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PostPosted: Sun Feb 22, 2009 1:07 am 

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Electronic News Bulletin No. 261 2009 February 15

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
at 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

By Alastair McBeath, SPA Meteor Section Director

Additional data on IYA2009's first major shower has continued to come
through since the preliminary round-up in ENB 259 (at ), including fresh visual data from George
Gliba (West Virginia, USA), who caught a magnitude -3 Quadrantid
at 09:50 UT which was also seen by Rich Taibi in Maryland, plus
automated video results from Enrico Stomeo (Scorze, Italy) for January
3-4, and Ferruccio Zanotti (Ferrara, Italy) for January 2-3. Ferruccio's
results were limited by poor weather early in the night, but he caught
the strongly-rising activity towards dawn very nicely, with up to two or
three Quadrantids per minute at times between 04:50-06:00 UT.
Enrico's data showed a most intriguingly strong Quadrantid video rate
right at the start of the night on January 3-4. Between 16:43-17:44 UT
he caught 5 Quadrantids, which allowing for the low radiant elevation
then was possibly a similar level of real activity to what he caught right
at the end of the previous night! He recorded lower Quadrantid video
numbers through till the hour ending at 19:46 UT, but then nothing more
from the shower till about 22h UT, by when the radiant was reaching a
useful elevation from his location once more.

The radio results have been added to too since ENB 259 thanks to the
arrival of Radio Meteor Observation Bulletin 186 (January 2009; see ), courtesy of Editor and observer Chris Steyaert
in Belgium. The other Quadrantid RMOB radio observers included:
Enric Algeciras (Spain), Orlando Benitez (Canary Islands), Mike
Boschat (Nova Scotia, Canada), Jeff Brower (British Columbia,
Canada, who helpfully provided separately more detailed information
from his January radio data than was featured in the RMOB), Willy
Camps (Belgium), Gaspard De Wilde (Belgium), SPA Assistant
Meteor Director David Entwistle (England), Alex Guzanoff (Oktyabrsky,
Russian Federation), Alfred Krohmal (Syzran, Russian Federation),
Ed Majden (British Columbia, Canada), Mike Otte (Illinois, USA), Ivan
Sergey (Belarus), Andy Smith (England), Dave Swan (England),
Maarten Vanleenhove (Belgium), Felix Verbelen (Belgium) and John
Wardle (England). Discussion of these has continued with Jeff and
David in recent weeks as well, and the following notes reflect this, as
well as my own detailed analysis of all the available radio data
(including the Japanese summary mentioned previously) in the last
few days.

Substantial activity due to the Quadrantids was found in all the viable
datasets on January 3, significantly more obviously than is sometimes
the case, which would fit with the initial International Meteor
Organization's (IMO's) findings of unusually protracted, strong
Quadrantid rates overall. A significant number of radio observers
detected well-above-normal meteor echo counts from 23h UT on
January 2 to 20h UT on January 3, with an especial core period lasting
from roughly 03h to 17h UT on the 3rd. Within that core, there were two
distinct main peak phases, one from roughly 04h to 08h (especially
during the one-hour data collection bin from 06h-07h), the other fairly
consistently from 13h to 15h UT. As far as the results allowed, both
these peak episodes seemed equally strong at their best. The relatively
lowest activity between them was from roughly 08h to 10h UT, but even
that was well above the usual background. There was though no distinct
peak around 18h UT, as was suspected from some of the early radio
results. Although Enrico's video data did suggest some possible
support for this initially, it now seems he was lucky in catching the very
tail-end of the UT afternoon Quadrantid peak, part of the falling activity
seen in the radio analysis till about 20h UT.

The preliminary IMO short-interval visual analysis (off the homepage) has continued to be updated since
ENB 259 as well, suggesting that Zenithal Hourly Rates (ZHRs) of
100+ were present from roughly 04:30 to 18h UT on January 3,
possibly with ZHR peaks of ~115 around 05h-06h, ~130-150 from
09h-12h, and ~160 in the hour centred on 13:00 UT. There remain
some quite substantial gaps in its coverage however, especially
between 06h-09h and 14h-17:30 UT, which the radio analysis has now
indicated may be important for determining how the shower performed
this year.

