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The SOCIETY for POPULAR ASTRONOMY
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Electronic News Bulletin No. 230 2007 October 28
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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 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
visiting http://popastro.c.topica.com/maaiszzabCiamcixLLVb/


ORIONIDS - FIRST NEWS
By Alastair McBeath, SPA Meteor Section Director

As hoped for in ENB 229, enhanced Orionid activity did happen again
this year, with elevated Zenithal Hourly Rates (ZHRs) reported from
several nights across the expected peak on October 21. Data are still
coming through, so this is only a very preliminary assessment, but
initial
SPA data coupled with the ZHR estimates from the International
Meteor Organization's "live" Orionid results (available off the
http://popastro.c.topica.com/maaiszzabCiancixLLVb/ homepage) suggest at
best on October 21-22,
ZHRs may have been around 50-70 for most of the night over Europe.
Activity was better than normal from at least October 19-23 (ZHRs of
20+ seen on all nights) too, though early indications are that the best
rates were not sustained beyond October 21-22, unlike in 2006.
Another difference to last year's strong return with many bright meteors
was that the magnitude distribution was quite normal, or perhaps even
a little fainter than normal. Very few negative magnitude Orionids, and
no fireballs, have yet been reported to the Section from full meteor
watch observations, for instance, which is unusual. An analysis of the
few complete visual datasets to come through to us so far, suggested
mean magnitudes corrected to a limiting magnitude +6.5 sky of +2.8
for the Orionids and +3.4 for the sporadics, the Orionid value rather
below average.

Observers providing at least some detailed information about the shower
and its rates so far were: Mike Alexander (Galloway), Walter Bradford
(Co. Durham), Mike Clarke (unstated location), "Col Man" (Leeds),
Assistant Meteor Director David Entwistle (Lancashire), Dave Hancox
(East Ayrshire), "Martinastro78" (Co. Derry), SPA Comet Director
Jonathan Shanklin (Cambridgeshire), Richard Taibi (Maryland, USA),
and the Director (Northumberland). This includes contributors to the
Orionid topics on the SPA's Observing Forum at:
http://popastro.c.topica.com/maaiszzabCiaocixLLVb/ and on the UK
Weather World's Space
Weather Forum at: http://popastro.c.topica.com/maaiszzabCiapcixLLVb/

In the UK, a persistent high pressure area meant several nights in the
week leading up to the maximum provided some people with an
opportunity to check for Orionids. Rates were generally normal (so
relatively low, ZHRs less than 10) in what was reported up to October
17-18, but an unfortunate gap on October 18-19 may have given the
obviously better rates on October 19-20 undue prominence, as the
activity seemed to have jumped up to nearly normal maximum levels by
then, well ahead of the peak. For British observers, October 20-21
seems to have been the last better night, after which fog and low cloud
set in for most people, but those who took advantage of the post-
moonset hours then were not disappointed, with sometimes three or
four Orionids a minute (but also up to ten-minute gaps with no meteors,
so not quite so enticing a prospect as this may seem!). ZHRs then in
SPA data averaged 40-50, about twice the usual maximum quantity of
20-25, and most of those to have covered the Orionids before were
impressed by what they saw that night particularly. Rates still seem to
have been elevated above usual towards dawn on October 22-23 in
the limited results available then (hindered by a late moonset), but
sadly
there are so far no British reports from October 21-22 at all.

Many thanks go to everyone who has already sent in a report on how
their efforts went. All further Orionid results would be most welcome,
especially full meteor watch data to help refine these first estimates.
Details of what to send and where to can be found on the Section's
webpages off the Meteor homepage:
http://popastro.c.topica.com/maaiszzabCiaqcixLLVb/ .


