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 Post subject: ENB No. 198 June 11 2006
PostPosted: Sun Jun 11, 2006 3:22 pm 
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Electronic News Bulletin No. 198 2006 June 11

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

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 the bulletin.

By Alastair McBeath, SPA Meteor Section Director

As discussed in ENB 197, observers were being encouraged to check
for any potential activity due to dust trails laid down by Comet
73P/Schwassmann-Wachmann 3 (SW3), between May 28 to June 6 this
year, the interval the Earth was expected to pass closest to material
by the comet since 1801. The miss distance was quite considerable
however, and the chances for any meteors were expected to be low. Early
details reaching the SPA suggests that virtually no possible SW3 meteors
were seen during this most likely interval, with a run of good weather
falling nicely for parts of the UK during some of this time, to allow
observers at least a casual view. Some initial comments can be found on
the SPA's Observing Forum "Possible SW3 meteors" topic at: .

Information from the International Meteor Organization's Visual
Commission Director, Rainer Arlt, indicated observed activity he had
received from across the world was typically zero SW3 meteors an hour,
with a very few people occasionally reporting one "possible" or so.
that a proportion of sporadic meteors may seem to line up with any
radiant area simply by-chance, observed visual activity this low cannot
regarded as genuine without some form of instrumental confirmation (such
as photos or videos), unless most visual observers reporting
saw similar meteor numbers at the same time. This was not the case here,
so it seems no genuine SW3 meteor rates occurred, as far as the
preliminary results allow us to tell.

Though not too interesting for the observers involved, such negative
reports are very important, since in this case, they help give
confidence in
the theoretical dust stream model used, because they appear to confirm
the model's predictions. While the comet has broken apart so
spectacularly now, future years may still bring the potential for
from it, such as in 2011, and observers need to be aware that as the
night twilight kicks in for Britain in each late May, things may not
necessarily be so quiescent astronomically as might be supposed.

Meanwhile, and again as discussed in the previous ENB, there are other
possible showers to look out for in the twilight of the next few weeks,
aside from more noctilucent clouds, whose season started well and
unusually early from recent years in late May - see the SPA Forum Topic
"Noctilucent clouds" for some early details and web-addresses to check,
at: .
Meteorically, there may be some June Lyrids around June 16, and the
June Bootids towards the end of the month. Notes on these and other
meteor showers active in June can be found off the meteor homepage at: .

By Alastair McBeath, SPA Meteor Section Director

Around 00:05 UT on June 6-7, a brilliant fireball was observed crossing
the still daylight "night" sky of north Norway, travelling roughly WSW
ENE. At 00:13 UT, seismic recorders at Karasjok in southern Finnmark
detected a meteoritic impact event, and witnesses reported hearing sonic
booms minutes after the fireball flew over, plus ground tremors. One
observer, farmer Peter Bruvold in Lyngseidet, central Troms, was out
tending his stock, with a camera on-hand because he was expecting one
of his mares to produce a foal. He saw and heard the meteor, and had the
presence of mind to photograph it in mid-flight. Although information is
still sketchy, early details suggested a possible fall zone somewhere in
~100 km diameter area centred on the Reisadalen area of eastern Troms,
perhaps near 21.3 deg E, 69.5 deg N. Preliminary comments suggested
this may have been the largest meteorite to strike Norway in historical
times, perhaps significantly more massive than the Alta meteorite of
which weighed about 90 kg. More details can be found at: which
includes a map of the fall area and the meteor photo.


Some scientists at Ohio State University have suggested that an
asteroid crashing into what is now Antarctica may have caused the
biggest mass extinction in the Earth's history and have spawned the
Australian continent. They say that a crater 300 miles in
diameter is now hidden more than a mile beneath the East Antarctic
ice sheet, in the Wilkes Land region, south of Australia. Gravity
measurements that reveal its existence suggest that it could date back
about 250 million years -- the time of the Permian-Triassic
extinction, when a large proportion of animal life on the Earth died
out. Scientists believe that the Permian-Triassic extinction paved
the way for the dinosaurs to rise to prominence. The Wilkes Land
crater is more than twice the size of the Chicxulub crater in Mexico's
Yucatan peninsula, which marks the impact that may have ultimately
killed the dinosaurs 65 million years ago, so the impacting asteroid
could be supposed to have been correspondingly bigger as well. The
location of the crater also suggests that it might have triggered a
delayed break-up of the Gondwana super-continent. Some 100 million
years ago, Australia split from the ancient Gondwana and began
drifting north, pushed away by expansion of a rift valley into the
eastern Indian Ocean. The rift cuts directly through the crater, so
it might seem that the impact helped the rift to form.


