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The SOCIETY for POPULAR ASTRONOMY
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Electronic News Bulletin No. 189 2006 January 22
====================================================


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/maaep28abnI6kcixLLVb/

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


PRELIMINARY 2006 QUADRANTID PEAK NEWS
By Alastair McBeath, SPA Meteor Section Director

Parts of Scotland and northern England were the places to be on January
3-4 in Britain, near the expected Quadrantid maximum (due at around
18:30 UT that night), from results in so far. Most of the British Isles,
like
much of Europe, lay under a heavy swathe of clouds, fog and rain,
apparently. Some early comments from the UK can be found on the
"Quadrantids 2006" topic on the SPA's Observing Forum, at:
http://popastro.c.topica.com/maaep28abnI6lcixLLVb/ .

Mike Dale in Edinburgh and the Director have provided the most detailed
reports directly so far, along with the Forum comments, and notes from
SPA Aurora Director Ian Brantingham on the Moray Firth, plus Section
correspondent and American Meteor Society activist Bob Lunsford in
California, USA. Zenithal Hourly Rates (ZHRs) from Britain look to have
been in the 50s by midnight UT, declining through the 40s to 30s as the
night progressed. A couple of casual early evening reports indicated
that a
few, often long-pathed, Quadrantids had been spotted from the UK
around 17:00-20:30 UT, while the radiant was at its lowest for the day
from here, which might imply the maximum kept to its expected time.
However, other observers reported no Quadrantids from a similar
interval,
so this is not yet certain.

The preliminary International Meteor Organization report, issued on the
IMO-News e-mailing list on January 8 (see
http://popastro.c.topica.com/maaep28abnI6mcixLLVb/ was
also beset by too few observations over the critical times, but
suggested
ZHRs reached their best around 23:00-00:00 UT on January 3-4, at a
lower level than expected (about 85 +/- 17). The lack of results much
before 19:00 UT, and the small number of datasets even for this possible
"peak" interval, mean this is far from conclusive. The initial SPA
results
did not suggest ZHRs this high near midnight UT certainly, so more data
are needed urgently to try to refine these findings.

Consequently, all further observations from early January would be
gratefully received. Advice on what to report and where to can be found
via the SPA meteor homepage at:
http://popastro.c.topica.com/maaep28abnI6ncixLLVb/ .


RECENT FIREBALLS
By Alastair McBeath, SPA Meteor Section Director

A small "clump" of fireball sightings came in to the Section from late
December and early January, including the following: December 25-26,
~02:25-02:30 UT (Bristol); December 28-29 at 17:50 +/- 2 mins
(Glean Spean, Highland) and ~19:15-19:30 UT (Lincolnshire); and
January 1-2, 00:39 UT (two sightings, Arran and Glasgow). These do
not include the few definite Quadrantid bright to fireball-class meteors
(a
fireball is a meteor that reaches at least magnitude -3) on January 3-4,
incidentally.

Then a spectacular magnitude ~-13 event came down at 22:41 +/- 10
mins UT on January 11-12, probably over central, or central-southern,
England. Seven sightings have been received now, scattered across
England from near Blackpool on the Lancashire coast, south to Luton and
Buckinghamshire, via the West Midlands. More observations with full
positional details would be welcome, to try to pin down the object's
atmospheric trajectory. Information on what to report and where to can
be found on the SPA's "Fireball Observing" page, off the meteor
homepage. Another very bright fireball happened on January 14-15 at
about 20:29 UT.


LATEST SECTION PUBLICATION
By Alastair McBeath, SPA Meteor Section Director

The Meteor Section's 2004 "Annual Review" was published on 2006
January 17, with a round-up of the main meteoric (and some not-so-
meteoric, but significant) events during the year, plus all the usual
features.
Printed copies only are available, from Assistant Director Shelagh
Godwin. Please send her an A5 SAE with your request, to her postal
address from the recent SPA News Circular. Shelagh also has back
issues of our previous recent "Annual Reviews", as well as our Special
Report "The Leonids 1998-2002 - A Retrospective", issued as part of
the Section's contribution to the inaugural SPA Convention in Cambridge,
last October. If you'd like any of these, send Shelagh a separate A5 SAE
for each item requested.


AMATEURS ENCOURAGED TO HUNT SUPERNOVAE
Ohio State University

Astronomers searching for elusive neutrinos are asking amateurs to
hunt for supernovae in nearby galaxies. Neutrinos should be
everywhere, but they are very hard to detect -- so hard to detect, in
fact, that even though countless neutrinos burrow through our planet
every second, scientists capture only a few of them each day.
Scientists know that most of the neutrinos that they do detect
probably come from our own Sun, from nuclear reactors in terrestrial
power plants, or from cosmic radiation interacting with our
atmosphere. There has been no way to distinguish whether a particular
neutrino came from elsewhere, until now. That's why a discovery --
that each year, one or two of the neutrinos detected on Earth can
probably be matched to the exploding star that made them -- represents
a major step forward for supernova astrophysics. The method will
fully exploit the capabilities of the next generation of neutrino
detectors, which are now being planned, and take advantage of the
growing number of amateur astronomers who are capable of discovering
supernovae.

