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 Post subject: ENB No 247 July 6 2008
PostPosted: Sat Jul 05, 2008 6:34 pm 

Joined: Fri May 16, 2008 10:09 pm
Posts: 222
Location: Headcorn, Kent, England
Electronic News Bulletin No. 247 2008 July 6

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

Two fresh near-UK fireballs have been notified to the Section since last
time, both from the last week of June:

Date Time (UT) Magnitude and Notes Observed from
08/06/23-24 ~22:38 At least -6/-9; 2 reports Guernsey & Hants
08/06/28-29 ~22:27 -4/-8?; 2 reports Worcs & W London

Initial sighting notes on the June 23-24 fireball (though it is not certain
both reports were of the same object) can be found at: on the UK Weather World's Space Weather
Forum, while one sighting of the June 28-29 fireball, with a shaky, hand-
held image of the trail's fragmentation, is at: on
the SPA's Observing Forum. This meteor may have been heading
roughly south to north over eastern England or perhaps partly over the
nearby North Sea, from a preliminary examination of the data.

More observations of these or other fireballs seen from Britain and
places close-by (a fireball is any meteor that reaches at least magnitude
-3) are always welcomed by the Section. Details to send are outlined
on the "Fireball Observing" page of the SPA website, at: .

BBC Online

A plausible explanation has been put forward as to why the northern
and southern hemispheres of Mars look so different. Mars' crust is
thicker in the southern hemisphere, and magnetic anomalies are found
in the south but not the north. New studies suggest that an asteroid
about the size of the Moon (much bigger than any that exist now) may
have collided with the northern part of Mars in early in the history
of the Solar System, at much the same time as an even bigger impact on
the Earth has been hypothesized to have created the debris that
condensed to become the Moon.

The whole of Mars' northern hemisphere is a lowland basin which might
once have held a great ocean. The southern hemisphere, on the other
hand, comprises rugged, crater-pitted highlands with altitudes up to
8000 metres higher than the north. The new research, which is based
on data from two orbiting spacecraft, Reconnaissance Orbiter and
Global Surveyor, suggests that Mars bears the largest impact scar
known in the Solar System. There is, however, an alternative theory
which proposes that the dichotomy of character between the two
hemispheres of Mars is the result of enormous volcanic disruption 3.8
billion years ago.

University of Cambridge

A fresh look at surface images suggests that a clash of lava and ice
may have been responsible for a major flood on Mars not long ago.
Mars' ice caps are scarred by huge chasms. Astronomers from the
University of Cambridge reckon that they have found volcanic ridges
and craters in exposed rock at the base of one chasm in the north
polar ice cap. Scours that suggest huge flows of water represent
circumstantial evidence linking the volcanic features to the outburst
flood thought to have formed the chasm. The volcanic features are
thought to be between 20,000 and 10 million years old, so there is an
indication that liquid water may have been present on Mars' surface
relatively recently.

NASA/Jet Propulsion Laboratory

The Phoenix Mars Lander included four 'wet-chemistry cells' to enable
it to perform chemical analyses of the soil within reach of its
digging arm. It has just used the first one, and has returned a
wealth of data for analysis. One inch into the surface layer, the
soil is very alkaline, and contains salts that include magnesium,
sodium, potassium and chloride ions and others not yet identified.
Mineralogically the sample is very much like terrestrial soil, and
appears to be closely analogous to surface soils found in the upper
Dry Valleys in Antarctica.

Another analytical Phoenix instrument has baked its first soil sample
to 1,000 degrees Celsius to find out which gases are released at a
range of temperatures to identify the chemical make-up of soil and
ice. Lander cameras confirmed that white chunks exposed during
trench-digging were water-ice because they sublimated, or vaporised,
over a few days.


It has been suspected that the extra-bright cores of certain spiral
galaxies known as Seyfert galaxies are powered by super-massive black
holes consuming a lot of material. However, it has not been clear
where the material has come from of how it started on its journey
toward the black hole. One theory was that Seyfert galaxies have been
disturbed by close encounters with neighbouring galaxies, thus
stirring up their gas and bringing more of it within the gravitational
reach of the black hole, but in optical images only a small fraction of
Seyfert galaxies showed any evidence of such encounters. Recent
images, however, obtained with the Very Large Array radio telescope,
of hydrogen gas in Seyferts show that the majority of them are, in
fact, disturbed by ongoing encounters with neighbouring galaxies.

Max Planck Institute

The laws of nature are the same in the distant Universe as they are
here, just as we have always supposed. The Effelsberg 100m radio
telescope has made spectroscopic observations of a distant quasar
called B0218+367, whose light is partially absorbed by ammonia gas in
an intervening galaxy. The wavelengths at which ammonia absorbs radio
energy are sensitive to the proton-electron mass ratio, and the
observations show that that ratio is the same, 1836, in the galaxy
6 billion light-years away as it is on the Earth.

Jet Propulsion Laboratory

Cassini has completed its four-year initially-intended mission but is
going to be operated for (at least) another two years. Among other
things, Cassini has revealed many details of Saturn's moons Titan and
Enceladus. Those two satellites are the primary interest for the
2-year extension, which will also allow for monitoring seasonal
effects on Saturn and Titan, exploring new parts of Saturn's
magnetosphere, and observing the ring geometry at the Saturn equinox
in 2009 August, when sunlight will shine on the rings edge-on.


The SOHO (SOlar and Heliospheric Observatory) spacecraft has just
discovered its 1500th comet, making it more successful than all other
comet discoverers throughout history put together. The location of
SOHO between the Sun and the Earth gives it a big advantage over
everybody else; from the surface of the Earth we can see regions close
to the Sun clearly only during an eclipse.

Roughly 85% of SOHO discoveries are fragments from a once-great comet
that split apart in a very close pass around the Sun many centuries
ago. The fragments are known as the Kreutz group and pass within a
million km of the Sun's surface when they return from deep space.
At such proximity, most of the fragments are finally destroyed,
evaporated by the Sun's radiation -- SOHO sees them arriving but they
do not leave. The images are obtained by the Large Angle and
Spectrometric Coronograph (LASCO), one of 12 instruments on board.
LASCO itself does not make the detections; that task falls to an open
group of highly-skilled volunteers who scan the data as soon as they
are downloaded to Earth. Once SOHO transmits the data, they can be on
the Internet and ready for analysis within 15 minutes. Enthusiasts
from all over the world look at each individual image for a tiny
moving speck that could be a comet. People who believe that they have
found one submit their results to the Naval Research Laboratory in
Washington DC which checks all the SOHO findings before submitting
them to the Minor Planet Center, where the comet is catalogued and its
orbit calculated.

The SPA Electronic News Bulletins are sponsored by the Open University.

Bulletin compiled by Clive Down

(c) 2008 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
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