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The SOCIETY for POPULAR ASTRONOMY
***********************************
====================================================
Electronic News Bulletin No. 173 2005 April 24
====================================================


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/maadrzOabglueciD1pRb/

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.


FIREBALL NEWS
By Alastair McBeath, SPA Meteor Section Director

Following the provisional report on the daylight fireball over the UK on the
morning of February 20 in ENB 170, a fresh report has arrived from Andy
Smith in Plymouth, who recorded a strong, single-meteor, radio signature
(see Andy's webpage at http://popastro.c.topica.com/maadrzOabglufciD1pRb/ for a
graph
of what he found) beginning at 09:55:20 +/- 10 secs UT. Although the
vagaries of the radio meteor detection method mean such strong radio
signatures do not always equate with fireball-class meteors, the chance of
such an event being detected at effectively the same time as visual observers
reported seeing a brilliant meteor is small enough to be discounted in this
case, thus refining the time for the fireball much more closely than the
original 09:54 +/- 1 min UT.

More recently, a single witness in Lincolnshire spotted a very bright fireball
from indoors around 01:30 UT on April 4-5. This came at the end of a
busy few days for European bright fireball observations, as an event over
southern Sweden, which was widely-seen from Denmark, occurred at
20:05 UT on April 2-3, followed by another fireball caught on video by the
Polish fireball network overnight on April 3-4. Early April at least thus
seems to have lived up to the month's reputation as a sometimes good
fireball-producing one!

Fireball sightings from the UK and nearby areas are always welcomed by
the SPA Meteor Section. Details on what to report and where to can be
found on the "Fireball Observing" page, off the Section's homepage at:
http://popastro.c.topica.com/maadrzOabglugciD1pRb/


EUROPEAN MARS LANDER PLANS
BBC Online

Europe has confirmed its intention to try again to land on Mars, to
search for evidence of past or present life. The European Space
Agency mission, which would include a roving robot, would leave Earth
in 2011 June and arrive two years later. The 500-million-euro mobile
laboratory would sniff the air for signs of biology and listen to the
ground for evidence of Marsquakes. ESA's last landing attempt, Beagle
2, went missing without a trace in 2003. The exact nature of the
mission will not be decided for several months, but the spacecraft is
likely to include a drill or 'mole' that could help investigate the
sub-surface chemistry, and experiments that would analyse the soil,
rocks and atmospheric gases for signs of biological activity.
Sample return is ruled out as being too expensive.


EXTRASOLAR PLANET OR BROWN DWARF?
Science News

Last year it was claimed that a tiny dot of light recorded next to the
young, sunlike star GQ Lupi represented the first direct sighting of
an extra-solar planet. It now seems more likely to most astronomers
working in the subject to be a brown dwarf star and not a planet at all.


ENORMOUS TELESCOPES PLANNED
BBC Online

A new generation of ground-based telescopes could be up to 10 times
the size of existing instruments and provide resolution 40 times
better than the Hubble space telescope. Extremely large telescopes
are vital if the pace of astronomical breakthroughs is to continue,
say experts. Concepts include the Thirty-Metre Telescope (TMT) being
considered by the US and Canada; and the Euro50 and Overwhelmingly
Large Telescope (OWL) proposals put forward by Europe. The size of
any European telescope has not yet been agreed, but the European
Southern Observatory's OWL concept would be by far the largest
telescope ever built, with a spherical primary mirror up to 100m
across.

Building such gargantuan observatories poses substantial technical
challenges, as it is not practicable to make a mirror bigger than
about 8m across in one piece. Some designs for very large telescopes
involve combining several circular 8-m mirrors, but others, including
the OWL, would have mirrors constructed from many small hexagonal
segments. The OWL design uses a spherical, rather than the usual
paraboloidal, mirror shape to cut down on cost. That means that its
segments can all be the same shape and size and can be mass-produced,
but it also necessitates several corrective mirrors. The OWL concept
works for a telescope of around 100m, but below the 60-m mark the
Euro-50 design, which has a paraboloidal mirror, may strike a better
deal between cost and performance.


