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The SOCIETY for POPULAR ASTRONOMY
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Electronic News Bulletin No. 191 2006 February 19
====================================================


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/maaevGSabop4xcixLLVb/

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.


TAURID 'SWARM' RETURN FROM 2005
By Alastair McBeath, SPA Meteor Section Director

Analyses of Taurid activity in October-November last year have been
carried out in recent weeks by myself, using results sent to the Section
directly, including data extracted from American Meteor Society (see:
http://popastro.c.topica.com/maaevGSabop4ycixLLVb/ and Arbeitskreis
Meteore
(http://www.meteoros.de) publications, plus all the preliminary visual
data
available online from the International Meteor Organization's Visual
Meteor Database (at: http://popastro.c.topica.com/maaevGSabop4zcixLLVb/
by mid January. From these, it
looks as if the main phase of the 2005 Taurid 'swarm' return ran from
about October 29 to November 10. Combined Zenithal Hourly Rates
from both the Northern (NTA) and Southern (STA) Taurid stream
branches were around 10-15 at best for most of that time, about the kind
of level we would expect only during the normal November 5-12
maximum. There was an unfortunate gap with no visual meteor watches at
all for November 3 or 4, badly timed, as this was about the middle of
the
apparent 'swarm' spell. The NASA-detected November 7 lunar impact
(see ENB 188) thus occurred towards the end of the identified 'swarm'
return.

Attempts to analyze the STA and NTA separately were hampered by
many observers being unable to separate the two sources visually, making
for rather patchy coverage, hence the decision to combine all the
available
data. There were indications the STA may have been dominant during the
'swarm' return however, and indeed throughout the October-November
Taurid epoch generally, including in video data from Steve Evans
(England) and Enrico Stomeo (Italy). The STA also seemed brighter on
average than their Northern counterparts - corrected mean magnitudes
from the IMO data were +2.05 (286 STA meteors) and +2.29 (220
NTA meteors). The significance of this was less clear though, as there
were 262 unidentified "Taurid" meteors as well, which gave a corrected
mean magnitude of +2.09. Splitting these general "Taurids" evenly
between the STA and NTA distributions reduced the apparent difference
in mean magnitudes by about 40%, though the STA remained the brighter.

Fireball reports from the October-November epoch, albeit no specific
source could be identified for many, showed a profile almost the same as
the visual combined Taurid 'swarm' rates through to November 14,
suggesting while not all the fireballs will have been Taurids, most
probably
were. Several dates, including October 30 and 31, and November 2, 5, 6
and 9 saw more than ten fireballs observed from Europe and North
America combined, the most productive date being November 6, when
22 fireballs were spotted.

Although the radio results from the Radio Meteor Observation Bulletins
(available at: http://popastro.c.topica.com/maaevGSabop4AcixLLVb/
demonstrated the typical minor peaks
found since the mid-1990s during the same interval, several of these
were
somewhat more pronounced than seen before, particularly around
November 2, 3 and 7, with an apparently increased overall level after
the
Orionids had faded away in late October. This was similar to what was
found by the radio data during the last autumnal Taurid 'swarm' return,
in
1998, though the pattern overall was not so obviously demonstrated in
2006. Interestingly, the spell of pronounced Taurid fireballs was not
detected at all by the one set of very long-duration radio counts
available
(echoes lasting more than 20 secs), presented by Sadao Okamoto in
Japan. However, both the near-maximum epochs from the Orionids and
Leonids were. This nicely confirmed that such very long-duration echoes
need considerable excess ionization, which in turn seems to require high
velocity bright meteors to generate, as occur from the Orionids and
Leonids at times. They do not simply relate to the presence of bright or
very bright meteors, as some radio observers have suggested in the past.


