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 Post subject: ENB No. 201 July 23 2006
PostPosted: Sun Jul 23, 2006 11:23 am 
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Electronic News Bulletin No. 201 2006 July 23

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

By Guy Fennimore

The next SPA meeting will take place on July 29. Please note that we
are at a new venue, and the meeting will start at a new time of 2.00
The venue is the Khalili Lecture Theatre at the School of Oriental and
African Studies (SOAS), Thornhaugh Street (off Russell Square),
London WC1. Readers of "Popular Astronomy" can find a map on
page 42 of the July-September issue. On arrival at SOAS look for the
SPA table to obtain your visitor's badge that has to be worn whilst in
building, or enquire at main reception.

By Alastair McBeath, SPA Meteor Section Director

Slightly belatedly for the 200th ENB, but some celebratory meteoric
fireworks finally arrived in the middle of July, with at least three
UK fireball events (meteors of at least magnitude -3) reported so far.

The first was around 00:15 UT on July 13-14, estimated as of about full
Moon brilliance (magnitude -13 or so), spotted by a single witness in

In strong twilight not long after sunset on the next night, July 14-15,
observers or groups of observers saw a very bright fireball around
20:47 +/- 2 mins UT, the lucky people in Worcestershire, Lincolnshire,
Surrey and Somerset. The bright sky made estimating the object's
magnitude difficult, but a conservative range would probably be about
-6 to -10, possibly brighter. Details are still to be confirmed, but the
initial sightings have suggested a possible east to west trending
trajectory, perhaps partly over Oxfordshire-Gloucestershire.

The third event happened at about 23:52 +/- 2 mins UT on July 18-19,
seen from Essex and Hertfordshire. It was probably in the -5 to -9
magnitude range, and seems to have been heading generally south to
north either over the extreme east of Essex and Suffolk-Norfolk, or the
North Sea offshore of there, judging by the details to date.

In all cases, fresh sightings would be extremely welcome to help refine
the estimated parameters given here, along with any other fireball
reports. More information on what information to send and where to
can be found via the Section's "Fireball Observing" page at: .

The Register

Next month, NASA is to launch a new solar observatory to observe the
Sun in three dimensions for the first time, possibly leading to better
forecasting of 'space weather' and a clearer understanding of certain
processes at work in the Sun. The Stereo mission (Solar-TErrestrial
RElationships Observatory) consists of two near-identical spacecraft,
which will record data in the ultraviolet and will use a coronagraph
to study the outer atmosphere of the Sun. They will both be launched
into solar orbits, but in different directions so that they will
gradually drift further and further apart, sending back data on solar
activity from two angles at once.

Currently, even with the SOHO observatory, we can really see the
Sun only from the Earth's point of view, so we get a rather one-
dimensional picture. We see material being ejected from the solar
limb, but it is impossible to tell whether it is heading towards the
Earth unless and until it hits SOHO itself, giving us just an hour's
notice. Stereo will make observations of the Sun from side-on, so
enabling us to track material from coronal mass ejections (CMEs)in
three dimensions. The progress of the CMEs will be monitored by a
device called a heliospheric imager, built at Birmingham University.
We should get warning of up to two and a half days when CMEs are
coming towards the Earth -- good news for satellite owners, power
companies and mobile-phone operators, all of whose businesses can be
disrupted by big CMEs.


Harry Potter author J.K. Rowling now has an asteroid named in her
honour. The honour was bestowed by the International Astronomical
Union, who named asteroid no. 43844 'Rowling.' Dr. Mark Hammergren,
who discovered the asteroid, is an astronomer at the Adler Planetarium
in Chicago and submitted the name 'Rowling' to the committee for
consideration. The citation reads:

(43844) Rowling = 1993 OX2
The British author Joanne 'Jo' Rowling (b. 1965) is best known for
her beloved fantasy series featuring the young wizard Harry Potter.
Her books have won numerous awards, inspired a love of reading in
children around the world and entertained millions of all ages.


The IAU has announced that the satellite S/2005 S 1 has been given the
designation (and name) Saturn XXXV (Daphnis).

New Scientist

The smaller of Jupiter's red spots, Oval BA, which initially formed
when two white ovals merged in 1998 and were joined by a third in
2000, made its closest approach to the Great Red Spot on about July
15, when the edges of the storms were about 3500 kilometres apart.
They will probably have passed one another completely by the end of
July. The close approach has not visibly diminished the strength of
the smaller storm. Oval BA turned from white to red earlier in 2006,
and astronomers think it is likely that the colour is tied to storm
strength, because when the internal wind speeds of Oval BA
strengthened to match those of the Great Red Spot the hue of Oval BA
also changed to match that of the larger storm. Although the two
storms are passing relatively close to one another, there is no chance
of their merging, because jet streams keep each corralled into its
own zone of latitude.

Universe Today

The Alpha Centauri system was first recognized as the closest star
system in 1839 by the Scottish astronomer Thomas Henderson. Using the
parallax method, he calculated that Alpha Centauri was 2.7 light-years
away; the modern value is 4.4 light-years. Proxima Centauri took the
title of closest star when its parallax was measured accurately in
1917, and it was found to be only 4.2 light years away. Since Proxima
is so close to the double star Alpha Centauri, and moving in the same
direction across the sky, astronomers have always assumed that they
constitute a triple-star system. A group of researchers cast doubt
upon that assumption about 12 years ago, claiming that the
differential velocity of Proxima with respect to the centre of gravity
of the Alpha Cen pair was too great for gravity to hold the system
together. But Hipparcos and other new measurements now once again
allow the possibility that Proxima IS a gravitationally bound member
of the system.

The Register

It seems that China's ambitious space-exploration plans -- already
encompassing the Moon -- also extend to Mars. China intends to launch
its first lunar probe next year. The year-long mission to gather
'three-dimensional images and data on the Moon's surface and
environment' is the first part of a three-stage project which also
promises a lunar vehicle by 2012 and a rock-collecting module by 2017.
However, the deputy head of China's space programme declared in June
that they would get a man on the lunar surface by 2024, suggesting a
four-stage Moon plan. It has now been announced that in the next five
years "China will, on the basis of its Moon probes, actively plan
deep-space exploration, focusing on lunar and Mars exploration".

New Scientist

Observations of a recent outburst (explosion) in the recurrent-nova
system RS Ophiuchi have led to a suggestion that such systems may be
the origin of Type Ia supernovae, which are important to astronomers
because they are used as 'standard candles' to estimate distances.
Novae, recurrent novae and cataclysmic binaries are all binary-star
systems consisting of a red giant star in orbit with a white dwarf.
The outbursts occur because the white dwarf slowly collects gas shed
by the red giant. When enough gas has accumulated on the surface of
the white dwarf, the mounting pressure triggers a nuclear explosion.
Such an explosion occurs in RS Ophiuchi every few decades, but not
with clockwork regularity; the previous outburst was in 1985. The
recent one occurred on 2006 February 12 and has been observed in more
detail than previous ones. A possible connection with Type Ia
supernovae is that such objects have been thought to originate in
binary systems of the same sort as RS Oph, but in which the white
dwarf reaches a critical mass at which the ensuing explosion does not
simply burn the newly collected material but involves and disrupts the
whole star. Observations of the X-rays emitted during the recent
outburst of RS Oph allowed the observers to estimate the mass of the
white dwarf that produced it. It seems to be close to the critical
mass that would trigger a supernova.

(c) 2006 the Society for Popular Astronomy

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