RECENT FIREBALLS
By Alastair McBeath, SPA Meteor Section Director

Since the last ENB was prepared, news has come through of a major
bolide over Finland on September 28, around 18:39 UT, which was
probably in the magnitude -17/-20 range or brighter. It seems possible
a meteorite fall has resulted, but there were problems in analysing the
300+ witness reports, which did not initially produce an accurate
enough atmospheric trajectory. With the first winter snows already
down in Finland, the chance of finding any surviving pieces has
decreased. There are some details (in Finnish only last time I checked)
at: http://popastro.c.topica.com/maaiszzabCiarcixLLVb/ , and further
notes have been posted on the
Meteorobs bulletin board in English too. You can get to Meteorobs
via the link on the SPA site at:
http://popastro.c.topica.com/maaiszzabCiascixLLVb/ .

From Britain, among other sightings recently, two events have been of
particular interest. Witnesses at six sites so far have reported on a
magnitude -5/-8 meteor that happened around 18:22 UT on October
5-6. The observers were in Cheshire, the West Midlands, Essex,
Somerset, Surrey and Kent. Unfortunately, few accurate sky-positions
on it were secured, and a best estimate can only hint that it may have
passed high over central and eastern England, possibly on a roughly
NW to SE track. As it happened while the sky was still twilight, the
magnitude may be an under-estimate.

The second fireball was in daylight on October 17, around 13:40 UT,
as seen from Somerset and Powys. One of the sightings and some other
notes can be found at:
http://popastro.c.topica.com/maaiszzabCiatcixLLVb/ on the UK Weather
World's Space Weather Forum. Very few details are available as yet,
but the Powys observer saw the fireball to the east, so it may have
been somewhere high above central-eastern southern England.

Any further reports of these or other fireballs (a fireball is any
meteor
that reaches at least magnitude -3) would be welcomed by the SPA.
Please see http://popastro.c.topica.com/maaiszzabCiaucixLLVb/ for
information on what to report and
where to.


METEOR PROSPECTS FOR NOVEMBER
By Alastair McBeath, SPA Meteor Section Director

First-up for meteor maxima in November is expected to be the
splendidly moonless pair of minor Taurid peaks around November 5
(Southern Taurids) and 12 (Northern Taurids), though the combined
effect of both showers is to produce an almost plateau-like maximum
between these dates, with combined ZHRs of ~8-10 or so. No
increased rates or better than normal fireball activity is due from them
till the next Taurid "swarm" return in 2008, last seen so impressively
from late October to mid November in 2005 - but you never know!

Leonid rates could be fairly normal this year at their "usual" peak, due
on November 17-18 towards 03h UT, with ZHRs of maybe ~15.
However, it is possible elevated activity may happen for several days
around this, perhaps from November 17 to 19, due to a complex series
of Leonid meteoroid trails which will lie scattered near the Earth's
orbit
this time. A stronger maximum may occur within a couple of hours of
midnight UT on November 18-19, which could consist of many small
meteoroids (so producing a lot of faint meteors). Potential ZHRs
according to one suggestion may be ~30. If many faint meteors are
present though, very dark, clear skies will be needed to see them. The
waxing Moon, at first quarter on November 17, will set around midnight
UT even by November 18-19 for the UK, while the shower's radiant
rises only by ~23h UT, and reaches a fully usable elevation after
midnight, so dark skies should prevail for whatever entertainment the
swift-moving Leonid meteors provide. Other unexpected peaks are not
ruled out by any of these predictions, so observers trying to catch
whatever takes place should be alert from about radiant-rise/moonset
onwards (whichever is the later) on any clearer nights from at least
November 17-20, and hope for the best!

The swift-meteor Alpha Monocerotids are usually a minor shower, with
a maximum due this year at ~03h10m UT on November 21-22. In
most years, their peak ZHR is around 5, but very occasionally, a much
stronger outburst happens, when for a short while, their ZHR rises
dramatically into the hundreds. The most recent such event was in
1995 November. Unfortunately, we are not certain just what the repeat
interval is for such events, so observations of the shower are needed in
all years, whenever the weather permits. This year, the peak timing is
perfect for Britain, as the radiant is well on-view only after 23h UT or
so, but the nearly full Moon will set only after 04h30m-05h00m UT on
November 22, making checking across the key peak time tricky. If
skies allow, watchers then should face away from the Moon, but still
looking at as much sky as comfortably possible, with fingers crossed!