As always, many thanks and congratulations are due to all the named
observers here and in ENB 259 for their splendid observing efforts, as
well as for their comments, and in some cases detailed discussions.
In particular, the radio analysis this time, so often a difficult and
inconclusive task, has produced an unusually clear pattern, one which
perhaps in time enough visual and other video observations may be
able to confirm (or not!).

By Alastair McBeath, SPA Meteor Section Director

A little more information on last December's Ursids has become
available since the previous notes on the shower in ENB 259. Some
visual data from Robin Gray in Nevada, USA for December 22-23 was
kindly forwarded to us by Rich Taibi, Robin spotting no Ursids the night
after the maximum, helping confirm the previously-established brevity
of the source at an easily-detectable level. Jeff Brower also provided
some additional details from his radio reports made across the
shower, which largely confirmed his earlier findings reported previously.
Sirko Molau's summary of the IMO video reports, chiefly made from
Europe, circulated on the IMO-News e-mail group on January 22,
mentioned locating an Ursid peak probably less active than in either
2006 or 2007 around 02h-03h UT on December 22, but he made no
comment about the peak seen later that UT morning over North
America. The IMO's visual data estimates (see ) suggested ZHRs were no higher
than 10 on December 22, although there were only two adjacent
datapoints showing this, at 00:01 and 10:17 UT, which could suggest
at least an unusually protracted period of better Ursid rates. It is
unclear why the ZHRs were so far below some of the earlier
estimates. For example, variable ZHRs of 15-30 were found from
December 22 results submitted to the SPA during the 00h-03h UT
interval, perhaps rising again to levels of 15-35 around 06h-09h UT
over North America, as noted in ENB 258 at ,
while the radio results suggested peaks around 01h-03h, 07h-08h and
09h-10h UT in ENB 259. The IMO results may have been derived by
combining data from too large a time-span perhaps, thus losing the
significance of some of the detected higher activity in between the two
combined datapoints. My grateful thanks go again to everyone who
has contributed observations and comments from the shower to the

By Alastair McBeath, SPA Meteor Section Director

As part of the SPA's activities during IYA2009, the Meteor Section's
webpages are undergoing a thorough overhaul at present. The first of
the upgraded webpages have just gone "live" online, with other
changes and improvements to follow during the rest of this year. The
new-look homepage remains where it always has been, at , which allows access to
all the other Meteor Section pages.

Probably the single biggest change is that for the very first time, the
Section's instruction booklet "Observing Meteors" which only SPA
members who joined the Section used to receive, is now freely
available complete online. To accompany this, another new page has
been prepared with additional advice for those wishing to try out
meteor imaging, while a further page on radio meteor observing will
be provided soon.

Not everything has or will be changed, of course. The monthly meteor
activity pages will continue to appear regularly, and the Recent Fireball
Sightings page will be updated as fresh information becomes available,
as normal. The annually-updated Meteor Showers List will continue,
and the 2009 to January 2010 version will be online shortly. The
archived reports from previous years will stay as well, but have moved
to a new entry-page. Additions will be made to these with links to
Forum and ENB reports later on. Links to such reports from the current
year are also available via their own separate gateway page. The
Fireball Observing page has been rewritten, and includes a new report
form, available from its usual address, ... htings.htm .


The greenish-looking Comet Lulin, named after the observatory in
Taiwan where the discovery photo was taken, will make its closest
approach to the Earth (0.41 AU) on Feb. 24. Current estimates give
the maximum brightness as 4th or 5th magnitude, which means that dark
skies would be required to see it. No one can say for sure, however,
because this appears to be Lulin's first visit to the inner Solar
System and its first exposure to intense sunlight. Lulin's green
colour comes from the gases that make up its Jupiter-sized atmosphere.
Jets from the comet's nucleus contain cyanogen (CN -- observed in many
comets) and diatomic carbon (C2); both substances glow green when
illuminated by sunlight in the near-vacuum of space. The comet rises
a few hours before the Sun and will be at about 30 degrees altitude in
the southern sky before dawn. It may be easiest to find on Feb. 16,
when it passes near Spica, and on Feb. 24, when it will be just a few
degrees from Saturn in the constellation Leo.