QUADRANTIDS 2006 - UPDATE
By Alastair McBeath, SPA Meteor Section Director

Radio observations from around the expected Quadrantid maximum in
Radio Meteor Observation Bulletin 150 for January 2006 (see:
http://popastro.c.topica.com/maaevGSabop4AcixLLVb/ have been analysed by
myself in recent days,
further to the preliminary shower news in ENB 189. The contributing
observers included: Enric Fraile Algeciras (Spain), Mike Boschat (Nova
Scotia, Canada), Jeff Brower (British Columbia, Canada), Gaspard De
Wilde (Belgium), David Entwistle (England), Patrice Guerin (France),
Szabolcs Kiss (Hungary), Peter Knol (Netherlands), Stan Nelson (New
Mexico, USA), Sadao Okamoto (Japan), Mike Otte (Illinois, USA),
Andy Smith (England), Dave Swan (England), Istvan Tepliczky (Hungary)
and Felix Verbelen (Belgium).

Enhanced counts were recorded by at least some of the viable datasets
between 00h UT on January 3 to 11h UT on January 4, much of which
probably resulted from the Quadrantids. Within that interval, three
identifiable peaks were found, which seemed significant.

1) An enhancement recorded primarily by most of the European
observers, plus one of the three North American systems, between
~12h-16h UT on January 3, with a probable peak at 14h +/- 1 hour UT.
This was centred soon after one of the radiant's daily best-detectable
times from Europe, and during one over North America, so may be an
artefact of the data rather than a "genuine" meteor activity peak.

2) A peak for the three main geographic regions reporting, Japan, North
America and Europe. It was recorded especially strongly from North
America, and occurred between ~19h-22h UT on January 3. It was
probably at its best around 20h +/- 1 hour UT, and it likely represents
the
main Quadrantid maximum time, because it was found even in a minority
of the European data, despite the very low radiant for observers there
then. There was no evidence to suggest anything unusual occurred around
the predicted ~18h30m UT maximum timing, so it seems possible the true
Quadrantid peak was a little later than usual in 2006.

3) A peak found in all three geographic areas again (albeit weakly in
Japan), but most strongly from Europe, between ~03h-07h UT on
January 4. It was best-detected around 05h +/- 1 hour UT. The
European systems had another of their best-detectable times for the
Quadrantids about this period, but there was one North American
detection too, from the worst time of day for observations there, which
raised its potential significance. A peak at ~05h UT would be roughly 9
hours after the 20h UT main maximum, which would seem in-line with
what some visual and, especially, the radio data in several recent years
have shown; a potential secondary Quadrantid maximum trailing the main
one by about 9-12 hours.

Other fresh Quadrantid results since ENB 189 included a visual report
from Pam Foster in Perthshire, and video data from Enrico Stomeo in
Italy. Enrico's video counts, corrected for the variable Quadrantid
radiant
elevation, seemed to suggest peaks on January 3/4 around 19h-21h (the
marginally strongest, but based on extremely low detected Quadrantid
numbers), 00h-01h, and 02h-05h UT. The first and third of these are
interesting, given the radio findings, while oddly, three European radio
stations (of the eight viably active) suggested a possible weak maximum
in
the 01h UT bin as well. There was a possibility in the few visual
reports
received by the Section near this time, that Zenithal Hourly Rates were
also somewhat increased in the hour or so centred at approximately 01h
UT. This would need more data to confirm however, which given the
poor skies across much of Europe on the critical night, seems unlikely,
regrettably.


