekanina describes as the Sunskirting complex, including two of my own
discoveries. These comets only get to around 0.06 AU from the Sun, so
are not Sungrazers like the great comets of the Kreutz group.
Stardust has returned after its encounter with comet 81P/Wild and
scientists are now feverishly working on the precious comet dust
trapped by the aerogel.

The IAU has agreed the naming scheme for comets (which I've been using
for several years), so names like Comet Tempel 1 should no longer be
used in any publications. The old scheme was very confusing at times,
and as you will see in an upcoming opinion is Astronomy Now, I'm
offering a small prize for the first correct identification of a
specific comet LINEAR. To keep things fair I'm not telling you which
one -- you'll have to buy the magazine. I'll run a separate
competition for SPA members to identify comet NEAT 18 and give me
reasons for your suggestions. I'm convinced by the arguments that
Pluto is not a planet. At the moment Pluto is just creeping into the
morning sky and it is a demanding challenge at the best of times, but
just about achievable visually with a 20-cm telescope from a dark site.

Prospects for comet 2005 E2 (McNaught) are not as good as I expected
in the last newsletter, and the comet is a difficult object of around
10th magnitude. A new comet has been discovered, but it is currently
in the far southern sky. It will come into view for UK observers in
early March, but is then visible only in the early-morning sky, and
will quickly fade from 8th magnitude. A more interesting prospect is
the return of comet 73P/Schwassmann-Wachmann. It split into several
fragments at its return in 1995, when it underwent a spectacular
outburst. Its activity has declined a bit, however it makes a very
close pass to the Earth and could become a naked-eye object in May.
So far the main body and a fragment have been recovered and it looks
as if the comet may reach binocular brightness by the end of March.
I'll give more details in the next newsletter, by which time we should
be more certain on how bright it will be, and we will let you know
exactly where to look for the fragments.

I'm paying another visit to the Antarctic and will be away from the
end of January until late March. I'm spending most of the visit at
stations on South Georgia, which is roughly as far south as Manchester
is north. I hope Mancunians will forgive me for saying that I'm not
expecting much from the weather! You should be able to contact me via
email, but answers to letters will have to wait until my return,
though you could try writing to me c/o British Antarctic Survey,
Stanley, Falkland Islands.


SMALL EXOPLANET DISCOVERED
ESO

Using a network of telescopes scattered across the globe, astronomers
have discovered a new extrasolar planet significantly more Earth-like
than any found so far. The planet, which is only about 5 times as
massive as the Earth, circles its parent star in about 10 years. It
is the least massive exoplanet detected around an ordinary star so far
and also the coolest. It almost certainly has a rocky/icy surface.
Designated by the unglamorous identifier of OGLE-2005-BLG-390Lb, it
orbits a red-dwarf star one-fifth as massive than the Sun and located
at a distance of about 20,000 light-years, not far from the centre of
our Milky Way galaxy. Its relatively cool parent star and large orbit
imply that the surface temperature must be about 220 degrees
Centigrade below zero. It is likely to have a thin atmosphere, like
the Earth, but its rocky surface is probably deeply buried beneath
frozen oceans. It may therefore more closely resemble a more massive
version of Pluto, rather than the rocky inner planets like Earth and
Venus. The planet is actually the only one that has been discovered
so far that is at all in agreement with the theory for how our Solar
System formed. That proposes that solid 'planetesimals' accumulate to
build up planetary cores, which then accrete nebular gas -- to form
giant planets -- if they are sufficiently massive. Around red dwarfs,
the most common stars of our Galaxy, the model favours the formation
of Earth- to Neptune-mass planets being between 1 and 10 times the
Earth-Sun distance away from their host.

Contrary to most exoplanets discovered, OGLE-2005-BLG-390Lb was
found by the 'microlensing' technique, based on an effect noted by
Albert Einstein in 1912. With that method, the gravity of a dim,
intervening star acts as a natural telescope, magnifying a more
distant star, which then temporarily looks brighter. A small 'defect'
in the brightening reveals the existence of a planet around the lens
star. Astronomers don't see the planet, or even the star that it's
orbiting, but just the effect of their gravity. Such an intervening
star causes a characteristic brightening that lasts about a month. Any
planets orbiting the star can produce an additional signal, lasting
days for giant planets down to hours for Earth-mass planets.
OGLE-2005-BLG-390Lb is only the third extra-solar planet discovered so
far through microlensing searches. While the other two microlensing
planets have masses of a few times that of Jupiter, the discovery of a
5-Earth-mass planet -- though much harder to detect than more massive
ones -- may be a hint that such lower-mass objects are common.


