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The SOCIETY for POPULAR ASTRONOMY
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Electronic News Bulletin No. 212 2007 January 7
====================================================


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 http://popastro.c.topica.com/maafwHpabvLVfcixLLVb/


SPECIAL MEMBERSHIP OFFER

If you are not already a member of the SPA now is a great time to
join! We are offering to those who receive ENBs and are not already
members a special joining price of only £12.00, saving £3.00 on the
usual UK annual rate. (Overseas rates vary, but discount still
applies -- see our website for details.) You will also receive, free,
three CD-Roms -- 'Window on the Universe' Parts 1 and 2, and 'Window
on the UK'

Join NOW by going to our secure website at www.popastro.com and click
the 'join now' button. To claim the your discount enter ENB017 when
asked for your voucher reference. To join by post send your details
with payment (£12.00 -- 1 year or £24.00 -- 2 years -- UK rate) to
SPA Membership, 36 Fairway, Keyworth, Nottingham, NG12 5DU, quoting
reference ENB017.

Please Note -- This offer is valid only until 2007 February 28 and
does not apply to renewals of membership.


MORE URSID NEWS
By Alastair McBeath, SPA Meteor Section Director

Thanks to a most helpful rapid response from various observers, analysts
and commentators, I have managed a more detailed review of what
the Ursids may have done across their expected peak time on
December 22-23, to what was published last time. Most of the data is
available on the Meteorobs (http://www.meteorobs.org) archive, with
an earlier summary posted on IMO-News on January 2
(http://www.imo.net). Most of the Meteorobs reports were kindly
collected and forwarded to the Section by Rich Taibi. It seems clear
an Ursid outburst definitely did happen on December 22, but the
timing and strength are still somewhat uncertain, so these notes remain
preliminary only and are liable to be amended as more results arrive.

Early radio results suggest enhanced activity probably due to the Ursids
was present from around 13h-14h to at least 20h-21h UT on that date,
including details from Mike Boschat's report on Meteorobs (Nova
Scotia, Canada), and David Entwistle's data and discussions (England).
Chris Steyaert's initial analysis of the three results' sets that best
showed
this (using a new radio reduction method outlined in the June 2006
International Meteor Organization - IMO - journal WGN, 34:3), those
of Enric Fraile Algeciras (Spain), Jeff Brower (British Columbia,
Canada) and Dave Swan (England), gave Ursid-related maxima at
16:30 UT for Swan and 18:30 UT for Algeciras. Jeff Brower estimated
a possible peak time from his own results of around 20:00 UT.

Visual results have proven far fewer than we might have hoped so far,
but there are hints that enhanced activity at or above the usual peak
level, that is Zenithal Hourly Rates - ZHRs - ~10+, may have been
present as early as 10:30-13:00 UT on December 22, over western
North America (results on Meteorobs from Bruce McCurdy in
Alberta, Canada, and Wesley Stone in Oregon, USA). A two-hour
watch reported similarly by Bill Godley in Oklahoma, USA, from
06:30-08:00 UT on December 22 produced just one Ursid however,
inferring the start of the enhancement as after 08h UT, but probably
before 13h.

The IMO-predicted ~19h-21h UT peak interval (expanded to perhaps
begin around 18h by the predictions of Esko Lyytinen and Markku
Nissinen outlined in the December 19 Special ENB) was partly
covered by four watchers in Europe - Jure Atanackov in Slovenia,
Michel Vandeputte in Belgium, Thomas Weiland in Austria, and myself
in England. Combining these results suggests averaged ZHRs of order
30 +/- 10 from roughly 18h-20h UT. The hour centred at ~18:40 UT
may have produced the marginally stronger level, but the difference
seems relatively small compared to the following hour. This was partly
confirmed by a preliminary analysis of just Michel's and my data by
Carl Johannink. Activity seemed to have dropped back somewhat after
20h UT, to ~25 +/- 10 in the hour centred about 20:45, and had
apparently descended to the usual peak level, so ZHRs again ~10, by
~23h UT, though only Thomas Weiland had conditions good enough
to allow watching much beyond ~21h then.

Video observations from Sirko Molau in Germany, posted on
IMO-News on December 28, suggested healthy Ursid rates were
present from when the sky was dark enough for his automated system
to begin recording at 17:00 UT till about 02:00 UT. His initial analysis
hinted at a possible peak around 21:30-22:00 UT, significantly later
than what the visual and radio results seemed to indicate.

Data from December 23 (Audrius Dubietis, Lithuania, and Paul
Martsching, Iowa, USA - Paul's via Meteorobs) and 24 (George
Gliba, West Virginia, USA, also on Meteorobs) showed Ursid activity
at barely detectable levels, with observed rates of just one or two per
hour.

The overall impression is one of a stronger than normal Ursid maximum
on December 22, peaking perhaps in the hour centred at 18:30-18:40
UT, or more probably in the 19h +/- 1 hour UT interval, with mean
ZHRs of ~30, set against a background of rates at least equal to the
typical "normal" peak, which were present from maybe 12h to 23h UT,
as far as the available results allow. This seems to support the idea
that
the possible broad Ursid filament, predicted by NASA SETI Institute
member Peter Jenniskens to have rates above half the maximum level
from ~09h-02h UT on December 22-23, may have been partly
encountered, albeit no maximum as he suggested for ~17:38 UT was
apparent in these results, and it seems unlikely the stronger-rates
interval
was so long-lived as this either. In respect of the Lyytinen-Nissinen
prediction of a chiefly faint-meteor peak around 19:27 UT, set in a
trail
filament persisting from ~18:10-20:50 on December 22, well-enhanced
Ursid rates were distinctly present from at least ~18h-21h UT, but there
was no good evidence in either the visual, early radio or video results
for a peak (whether of visually-faint meteors or not) especially close
to that expected time.