Researchers claim that if a detector on Earth registers two of the
particles within ten seconds, odds are high that they came from a
supernova in a nearby galaxy. Alternatively, when an astronomer spots
a supernova, scientists at neutrino detectors can look back through
their records to see if they captured a neutrino around that time.
Given that a few supernovae occur in nearby galaxies every year, and
given the sensitivity of neutrino detectors on Earth, they have
determined that at least one of those scenarios -- the two-in-ten-
seconds event or the identification of a supernova neutrino after the
fact -- should be able to happen about once a year. The professionals
need amateur astronomers to help spot new supernovae fast, so
scientists can quickly match captured neutrinos with the exploding
stars that made them. Since 2002, there were at least nine supernovae
identified in galaxies within about 30 million light-years of our
Galaxy, and more than half of those were discovered by amateurs.

Twenty neutrinos were captured in only a few seconds during the
supernova 1987A explosion which occurred in the Large Magellanic
Cloud, so astronomers knew for sure that they came from 1987A, but
since then astronomers have not detected any supernova neutrinos at
all. If we had been identifying one additional supernova neutrino per
year, by now we would have collected a sample as big as that burst in
1987.

Scientists at neutrino detectors could sound an alarm whenever they
detect two particles in ten seconds. Since supernovae emit neutrinos at
the very start of the explosion, the particles would reach Earth hours
before the supernovae would be visible in telescopes, and the
announcement would amount to a supernova forecast.


SIZE OF PLUTO'S MOON
ESO

Astronomers have determined the size and density of Pluto's
satellite Charon by observing a very rare occultation of a star by
Charon from three different sites. The density, 1.71 times that of
water, is indicative of an icy body slightly more than half
composed of rocks. The observations also put strong constraints on
the existence of an atmosphere around Charon.

Since its discovery in 1978, Charon and Pluto have appeared to form a
double planet, rather than a planet-satellite couple; Charon is about
half Pluto's diameter, and about eight times less massive. However,
there have been considerable discussions concerning the precise radii
of Pluto and Charon, as well as about the presence of a tenuous
atmosphere around Charon. In 2004, it was predicted that the
15-magnitude star UCAC2 26257135 should be occulted by Charon on 2005
July 11. The occultation would be observable from some parts of South
America, including the location of ESO's Very Large Telescope.
Stellar occultations have proved to be powerful tools, both to measure
sizes (at km-level accuracy, i.e. a factor ten better than is feasible
with other techniques), and to detect very tenuous atmospheres (at
microbar levels or less).

Unfortunately, in the case of Charon, such occultations are extremely
rare, owing to the very small angular diameter of the satellite on the
sky. That explains why only one occultation by Charon was ever
observed before 2005, namely on 1980 April 7 by Alistair Walker, from
the South African Astronomical Observatory. Similarly, only in 1985,
1988 and 2002 could astronomers observe stellar occultations by Pluto.
Several factors, however, have boosted our odds for witnessing
occultations of Charon. Larger telescopes now give access to fainter
stars, thus multiplying the candidates for occultations. Secondly,
stellar catalogues have become much more precise, allowing us to do
better predictions. Finally, the Pluto-Charon system has recently
entered a Milky-Way star field, thereby increasing the likelihood of
occultations.

Accurate timings of last year's occultation at the three sites show
Charon's radius to be 603.6 km, with an uncertainty of the order of 5
km. The same observations show that if a tenuous atmosphere exists on
Charon, linking it to the freezing -220 C surface, its pressure has to
be less than one tenth of a millionth that at the surface of the
Earth, or 0.1 microbar, on the assumption that it is constituted
entirely of nitrogen. The observations also indicate that methane
ice, if present, should be restricted to particularly cold regions of
the surface. Similarly, nitrogen ice would be confined at best to
high northern latitudes or permanently shadowed regions of Charon.