JANUARY 11-12 FIREBALL UPDATE
By Alastair McBeath, SPA Meteor Section Director

A detailed analysis of this magnitude -9/-13 event, which occurred at
22:41:00 +/- 10 secs on January 11 over eastern England, has been
prepared this week, after follow-up enquiries to the seven observers
(scattered from near Blackpool on the Lancashire coast, south via
Shropshire and the West Midlands to Luton, Buckinghamshire and
Essex) were completed. Unfortunately, but as sometimes happens when
only visual data are available, the reports did not all fit to a single
straightforward solution. The start was very poorly-seen, a common
problem, as this is typically the faintest part of any meteor's trail.
It might
have been nearly anywhere above western Hampshire, Sussex, Surrey,
London, north-west Kent, Essex or southern Suffolk, or even the North
Sea offshore of the Thames estuary, but five of the seven reports
favoured
the more westerly end of this zone, suggesting a possible start in a
rough
circle of about 45 km radius centred near Leith Hill in Surrey. However,
a
start towards the eastern limit, over southern or eastern Essex to the
adjacent North Sea or south Suffolk, in a similarly-sized area centred
over the sea about 10 km south-east of Mersea Island, Essex, could not
be excluded. The meteor also seems to have begun at an unusually high
altitude, perhaps around 150 +/- 10 km (most meteor ablation occurs
between 90-120 km altitude, but larger, faster objects can begin
"burning-
up" higher than this). The end of the visible trail was probably
somewhere
in a roughly circular area about 75 km in diameter, centred near
Grantham in Lincolnshire, at ~50 +/- 10 km altitude.

While far from ideally-established, but assuming these details to be
roughly correct, the two start regions would have meant the trend of the
meteor's trajectory was generally either SSE-NNW or SE-NW, with a
mean visible path length of ~240 km to ~180 km, descending at an angle
from the horizontal of between 22 to 33 degrees (variable within these
limits, depending on the start and end heights and path lengths
involved).
The large uncertainties in these parameters suggested an equally large
possible atmospheric velocity range, based on the majority consensus
full-
duration estimates for the visible trail, of around 3 to 5 seconds.
These
would solve for a range probably from 50 to 65 km/sec, but possibly
outside this, from maybe 35 km/sec to the upper limit for natural meteor
velocities near the Earth, 72 km/sec. The potential start height would
tend
to favour a higher velocity object.

No comments about sonic booms associated with this event were
received, which with the relatively high end height (many meteoritic
fireballs tend to remain visible to under 20-30 km altitude) and
possible
high velocity, would tend to count against the likelihood of meteorites.
Extrapolating from the main possible trajectories could have produced a
potential meteorite fall zone across much of northern England - nearly
anywhere in Yorkshire, Lancashire, Cumbria, or even the adjacent North
or Irish Seas, north of about Sheffield - far too great an area to
search,
given the large uncertainties about the fireball's flight. No reports of
possible meteorite falls have been received from this area since the
event.

Unless any fresh data, particularly images of the fireball, become
known,
this rather vague review is probably as accurate as practical. If anyone
is
aware of further observations of this, or any other bright meteors (a
fireball is any meteor that reaches magnitude -3 or brighter with
respect to
the stars and planets), advice on what to report and where to can be
found via the "Fireball Observing" page off the meteor homepage at:
http://popastro.c.topica.com/maaevGSabop4BcixLLVb/ .


JANUARY 21-22 FIREBALL
By Alastair McBeath, SPA Meteor Section Director

Another bright fireball, of about magnitude -6/-8, was spotted from two
sites in Hampshire and Swansea, around 20:55-21:00 UT on January 21.
This looks to have been quite distant to Britain, perhaps over the Bay
of
Biscay or the eastern Atlantic off Brittany, but additional sightings
would
be needed to pin it down more closely.


COMET TEMPEL 1 HAS SURFACE ICE
Science

NASA scientists say that the 'Deep Impact' space probe that collided
with Comet Tempel 1 on July 4 found evidence that the comet has got
ice on its dusty surface. Researchers analyzing data recorded by the
probe's mother ship concluded that the comet has three small pockets
of thin ice that cover one hundredth of a square mile out of the
comet's total surface of 45 square miles. About 6 per cent of the ice
is pure, while the rest is mixed with dust.