Very many thanks go to all the named contributors above for their
willingness to share their results and/or preliminary analyses so soon
after the event. All further Ursid results would be very welcome. For
visual watchers, the Section's homepage at:
http://popastro.c.topica.com/maafwHpabvLVgcixLLVb/ has details of what
to
send and where to.


HIGH SOLAR ACTIVITY IN PROSPECT
NASA

On the basis of historical records of geomagnetic storms, there have
been some suggestions that solar cycle 24, due to peak in 2010 or
2011, will be a particularly active cycle. Scientists have looked at
records of geomagnetic activity stretching back almost 150 years and
noticed that the amount of geomagnetic activity at a given time
correlates with solar activity 6 to 8 years later. If such a
correlation has predictive power in the present instance, the next
Solar Maximum should peak around 2010 with a sunspot number of 160
plus or minus 25. That would make it one of the most active solar
cycles of the past fifty years, or indeed of recorded history.
Astronomers have been counting sunspots since the days of Galileo,
watching solar activity rise and fall every 11 years. Curiously, four
of the five most active cycles on record have come in the past 50
years.


NEW TYPE OF MASSIVE-STAR DEATH?
Science Daily

A team of astrophysicists from the University of Copenhagen monitored
two long-duration Gamma-ray bursts (GRBs) last summer. They concluded
that there were no supernovae associated with those two Gamma-ray
bursts. There are two possible conclusions: 1) that those GRBs were
not caused by massive stars, or 2) that they were caused by massive
stars that did not cause associated supernova explosions.

In the better-observed case the burst occurred in a small spiral
galaxy, in a compact star-forming region in one of the spiral arms.
That indicates that the star that caused that GRB may well have been
massive, as it is taken as axiomatic that GRBs are associated with
some late stage in a star's evolution, and the only stars that could
have reached such a stage in a star-forming region are massive ones
which have lifetimes of only a few million years. So whereas it has
been thought that massive stars die in supernova explosions, it now
seems that may not always be the case.


WHITE DWARF HAS METAL-RICH RING OF GAS
Astronomy

Astronomers have discovered a ring of metal-rich gas surrounding a
relatively nearby white-dwarf star, called SDSS1228+1040, about 460
light-years away in the constellation Virgo. University of Warwick
spectroscopists discovered that there are extra metallic lines
superimposed on its spectrum, indicating quantities of iron, magnesium
and calcium located in a ring around the star extending out about 1.2
solar radii or 800,000 km. It is suggested that a fairly large
object, like an asteroid, may have approached too close to the star
and been torn apart by the powerful gravitational tides, the ring of
rubble being then evaporated by radiation from the white dwarf.


LOW-MASS PLANET FOUND
BBC News

An international team of astronomers has found the least-massive
planet yet detected outside our Solar System. The planet has five
times the Earth's mass and is 25,000 light-years away towards the
centre of the Milky Way, orbiting a red dwarf star. The discovery was
made by a method called micro-lensing. Named OGLE-2005-BLG-390Lb, the
planet takes about 10 years to orbit its parent star. The scientists
say it probably has a rocky core and perhaps even a thin atmosphere,
but its large orbit and cool parent star mean that it is a very cold
world; its predicted surface temperatures is -220 C. It may therefore
resemble a more massive version of Pluto.


BRIGHTEST SUPERNOVA DISCOVERY
New Scientist

A supernova intrinsically two to three times brighter than any
previously recorded has been observed, and its characteristics suggest
that it did not form like others of its class. It appears to have
been forged in a collision between two stars, adding fuel to a debate
about what causes the type Ia explosions that are a crucial tool in
cosmology.

The prevailing view of type Ia supernovae is that they result from a
white dwarf that slowly accretes matter from an ordinary companion
star. Eventually the white dwarf reaches a mass threshold called the
Chandrasekhar limit, triggering an explosion that completely destroys
it. But some astronomers have argued that type Ia's are actually due
to two white dwarfs merging. The combined mass of the two objects is
above the Chandrasekhar limit, leading to the explosion. Evidence for
that hypothesis came from supernova 2002ic, which had some character-
istics of type Ia's, but unlike others of its type its spectrum also
showed clear signs of hydrogen. Some researchers said that that could
be explained by a white dwarf colliding with the core of a red giant
star; others claimed that 2002ic was a disguised type II supernova
such as occurs when a massive ordinary star collapses to form a
neutron star or a black hole.

Three other supernovae with characteristics similar to those of 2002ic
have since been found. Now, a fourth has been detected, and it offers
the best evidence yet for the merger picture, at least for some type
Ia's, according to a new study led by Eran Ofek of Caltech. The
supernova, called 2006gy, was discovered on 2006 September 18 and
appears to have been about three times brighter than any previously
observed stellar explosion. Unlike the other unusual type Ia's, such
as 2002ic, the September supernova has been traced to a galaxy
dominated by old stars. The researchers argue that it was not a type
II event, because that involves a massive star that has a very short
lifetime and must therefore have been newly formed.




Bulletin compiled by Clive Down

(c) 2007 the Society for Popular Astronomy


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