Interferometry employing multiple telescopes can determine the sizes
and shapes of asteroids that are too small or too far away to be
resolved by other techniques, and may increase by a large factor the
number of asteroids that can be measured. Direct imaging with adaptive
optics on the largest ground-based telescopes such as the Very Large
Telescope (VLT) in Chile, space telescopes, or radar measurements are
the currently used methods of asteroid measurement. However, direct
imaging, even with adaptive optics, is generally limited to the
largest asteroids of the main belt, while radar measurements are
mostly limited to observations of near-Earth asteroids that have close
encounters with our planet.

In recent experiments with the VLT interferometer, the light from two
of the 8.2-metre 'unit telescopes' was combined, affording a resolving
power equivalent to that of a telescope having an aperture equal to
the separation between the two telescopes used, in this case 47
metres. In principle the interferometer ought to be able to resolve
asteroids as small as about 15 km in diameter in the main asteroid
belt, 200 million kilometres away. In the only actual result so far
reported, the researchers observed the main-belt asteroid (234)
Barbara, which was earlier found to have rather unusual properties.
The observations indicated that that object has indeed a peculiar
shape. The best model (still only tentative) suggests that the
asteroid consists of two bodies with diameters of 37 and 21 km,
separated by at least 24 km.

Cassini Imaging Laboratory

Saturn's largest satellite, Titan, is the only satellite in the Solar
System with a thick atmosphere in which complex chemistry occurs. For
several years, Cassini scientists have suspected that dark areas near
Titan's poles might be liquid-filled lakes. Recent pictures of the
south-polar region show new lake features that were not seen in images
taken a year ago of the same area. The fact that extensive cloud
systems covered the area in the intervening year suggests that the new
lakes could be the result of a heavy rain of hydrocarbons, and that
lakes may owe their presence, size and distribution across Titan's
surface to the moon's weather and changing seasons. Cassini has now
surveyed nearly all of Titan's surface at high resolution. The
observations suggest that there is more liquid methane in the northern
hemisphere than in the southern. Cassini scientists think that, as
the northern hemisphere moves toward summer, large convective cloud
systems will form there, and precipitation greater than that inferred
in the south could extend the northern lakes.

Some of the north-polar lakes are large. If full, Kraken Mare, at
400,000 square kilometres, would be almost five times the size of
North America's Lake Superior. The north-polar dark 'lake' areas
observed by Cassini total more than 510,000 square kilometres --
almost 40% larger than the Earth's largest lake, the Caspian Sea.
However, it does not seem likely that evaporation from the lakes could
be enough to replenish the methane lost from the atmosphere by
rainfall and by the formation and eventual deposition on the surface
of methane-derived haze particles. Combined with previous analyses,
the observations suggest that underground methane reservoirs must

Subaru Telescope facility

Approximately 6,000 light-years away in the constellation Cassiopeia,
there is a very active and massive star-forming region called W3 Main.
Recently a team of Japanese and Indian astronomers has been using the
Subaru telescope in Hawaii to look for dim low-mass stars, and has
found a considerable number of brown dwarfs in the W3 Main region.
That result is significantly different from the one obtained in the
cases of the Trapezium and IC 348, where the relative number of brown
dwarfs is fewer.

BBC News

The smallest exo-planet yet found has been detected by the French
space telescope Corot. The object is less than twice the size of the
Earth and is one of only a few planets so far found with masses
comparable with that of the Earth. About 330 exo-planets have been
discovered so far, but most of them are gas giants similar to Jupiter
or Neptune. The new find, Corot-Exo-7b, orbits a Sun-like star once
every 20 hours and has a temperature between 1,000 and 1,500C.