More information on these and other showers active in November,
including radiant charts for all three of those here, can be found among
the SPA's Meteor webpages, at:
http://popastro.c.topica.com/maaiszzabCiavcixLLVb/ . Good
luck, and clear skies!


SOLAR STORM RIPS TAIL FROM COMET
The Register

STEREO, NASA's satellite deputed to examine the surface of the Sun,
has returned images of a collision between a comet and a solar
'hurricane'. The force of the solar storm, a 'coronal mass ejection',
was so great that it tore the plasma tail from the comet. In a
sequence of four images, the tail of Encke's Comet can clearly be seen
to brighten as the cloud of highly-charged solar material sweeps past.
The comet's plasma tail is then detached and carried away by the
ejected solar mass.


HST IMAGES EXTREME STAR CLUSTER
STSI

The Hubble telescope has taken a picture of NGC 3603, a nebula first
recorded by Sir John Herschel in 1834, which lies in a prominent
star-forming region in the Carina spiral arm of the Milky Way, about
20,000 light-years away. The picture shows a young star cluster
surrounded by dust and gas. Most of the bright stars in the image are
hot blue stars whose ultraviolet radiation and violent winds have
blown out an enormous cavity in the gas and dust enveloping the
cluster. The image provides a snapshot in time of many stars with
differing masses but similar ages in the young cluster. That
allows detailed analysis of several types of stars at varying stages
in their lives; astronomers can compare clusters of different ages
with one another and determine how the properties (such as temperature
and brightness) of stars change as they get older.

The cluster appears to gather the most massive stars at its core, and
the distribution of different types of stars at the centre of this
very dense cluster is similar to that of other young star clusters in
the Milky Way. It has now been recognized that the three brightest
stars in the centre, which had appeared to be more massive than
theoretical limits allow, may actually consist of two or more
individual massive stars whose light has blended together. Even with
the resolution of Hubble it is not possible to separate the individual
stars in each of the three systems. That finding agrees with a
previous study which measured the largest individual mass at roughly
115 solar masses, which is within the acceptable limits.


CLOSE COMET ENCOUNTER PRODUCES SURPRISES
Science Daily

In February the spacecraft Ulysses, which is on a mission to study the
Sun's polar region, flew through the tail of Comet McNaught.
University of Michigan scientists said that the spacecraft not only
detected unexpected ions, but also indicated that, even at 160 million
miles from the comet's nucleus, the tail slowed the solar wind from
its normal speed of about 700 km/s to less than 400 km/s.


EARLY DATE FOR OXYGEN ON EARTH
NASA

Researchers report that traces of oxygen appeared in Earth's
atmosphere from 50 to 100 million years before what is known as the
Great Oxidation Event, which is supposed to have happened between 2.3
and 2.4 billion years ago, a time when some scientists think that
atmospheric oxygen increased significantly from previous very low
levels. Scientists analysed the amounts of the trace metals
molybdenum, rhenium and uranium in a kilometre-long drill core from
Western Australia, representing the time just before the major rise of
atmospheric oxygen. The quantity of these metals in oceans and
sediments is said to depend upon the amount of oxygen in the
environment.

One possible explanation for the Great Oxidation Event is that the
ancient ancestors of today's plants first began to produce oxygen by
photosynthesis. However, some scientists think that organisms began
to produce oxygen much earlier, but the oxygen was destroyed in
reactions with volcanic gases and rocks. The new evidence shows some
oxygen in the environment 50 to 100 million years before its big
increase, which strengthens the notion that organisms learned to
produce oxygen long before the Great Oxidation Event, and that the
rise of oxygen in the atmosphere was ultimately controlled by
geological processes.