SIGNATURES OF THE FIRST STARS
Subaru Observatory of Japan

An international team of astronomers reports the discovery of a star,
HE1327-2326, which has a greater deficiency of heavy elements in its
atmosphere than any star previously analysed. Its chemical
composition, as measured with the Subaru Telescope, provides evidence
of nucleosynthesis by the first generations of stars in the Universe,
and places new constraints on their masses and on the metal-enrichment
history in the very early Universe.

The first generation of stars is believed to have formed several
hundred million years after the Big Bang, which occurred about 14
billion years ago. Those stars were part of the transition from a
Universe that consisted only of hydrogen and helium to one that
contains a variety of elements and objects including stars and
galaxies. Recent theoretical studies of the first stars to form in
the Universe suggest the formation of super-massive stars (several
hundred times the mass of the Sun and not seen in the present-day
Milky Way galaxy). In addition, the theories do not predict the
formation of low-mass stars like the Sun in the early Universe. There
is, however, no clear observational evidence for those predictions to
date. One possible source of evidence is very old stars in our
galaxy. They contain only small amounts of heavy elements, in
particular iron. Their abundance patterns constrain the
nucleosynthesis models of first-generation stars and their mass
distribution. First-generation low-mass stars, which contain almost
no heavy elements, might also be found among iron-deficient stellar
populations.

The Subaru observation revealed that the star's iron abundance is only
1/250,000 that of the Sun, but the carbon and nitrogen abundance
ratios relative to iron are remarkably high. There is a close analogy
with another iron-deficient star, HE0107-5240, which was found in
2001. The metal-enrichment histories of those two stars seem to be
quite different from those of other metal-deficient stars. The
elemental abundance patterns of HE1327-2326 and HE0107-5240
provide clues to the nucleosynthesis of first-generation stars and their
formation processes. A possible explanation of the chemical abundance
patterns of the two stars involves the postulation of 'peculiar'
supernovae that provided only small amounts of heavy elements like
iron. In that case, then, the star we are currently observing should
be a second-generation star that was seeded with heavy elements by a
first-generation supernova.


NEW IDEAS ABOUT SEDNA
New Scientist

A new study suggests that the distant planetoid Sedna is covered in a
tar-like hydrocarbon sludge that gives it a distinctly reddish hue.
Sedna was discovered in 2003 November and appears to be nearly as big
as Pluto. It is the most distant object known in the Solar System and
travels on an elongated path that stretches from 74 to 900 times the
distance between the Sun and the Earth. Astronomers have struggled to
explain such an extreme orbit, but there has been some speculation
that it arose from the effect of a star passing nearby early in
Solar-System history. Now, new observations by the team that
discovered Sedna suggest that the object has since led an uneventful
existence. Infrared spectra taken at the Gemini telescope in Hawaii
show that the surface of the planetoid contains little methane ice,
found in significant amounts on Pluto, and little water ice, seen on
Pluto's moon, Charon. Collisions with other objects may have helped
expose the icy interiors of Pluto and Charon and a lack of collisions
might explain Sedna's ice-free surface. Sedna, which is probably made
up of a mixture of ices and rock, may be covered with a metre or so of
hydrocarbon sludge, produced by the Sun's ultraviolet radiation and
charged particles altering the chemical bonds between atoms in the
ices.


SPECULATION ABOUT MINI BLACK HOLES IN EARLY UNIVERSE
Institute of Physics

A research group at Cambridge thinks that the Universe might once have
been full of tiny black holes. Fashionable cosmologists believe that
supermassive black holes grew up in big galaxies, accumulating mass as
time went on. But the dissident group claims that there is increasing
evidence for a different view -- that small black holes grew
independently and merged to produce the giants which are thought to
exist today. They point to evidence from recent studies of the cosmic
microwave background (CMB) which has been travelling unaltered through
space since the Universe was just 400,000 years old. At that moment
the Universe cooled through a critical point, letting CMB radiation
travel freely for the first time -- as though a cosmic fog had lifted.
But new evidence suggests that 10 to 15 per cent of the radiation has
been scattered since then. That is being held to indicate a
re-warming, which nobody had expected, of the Universe, and which
might be attributable to the heating caused by accretion of matter
onto a lot of small black holes.




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To order, simply call the publisher's warehouse on 01903 828503 and
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OFFER ENDS 2005 MAY 21.

Bulletin compiled by Clive Down

(c) 2005 the Society for Popular Astronomy


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