FAINTEST ANDROMEDA SATELLITE GALAXY
New Scientist

The faintest satellite galaxy yet found around the Andromeda Nebula
has been turned up by the Sloan Digital Sky Survey. No doubt other
dim galaxies remain undetected. Certain theories would like there to
be about 100 times more dwarf galaxies than are actually observed -- a
discrepancy known as the missing-satellite problem -- and astronomers
have been scrabbling around trying to explain the difference. But in
the last two years astronomers have discovered two particularly faint
galaxies -- UMaj around our Milky Way and Andromeda IX around our
nearest large galactic neighbour, Andromeda. Those finds suggest
that the missing-satellite problem may actually be less dire than
originally thought. The new discovery is called Andromeda X and is
the faintest known satellite of Andromeda. It appears to lie about
280,000 to 450,000 light-years from Andromeda, which itself lies 2.5
million light-years from us. All three of the new finds have been
made from the Sloan Digital Sky Survey, which is systematically
mapping one-quarter of the sky.


DARK MATTER IS WARM
BBC News

Some astronomers at the Institute of Astronomy in Cambridge think that
they have been able to quantify for the first time certain physical
characteristics of dark matter. There is gravitational evidence that
galaxies contain a great deal more mass than can reasonably be
assigned to the sorts of objects that they are seen to contain. Now,
limits have been placed on how it is packed in space, and its apparent
temperature has been estimated, by a study of 12 dwarf galaxies that
skirt the edge of our own Milky Way. Using the Very Large Telescope
in Chile and other telescopes, the researchers have made 3D maps of
the galaxies, using the movements of their stars to try to trace the
impression of the dark matter among them and to determine its mass.
They find that the galaxies contain about 400 times as much dark
matter as normal matter.

It comes in a 'magic volume' which corresponds to an amount 30 million
times the mass of the Sun. It looks as if that amount is never packed
into a volume less than about 1,000 light-years across. That
corresponds to a speed (about 9km/s) at which the dark-matter
particles must be supposed to be moving, because at that speed they
are moving too fast to be compressed into a smaller volume. Those are
the first properties of the matter, other than its mere existence, to
have been determined. The speed is a surprise, because theory had
proposed that dark-matter particles would be extremely cold, moving
at a few millimetres per second, but the new observations indicate
that they are quite warm (in cosmic terms) at 10,000 degrees.
Astronomers and others are still speculating on the actual nature of
the dark matter.

The Cambridge efforts have produced an additional, independent result:
the study of the dwarf galaxies has allowed the scientists to make a
new estimate of the mass of our own galaxy. "It turns out the Milky
Way is more massive than we thought", said team leader Professor
Gilmore. "It now looks as though the Milky Way is the biggest galaxy
in the local Universe, bigger even than Andromeda. It was thought
until just a few months ago that it was the other way round."


GLOBULAR CLUSTER MAY HAVE LOST A MILLION STARS
ESO

Italian astronomers report that the globular cluster Messier 12 must
have lost to our Milky Way galaxy close to one million low-mass stars.
The team measured the brightnesses and colours of more than 16,000
stars within the cluster with the VLT at Cerro Paranal (Chile).
Located at a distance of 23,000 light-years in the constellation
Ophiuchus, M12 contains about 200,000 stars, most of them having
masses between 20 and 80 per cent of the mass of the Sun. The
astronomers claim that the cluster is surprisingly devoid of low-mass
stars, because for each solar-like star, they would expect roughly
four times as many stars with half that mass. Observations show only
an equal number of stars of different masses.

Globular clusters move in extended elliptical orbits that periodically
take them through the densely populated region of our Galaxy (the
plane), then high above and below, in the halo. Gravitational effects
analogous to tides on the Earth are strong enough in the innermost and
densest regions of the Milky Way, the 'bulge', to overcome the
relatively feeble gravity of a star cluster and cause low-mass stars
to 'evaporate' and be lost from the cluster permanently. The research
estimates that M12 has lost four times as many stars as it still has
-- that is, roughly one million stars must have been mixed into the
halo of our Milky Way. The total remaining lifetime of Messier 12 is
predicted to be about 4.5 billion years, i.e. about a third of its
present age. That is short compared to the typical globular cluster's
expected lifetime, which is about 20 billion years.