SOLAR ANALOGUE
New Scientist

Astronomers have found the most Sun-like star yet. The star, called
HD 101364, is a little more than 200 light-years away. Its size,
mass, temperature, and chemical make-up are all so similar to the
Sun's that no measurable differences could be found in high-resolution
observations made by the 2.7-metre telescope at the McDonald
Observatory in Texas. Other very Sun-like stars have previously been
identified, including 18 Scorpii, HD 98618, and HD 195034. But those
three stars have several times more lithium than the Sun, while
HD 101364 is almost identical to the Sun in that respect as well,
making it an even closer match. The star does differ in one way from
the Sun -- it appears to be about 1 billion years older. Astronomers
at McDonald Observatory have been looking for evidence of planets
around HD 101364, but they have not found any.


FUSE REACHES THE END
Johns Hopkins University

The space telescope known as FUSE has finally reached its mission's
end and will be turned off after more than eight years of discoveries
on everything from planets and nearby stars to galaxies and quasars
billions of light-years away. FUSE, short for Far Ultraviolet
Spectroscopic Explorer, had its original three-year mission extended
by NASA three times. Scientific highlights from FUSE include a
glimpse into molecular hydrogen in Mars' atmosphere, confirmation of a
halo of hot gas surrounding the Milky Way, and the first observation
of molecular nitrogen outside the Solar System.


LONG-LOST ASTEROID IS FOUND AGAIN
Science Daily

It seems that, in accordance with the modern passion for categorizing
everything and assigning grandiose names, all asteroids that are
thought to be more than 150 m in diameter and that come to within 0.05
astronomical units of the Earth's orbit are designated Potentially
Hazardous Asteroids. The implication that they are liable to hit the
Earth at any foreseeable time is of course not a valid one. According
to the present count there are 886 of them; one of them, supposedly
recently discovered and assigned the temporary identification 2007
RR9, has proved to be identical with a long-lost object called 6344
P-L which was first observed nearly half a century ago and last seen
in 1960. It has been suggested that the object, which is in a
4.7-year orbit that takes it nearly out to Jupiter's orbit, may in
fact be not so much an asteroid as a now-dormant comet nucleus; so
far, however, no activity has been seen, but the object is still
approaching closer to the Sun. It will pass closest to the Earth at
0.07 AU on November 6, but will still appear only about magnitude 19.


MASSIVE STELLAR BLACK HOLE
Chandra X-ray Observatory

Astronomers think that they have located an exceptionally massive
stellar black hole in a 3.5-day binary system in M33, a galaxy about 3
million light-years away. By combining data from the Chandra X-ray
observatory and the Gemini telescope in Hawaii, the mass of the black
hole, known as M33 X-7, was found to be 15.7 times that of the Sun -
the highest value known. A stellar black hole is supposed to be
formed from the collapse of the core of a massive star at the end of
its life. The observation raises (but does not answer) all sorts of
questions about how such a massive black hole could have been formed.


SHARPEST VIEW OF PLUTO
University of Hawaii

It is almost 30 years since the discovery of Pluto's principal
satellite, Charon. Recently, on September 5, an improved adaptive-
optics system was used on one of the twin Keck telescopes in Hawaii to
take an image of the Pluto system with a resolution at least
comparable with that obtainable with the Hubble telescope. Favourable
factors included good natural seeing, improved sensors in the
adaptive-optics system, and Pluto being at its maximum brightness.
The new images, which have a resolution of about 35 milliseconds of
arc, are about 20 times sharper than those taken 30 years ago. The
new image, stacked from 16 individual images taken in the course of an
hour, clearly shows Nix and Hydra, Pluto's small satellites discovered
with Hubble in 2005. The new satellites are thought to be less than
100 km in diameter and are both about visual magnitude 23.5; Charon is
about 1200 km across and Pluto, which is about 14th magnitude, 2300
km.