The vast majority of exo-planets has been discovered by the radial-
velocity method, which was initially developed by the person who edits
these Bulletins. That method favours the detection of large planets
orbiting close to their parent stars. The new planet was detected
photometrically by the transit method, as it crossed the face of the
star, blocking a small fraction of the star's light as it passed in
front. The transit method, too, favours the detection of big planets,
because they block out more light from the parent star, but in a case
-- such as this one -- of a small star then a moderate-sized planet
can be enough to block out enough light for the dimming to be


The Swift and Fermi spacecraft are monitoring a neutron star, 30,000
light-years from the Earth, that is drawing attention to itself with a
series of powerful gamma-ray flares. At times, that remarkable object
has erupted with more than a hundred flares in as little as 20
minutes; the most intense flares emitted more total energy than the
Sun does in 20 years. The star, known as SGR J1550-5418, lies in the
southern constellation Norma. It began a series of modest eruptions
on 2008 Oct. 3, settled down for a while, then had an intense episode
on 2009 Jan 29. Because of its rapid outbursts and gamma-ray
spectrum, astronomers classify the object as a 'soft-gamma-ray
repeater' -- only the sixth known. In 2004, a giant flare from
another soft-gamma-ray repeater was so intense that it ionized the
Earth's upper atmosphere from 50,000 light-years away!

Using data from an X-ray telescope on Swift, astronomers saw the first
'light echoes' to have been observed from a soft-gamma-ray repeater.
Images acquired when the latest flaring episode began show what appear
to be expanding haloes around the source. Multiple rings form as
X-rays interact with dust clouds at different distances. Scientists
think the source of the flares is a spinning 'magnetar', a neutron
star with an incredibly intense magnetic field. One theory of soft-
gamma-ray repeaters holds that the flares are caused by 'starquakes'
in the outer rigid crust of the magnetar. As a magnetar's colossal
magnetic field shifts, it strains the crust with enormous magnetic
forces, often breaking it. When the crust snaps, it vibrates with
seismic waves as in an earthquake and emits a flash of gamma-rays.

Science Daily

Galaxies, such as our own Milky Way, contain billions of stars.
Theoreticians would like to know how such gigantic systems came into
being -- did the central region form first and then grow, or did the
stars form at the same time throughout the entire galaxy? An
international team led by the Max Planck Institute for Astronomy is
now a bit closer to the answer to those questions. The researchers
studied one of the most distant known galaxies, a quasar with the
designation J1148+5251. Light from it has taken 12.8 billion years to
reach the Earth, so the observations show the galaxy as it was all
that time ago, providing a glimpse of the very early stages of
galactic evolution, less than a billion years after the Big Bang.

With the IRAM interferometer, a German/French/Spanish radio telescope,
the observers recorded the infrared radiation emitted by J1148+5251 at
a specific frequency associated with ionized carbon atoms, which is a
reliable indicator of ongoing star formation. The resulting images
show sufficient detail to allow, for the first time, the measurement
of the size of a very early star-forming region. The researchers
concluded that, at that time, stars were forming in the core region of
J1148+5251 at record rates. Every year, that galaxy's central region
produced new stars with a combined mass of more than a thousand Suns.
By contrast, the rate of star formation within our own galaxy, the
Milky Way, is roughly one solar mass per year.

It has been known for some time that young galaxies can produce
impressive amounts of new stars, but overall activity is only part of
the picture. Without knowing the star-forming region's size, it is
impossible to compare star formation in early galaxies with
theoretical models, or with star-forming regions in our own galaxy.
With a diameter of only 4000 light-years (for comparison, the Milky
Way galaxy's overall diameter is something like 100,000 light-years),
the star-forming core of J1148+5251 is extremely productive. In fact,
it is close to the limit imposed by physical laws. Stars are formed
when cosmic clouds of gas and dust collapse under their own gravity.
As they collapse, temperatures rise, and internal pressure starts to
build up. Once that pressure has reached certain levels, all further
collapse is brought to a halt, and no additional stars can form. The
result is an upper limit on how many stars can form in a given volume
of space in a given period of time. Remarkably, the star-forming core
of J1148+5251 appears to be operating at that absolute limit.

Bulletin compiled by Clive Down

(c) 2009 the Society for Popular Astronomy

The Society for Popular Astronomy has been helping beginners to
amateur astronomy -- and more experienced observers -- for more than
50 years. If you are not a member then you may be missing something.
Membership rates are extremely reasonable, starting at just £16 a year
in the UK. You will receive our bright quarterly magazine Popular
Astronomy, regular printed News Circulars, help and advice in pursuing
your hobby, the chance to hear top astronomers at our regular
meetings, and other benefits. The best news is that you can join
online right now with a credit card or debit card at our lively

Kevin Brown, SPA webmaster
My astro blogs.. | Practical Astronomy magazine

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