THIRD STAR IN POLARIS SYSTEM OBSERVED DIRECTLY
The Register

The Hubble telescope has obtained an image of the Polaris star system,
showing directly for the first time the third member that was
previously known only by its gravitational pull on the primary star.
The system, made up of Polaris A, B and Ab, lies around 430 light-years
from Earth, less than one degree from our celestial north pole. It is
an obvious visual double star: Polaris B was first observed by William
Herschel in 1780 and can been seen through small telescopes. The
principal star, Polaris A, is an F-type supergiant and is a Cepheid
(pulsating) variable, showing magnitude and radial-velocity variations
with a periodicity of slightly less than four days; the amplitude of
the variations has decreased during recent decades. In addition to
the velocity variations attributable to the Cepheid-type pulsations,
the star has shown slow changes of radial velocity that demonstrate
that it is one member of as spectroscopic-binary system of long
period. That was announced as long ago as 1899 from the Lick
Observatory, after only three years' measurements had been made. In
1929 an orbit having a period of about 30 years was determined from
more than 700 Lick radial-velocity measurements; it was refined in a
further discussion in 1965 and remains the longest-period orbit
reliably determined from radial-velocity measurements alone. The
nature of the system has therefore been clear for a very long time,
and it has been evident from the known orbit that the angular
separation would not be so small as to be beyond visual resolution by
double-star experts. What has been preventing direct observation of
Polaris B, which is a main-sequence star, has been the great disparity
in brightness between it and the principal star, which is more than
two thousand times brighter than the Sun. It is the large dynamic
range of the Hubble image that has now allowed Polaris B to be
detected directly, less than two-tenths of an arcsecond from the
primary star.


EMBEDDED DWARF GALAXY
New Scientist

Astronomers mapping the Galaxy's stars with the Sloan Digital Sky
Survey -- a project that has so far plotted one-fifth of the night sky
-- have discovered what appears to be a dwarf galaxy embedded within
the Milky Way. Lying 30,000 light-years from Earth, it appears as the
largest galaxy in the sky in angular measure but has a mass not much
more than that of a star cluster. It is believed that the object,
dubbed the Virgo overdensity, is a dwarf galaxy that has fallen prey
to the Milky Way's intense gravity.


FASTEST-SPINNING NEUTRON STAR
New Scientist

The fastest-spinning neutron star found so far has been discovered in
a cluster of 10-billion-year-old stars called Terzan 5, which lies
28,000 light-years away near the centre of the Galaxy. Most pulsars
rotate a few times per second, but some spin hundreds of times faster.
Those so-called millisecond pulsars are thought to rotate so quickly
because they have stripped mass and angular momentum from companion
stars at some point in their past histories. Terzan 5 contains 33 out
of the 150-odd known millisecond pulsars -- the highest number in any
star cluster. The new one is interesting because it rotates 716
times a second, somewhat higher than the previous record. Although
most pulsars should have enough self-gravity to spin as fast as 3000
times per second before they split apart, none so far discovered
approaches that limit. That has led to the belief that they emit
gravitational waves -- theoretical ripples in space-time -- that keep
their spins in check. Massive, fast-spinning objects that are not
perfectly symmetrical are predicted to radiate away energy in such
waves, with faster objects radiating much more energy than slower
ones. Finding the maximum achievable rotation rate could throw light
on a variety of astrophysical problems.


ROCKY RINGS AROUND SUN-LIKE STARS
New Scientist

Discs of rocky material, possibly analogous to the Kuiper Belt in our
own Solar System, have been found around two relatively old, Sun-like
stars. The presence of dusty, rocky discs has been inferred around
more than 100 stars because the stars shine with an unexpectedly high
amount of infrared light -- the infrared excess is from the heat of
the dust itself, which may arise through the star warming the rocks --
but the stars themselves produce so much glare that only a few discs
have been seen at visible wavelengths, which provides information
about their extent and structure.

Now, researchers have used the Hubble telescope to image two dusty
discs around stars 60 light-years from Earth. The work brings the
total number of discs seen at visible wavelengths to nine, including
our Solar System's ring of icy objects beyond Neptune. The known
discs actually look like rings -- their central regions are thought to
be swept clear by planets. One of the newly discovered discs, around
the star HD 53143, is wide, with its belt measuring more than 55 AU
across. The other is 26 AU wide, with an abrupt outer edge 109 AU
from its star HD 139664.


COMET SAMPLE SUCCESS
Reuters

A canister containing particles trapped after the Stardust space
probe's 2004 encounter with Comet Wild-2 has landed on Earth. When
the sample canister inside the capsule was opened, scientists could
see small black rocks and other particles that had been trapped in the
probe's gel-filled collection device. The Stardust spacecraft lifted
off seven years ago and aimed for a close encounter with Comet Wild-2,
a relative newcomer to the comparatively warmer region of space
between the orbits of Mars and Jupiter. The comet is believed to come
from the Kuiper Belt region beyond Neptune, but in 1974 had a close
approach to Jupiter which deflected the icy body into its new orbit.
Because Wild-2 has not been circling near the Sun for long, the comet
is believed to contain most of its original materials.


SPACECRAFT HEADS FOR PLUTO
AP

The New Horizons spacecraft has been successfully launched.
Travelling at speeds reaching 16 km/s it will take 9 1/2 years to
reach Pluto. The 1,054-pound spacecraft is loaded with seven
instruments that will photograph the surfaces of Pluto and its large
moon, Charon, and analyze Pluto's atmosphere. New Horizons also
contains some of the ashes of Clyde Tombaugh, the astronomer who
discovered Pluto in 1930. The spacecraft will be able to use
Jupiter's gravity to shave five years off the trip, allowing it to
arrive as early as July 2015.



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 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 new 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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