ROVERS GET ANOTHER EXTENSION
NASA

NASA is extending, for a fifth time, the activities of the Mars
exploration rovers Spirit and Opportunity. That is to say, it will
continue to pay the salaries of the people who plan the activities of
the rovers and look at (and try to understand) the pictures that they
return, and will also continue to fund the operation of the radio
antennae involved in the reception of the data. The decision keeps
the robotic explorers active on opposite sides of Mars, possibly until
2009. The extended mission is dependent upon the continued
operability and productivity of the rovers. The twin rovers landed on
Mars in 2004 January on missions originally planned to last 90 days.
In September, Opportunity began descending into Victoria Crater in
Mars' Meridiani Planum region. About half a mile wide and 230 feet
deep, it is the largest crater that the rover has visited. Spirit
climbed onto a volcanic plateau in a range of hills that were on the
distant horizon from the landing site.

After more than three-and-a-half years, Spirit and Opportunity are
showing signs of age, but they are in good health. Each carries
instruments to examine the 'geology' of Mars for information about
past environmental conditions. Opportunity has returned evidence that
its area of Mars was wet for an extended period of time long ago, with
conditions that could have been suitable for sustaining microbial life
if any had existed there; Spirit has found that water in some form has
probably altered the mineral composition of some soils and rocks in
the region it is exploring. To date, Spirit has driven 4.51 miles at
an average speed of 0.00015 mph and has returned 102,000 images, an
average of about one every 18 minutes or every three inches of travel;
Opportunity has driven 7.19 miles and has returned 94,000 images.


GALAXY CLUSTER MODELS CAST DOUBT ON DARK MATTER
RAS

For almost 75 years, there have been astronomers who have believed
that the Universe has a large amount of unseen or 'dark' matter,
sometimes thought to make up about five-sixths of the matter in the
cosmos. With the conventional theory of gravitation, based on
Newton's ideas and refined by Einstein, dark matter helps to explain
the motion of galaxies, and clusters of galaxies, on the largest
scales. Now two Canadian researchers at the Perimeter Institute for
Theoretical Physics suggest that the motion of galaxies in a distant
cluster is more easily explained by a Modified Gravity theory than
by the presence of dark matter.

The two scientists analysed images, made with the Hubble telescope,
the Chandra X-ray and Spitzer infrared observatories, and the Magellan
telescope in Chile, of the 'Bullet Cluster' of galaxies. The cluster
consists of two merging clusters of galaxies and lies at a distance of
over 3 billion light-years in the southern constellation Carina. The
observations mapped the very hot gas between the galaxies and showed
the effect of the cluster in acting as a gravitational lens,
deflecting the path of light emitted by a background galaxy. Previous
studies have been held to suggest that the Bullet Cluster clearly
demonstrates the presence of dark matter, but the researchers do not
agree: they consider that the observed gravitational lensing and
distribution of gas is more naturally explained by a revised theory of
gravitation. The two physicists are enthusiastic about their
findings; they will need to maintain their enthusiasm over the long
term as well as to provide more, and at least equally cogent,
demonstrations of their ideas if they are to carry the astronomical
world with them.


CHINA LAUNCHES MOON ORBITER
BBC Online

China has launched its first lunar orbiter, on a mission planned to
last a year. The satellite, named Chang'e 1, was launched from the
Xichang Centre in south-west China's Sichuan province on October 24.
Analysts say that it is a key step towards China's aim of putting a
man on the Moon by 2020, in the latest stage of an Asian space race
with Japan and India. Earlier this month, a Japanese probe entered
orbit around the Moon, and India is planning a lunar mission for April
next year. The Chinese satellite is expected to enter lunar orbit in
early November and start sending back pictures of the Moon's surface
later that month.




Bulletin compiled by Clive Down

(c) 2007 the Society for Popular Astronomy


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