RUSSIA TO OPEN MOONBASE MINE
Agence France-Presse

The Energia space corporation claims that Russia is planning to mine
the Moon for the rare isotope Helium-3. It plans to build a permanent
base on the Moon by 2015 and by 2020 to begin industrial-scale
delivery. The International Space Station (ISS) would play a key role
in the project and a regular transport relay to the Moon would be
established with the help of the planned Clipper spaceship and the
Parom, a space capsule intended to tug heavy cargo containers around
space. Helium-3 is a non-radioactive isotope of helium that can be
used in nuclear fusion. Rare on Earth but plentiful on the Moon, it
is seen by some experts as an ideal fuel because it is powerful,
non-polluting and generates almost no radioactive by-product.


MILKY WAY BRIMS WITH SINGLE STARS
New Scientist

A new analysis suggests that most of the stars in the Milky Way are
born alone and live out their lives without partners. If so, the work
overturns standard theories that stars are born in broods and also
suggests that planets may be more common in the galaxy than thought.
Observations show that stars are born in nurseries of gas and dust
that typically contain several hundred stars in a region 3 light-years
across. According to most models, they are born there in clutches,
with several stars condensing from each of many large, dense clouds of
matter.

Now, an astronomer at the Harvard-Smithsonian Center for Astrophysics
is challenging that notion and says stars are born alone in the
nurseries. He says that the models are based on early stellar surveys
that focussed on bright, relatively massive stars like the Sun. The
surveys found that about 60% of those bright stars are found in pairs.
But in the last 15 years or so, astronomers have used more sensitive
telescopes to survey smaller, dimmer red dwarfs, which are between 10%
and 50% the mass of the Sun. The faint stars are harder to see, but
they make up 85% of all stars in the galaxy, and three-quarters of
them are single. The result strongly favours the idea that most stars
form initially as single objects, not in multiple systems. That goes
against current models, which explain the existence of single stars by
arguing that they are born with siblings and are then separated after
gravitational interactions with other stars.


TWO STARS LEAVING MILKY WAY
Harvard-Smithsonian Center for Astrophysics

Astronomers using the MMT Observatory in Arizona have discovered two
stars racing outwards from the Galaxy at speeds of more than 1 million
miles per hour -- so fast that they will never return. The latest
discovery brings the total number of known exiles to five.
Astronomers suspect that about 1,000 exile stars exist within the
Galaxy. By comparison, the Milky Way contains about 100 billion
stars, making the search for exiles much more difficult than finding
the proverbial needle in a haystack. It is suggested that the exiled
stars were thrown from the Galactic Centre millions of years ago.
Each star once was part of a binary star system. When a binary passes
too close to the black hole at the Galaxy's centre, the intense
gravity can disrupt the binary, capturing one star while flinging the
other outward at tremendous speed (hence their technical designation
of hypervelocity stars). The two recently discovered exiles are both
short-lived stars about four times as massive as the Sun. Many
similar stars exist near the Galactic Centre. Moreover, detailed
studies of the Milky Way's centre have found stars orbiting the black
hole on very elongated, elliptical orbits -- the sort of orbits that
would be expected for former companions of hypervelocity stars.


KUIPER BELT OBJECT LARGER THAN PLUTO
BBC News

An icy, rocky planet found last year to be orbiting the Sun in the
distant reaches of the Solar System really is bigger than Pluto,
scientists say. New observations of the object, which goes by the
designation 2003 UB313, show it to have a diameter of some 3,000 km --
about 700 km more than Pluto. The measurement was undertaken by a
German team using a Spanish telescope. Like Pluto, 2003 UB313 orbits
beyond Neptune in a region known as the Kuiper Belt. The figure of
3,000 km could be in error by up to 10%, but in any case it still
represents the largest object found in the Solar System since Neptune
in 1846. Astronomers have nicknamed the object Xena.


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 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 last year:
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 pack for the amateur Solar-System
observer. It contains three 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) 2006 the Society for Popular Astronomy


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