Two storms circling Jupiter are about to converge. Jupiter has no
visible solid surface, and different features seen in its clouds give
slightly different apparent rotation periods for the planet, so they
exhibit progressive changes in relative longitude. Objects in
adjacent latitudes can even appear to overtake one another. Such an
event is likely to take place about the beginning of July between the
Great Red Spot, which is twice the size of the Earth, has winds
blowing at 350 mph, and has been in existence for hundreds of years,
and 'Oval BA', which is half its size and only six years old. Similar
encounters have happened before, in 2002 and 2004, and both storms
survived apparently unaltered.


Hot, massive stars (and many others) tend to expel material from their
surfaces as outflowing winds. The ejected material can interact with
other nearby stars, contribute matter and energy to the interstellar
medium, and even induce new star-formation. Hot massive stars thus
play a significant role in gAlactic evolution. One such star is Tau
Scorpii, which is luminous enough to be easily visible with the unaided
eye despite its distance of over 400 light-years. With a mass as much
as 15 Suns, Tau Scorpii is much bigger and hotter than our own star.
Such massive stars are relatively rare, and Tau Scorpii is actually
one of our closest massive neighbours.

Massive stars are thought to emit X-rays because of supersonic shocks
occurring within their outflowing winds. However, Tau Scorpii is an
unusually strong X-ray source compared to stars which have seemed
otherwise similar. Its enhanced emission is now attributed to its
newly discovered magnetic field. According to the discovery team, the
field is most probably a relic from the star's formation, and it
interacts with the wind, forcing it to flow along magnetic field
lines, like beads along wires. Wind that blows along 'open' field
lines can freely escape the star, something that winds in looped
fields cannot achieve. The result is that, within each magnetic loop,
wind-flows from both footprints on the surface of the star collide
with one another at the loop summits, producing tremendously energetic
shocks that heat the wind material to million-degree, X-ray-emitting
plasma that is tied to the magnetic loops. The model thereby explains
why Tau Scorpii is such an intense X-ray emitter. However, it is not
clear whether it could have been the magnetic field that somehow
slowed down the rotation rate of the star to less than one-tenth that
of otherwise similar, non-magnetic, massive stars.


Two new ESO studies show that objects only a few times more massive
than Jupiter may be born with discs of dust and gas, so analogues of
Jupiter's satellite system might circle objects that are some 100
times less massive than our Sun. The same appears to be true for
their even punier cousins, sometimes called planetary-mass objects.
Such objects are supposed to have masses similar to those of
extra-solar planets, but they are not in orbit around stars --
instead, they exist independently in space. Optical spectra of six
candidates identified recently by researchers at the University of
Texas suggest that two of the six have masses between five and 10
times that of Jupiter while two others have 10 to 15 times Jupiter's
mass. All four objects are just a few million years old and are
located in star-forming regions about 450 light-years from Earth.
They show infrared emission from dusty discs that could possibly
evolve into miniature planetary systems.


The space ship that will go to the Moon should be ready for tests in
2012 and for manned flight in 2014. NASA plans to retire its ageing
shuttle fleet, which has suffered two tragic disasters, by 2010, and
replace it with a vehicle to take astronauts back to the Moon by 2020.
The current shuttle fleet has not gone to the Moon. Astronauts first
landed on the Moon in 1969 but none has been there since 1972.


Astronomers using the Far Ultraviolet Spectroscopic Explorer (FUSE)
satellite launched in 1999 have discovered large quantities of carbon
mixed with a cloud of dust surrounding the young star Beta Pictoris.
The abundance of carbon in the dust disc surrounding the star means
that the planets that may be being formed could be rich in graphite
and methane, much like those of our Solar System are supposed to have
been in their early stages. The star is 1.8 times the Sun's mass and
lies 60 light-years from Earth. Its disc was discovered in 1984, and
images taken by the Space Telescope suggest that it may have a
Jupiter-type planet already.


Philip's The Sky at Night Volume 2 is the latest volume in Sir
Patrick Moore's series of essays written to accompany the 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
Published last year:
Philip's Solar System Guide by Peter Grego describes how to observe
not only the planets but also the Moon, Sun, comets, meteors,
asteroids and other objects in our Solar System -- £9.99
Philip's Solar System Observer -- a pack for the amateur Solar-System
observer. It contains three items: Philip's Solar Observer's Guide,
Philip's Map of the Solar System and Philip's Solar System Phenomena
poster -- £12.99

Bulletin compiled by Clive Down

(c) 2006 the Society for Popular Astronomy

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