SATURN'S INNER MOONS
New Scientist

A team of Cassini scientists suggests that Saturn's small inner moons
may not be chunks of ice as once thought, but rather accretions of
material built up around small central cores. Cassini has sent images
of those satellites, and scientists have examined the moons' shapes,
estimated their masses and calculated their densities. The 'rounded
football' shape of Calypso, Telesto, Epimetheus, Janus, Pandora,
Prometheus, Atlas and Pan is characteristic of accreted bodies, whose
material has built up around a core. That means that the moons are
"almost undoubtedly rubble piles" formed through accretion.
Scientists still have not got reliable masses for two of the so-called
Trojan moons of Saturn -- Telesto and Calypso -- but the team includes
them on the basis of their shapes as satellites likely to have been
accreted. The very low densities, between about 0.4 and 0.6,
calculated for the moons with known masses further support the
'rubble-pile' theory.


COUNTER-ROTATING DISC
NRAO

Astronomers using the VLA radio telescope have studied motions within
a disc of material that is orbiting a still-forming star some 500
light-years from Earth in the direction of Ophiuchus, and have found a
curious result -- the inner part of the disc seems to be orbiting the
proto-star in the opposite direction from the outer part. Any
planetary system that forms around the star will therefore presumably
include planets orbiting in different directions, unlike our own Solar
System in which all the planets orbit the Sun in the same direction.
The system may have acquired material from two clouds of pre-stellar
material instead of the usual single one. It is in a large star-
forming region where chaotic motions and eddies in the gas and dust
result in smaller cloudlets that could rotate in different directions.
Though this is the first time such a phenomenon has been seen in a
disc around a young star, it has previously been reported in the discs
of certain galaxies.


METAL-RICH DISTANT GALAXY
ESO

Astronomers have found a metal-rich hydrogen cloud in the distant
Universe by studying absorption lines superimposed, by an otherwise
invisible galaxy 6.3 billion light-years away, upon the light emitted
by a quasar located far behind it in the same line of sight. The team
studied the spectrum of the quasar SDSS J1323-0021 that shows clear
indications of absorption by a cloud of hydrogen and metals located
between the quasar and us. From an analysis of the spectrum, the
astronomers found the galaxy to be four times richer in zinc than the
Sun. Other metals such as iron appear to have condensed into dust
grains.


SPAIN TO JOIN ESO
ESO

Following approval by the Spanish Council of Ministers and the
ratification by the Spanish Parliament of the ESO Convention and the
associated protocols, Spain intends to become ESO's 12th member state
on 2006 July 1. Spain is an important member of the European
astronomical community and is host to the Observatorio del Roque de
los Muchachos on La Palma and the Spanish 10m GranTeCan telescope
now nearing completion.


ROTATING RADIO TRANSIENTS
The Register

Astronomers at Jodrell Bank have discovered a new type of star,
Rotating Radio Transients (RRATs). A survey of the Milky Way for
pulsars, with the Parkes radio telescope in Australia, revealed 11
sources of very short radio flashes, each around one hundredth of a
second long and typically separated by three or four hours. The time
a RRAT may be visible to telescopes is tiny, a total of something like
a tenth of a second per day. It is thought that RRATs, like pulsars,
are a form of rotating neutron star. Whereas radio signals from
pulsars have a regular period concurrent with their rotation, the
RRATs at first seemed to pulse at random. Further investigation
showed that the long silences were always multiples of a shorter time,
which the researchers believe to be the period of the RRAT's rotation.
The period of more than half the known RRATs is over four seconds,
much longer than for the vast majority of known pulsars. However, the
four-second period is similar to that of 'magnetars', which emit only
X-rays or gamma radiation. Astronomers speculate that RRATs may
represent an evolutionary stage of neutron stars to or from magnetars
and that the new stellar class probably outnumbers pulsars.


PHILIP'S RECENT 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 - £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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