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The SOCIETY for POPULAR ASTRONOMY
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Electronic News Bulletin No. 211 2006 December 24
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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
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/maafuppabvzDUcixLLVb/



URSID OUTBURST - INITIAL THOUGHTS
By Alastair McBeath, SPA Meteor Section Director

Very limited amounts of data were available on the Ursid peak by
midday on December 23 (the peak was due on December 22-23; the
updated prediction was given in the Special ENB of December 19),
including my own visual reports, plus some comments from Belgian
watcher Michel Vandeputte and two radio observers, posted on the
Meteorobs e-mailing list (see:
http://popastro.c.topica.com/maafuppabvzDVcixLLVb/ From
these it seems stronger activity did happen from the shower after all.
The visual data suggests a possible Ursid maximum in the hour centred
around 18:35 UT, when Zenithal Hourly Rates (ZHRs) may have
reached 45-55 or so, though this value is very preliminary only, and
is liable to be amended as more results arrive. Activity seemed notably
lower near the ~19:27 UT Lyytinen-Nissinen peak prediction time as
far as the observations allow, but if there were many faint meteors
then, sky conditions could have hidden them. Peter Jenniskens of the
NASA SETI Institute had also suggested there might be a broad
filament of Ursid dust present for some hours surrounding the normal
peak interval, and this may be what contributed to the observed
rates. This broad filament was predicted as possibly reaching a
maximum at about 17:38 UT, with ZHRs of ~40, and generally
brighter meteors. More meteor data from December 22-23 would
be extremely welcome, whenever it was made. The Section's
homepage at:
http://popastro.c.topica.com/maafuppabvzDWcixLLVb/ has details of what
to
send and where to.


GEMINIDS - EARLY NEWS
By Alastair McBeath, SPA Meteor Section Director

First reports suggest the Geminid maximum probably arrived about
as expected, most likely in UK morning daylight of December 14 (as
anticipated in ENB 209), although information to the Section has been
rather scant so far, and Britain seems to have done pretty poorly with
some unhelpfully stormy weather right across the likely better nights
here. Positive reports reaching us directly or via the SPA Forum have
come from: "Aspicio Astrum" (unknown location), "barf" (North
Yorks), Mike Clarke (unknown location), Tim Cooper (South Africa),
Dave "Hampshire Astronomer" (Hants), Leslie Ewan (Midlothian),
"jeremy1133" (Bavaria, Germany), Tony Markham (Staffs), "moonie"
(southern England) and the Director (Northumberland). Many thanks
go to everyone involved.

Too few observations are available yet from near the probable peak
to estimate best ZHRs, but the experimental International Meteor
Organization's (IMO's) "live" Geminid graph, at
http://popastro.c.topica.com/maafuppabvzDXcixLLVb/ , suggests activity
probably
reached something near the normal 120 or so, probably around 11h
UT on December 14. Even in cloud-struck Britain, sometimes quite
healthy Geminid rates could be seen in gaps, and some of the several
fireballs reported from December 11-12 (see below on these) may
have been Geminids. Further Geminid results would be gratefully
welcomed.


DECEMBER FIREBALLS
By Alastair McBeath, SPA Meteor Section Director

Following the excitements of the late November fireballs reported last
time, another bright event occurred around 18:50 UT on December
6-7 as spotted from the West Midlands, but it was December 11-12
which provided most interest, with at least four significant events
reported till now, two from six sites each. Lone sightings are in of
bright events around 18:30 and 22:38 UT that night, seen from
Derbyshire and north-east England respectively. The first of the multi-
station meteors was a magnitude -3/-5 or brighter one at ~17:16 UT,
reported from places in East and South Yorkshire, Lancashire,
Shropshire and Nottinghamshire. A preliminary analysis indicates it
may have been moving roughly east to west across northern England,
possibly over Yorkshire-Durham to Lancashire-Cumbria, and perhaps
ending out over the Irish Sea. The second multi-station event was
at ~22:56 UT, perhaps in the magnitude -8/-12 range, and was
apparently trending generally north to south, probably over the Irish
Sea, but possibly ending over west Wales or the seas nearby. It was
observed from places in Lancashire, Greater Manchester, Cheshire,
Birmingham and Essex. Comments from some of the lucky observers
can be found on the SPA's Observing Forum, at:
http://popastro.c.topica.com/maafuppabvzDYcixLLVb/ Any of
the three earlier meteors may have been Geminids, but this has not
been established as yet. The 22:56 one cannot have been a Geminid
however, and looks to have been a fine, very bright sporadic on the
information now.

Since then, more fireball reports have arrived on a magnitude -10/-15
or so meteor around 22:45-23:00 UT on December 15-16 (seen from
North Wales and the West Midlands), and at ~18:30 UT on
December 17-18 (possibly spotted by two witnesses in East Sussex
and Lincolnshire).

Any other fireball sightings (meteors of magnitude -3 or brighter) from
the UK or close-by would be welcomed by the Section. The essential
information to report can be found via the "Fireball Observing" page at:
http://popastro.c.topica.com/maafuppabvzDZcixLLVb/ .


LEONIDS - RADIO RESULTS AND MORE
By Alastair McBeath, SPA Meteor Section Director

The arrival of November's Radio Meteor Observation Bulletin (number
160; see http://popastro.c.topica.com/maafuppabvzD0cixLLVb/ plus earlier
comments from other
observers, have allowed an examination of the radio meteor behaviour
of the Leonids since the shower update in ENB 210. There was no
clear evidence for a peak on November 17 around 21h UT (the
expected time for the "normal" maximum), but the shower seemed
definitely present in data from November 17-19 inclusive, often at
an apparently quite similar level. Activity was generally somewhat
better in most of the viable datasets on November 19, though not all
systems agreed, and the difference to the other dates was often
marginal. Just one dataset gave an unequivocally strong response
around 04h-06h UT on November 19, especially so between 05h-
06h, while there was no obvious peak at all for the vast majority of
systems. The problem is complicated as for the European stations
located best to catch the expected peak's timing, the likely stronger
maximum coincided with the radiant's most favourable radio-
detectability, and there was no consensus between systems which
recorded different types of meteor echoes as to when any of the
"sub-peaks" detected on November 19 occurred beyond this. This
seems to infer that there was no particular size or mass distribution
of the particles involved around the visual maximum between 04h-05h
UT then, or at least, not one that registered by radio clearly.

The radio observers included: Enric Fraile Algeciras (Spain), Orlando
Benitez (Canary Islands), Mike Boschat (Nova Scotia, Canada), Jeff
Brower (British Columbia, Canada), Gaspard De Wilde (Belgium),
David Entwistle (England), Valter Gennaro (Italy), Ghent University
(Belgium), Patrice Guerin (France), Cristian Negru (Romania), Stan
Nelson (New Mexico, USA), Paul Nicholson (England), Sadao
Okamoto (Japan), Mike Otte (Illinois, USA), Jean-Louis Rault
(France), Andy Smith (England), Dave Swan (England), Istvan
Tepliczky (Hungary) and Felix Verbelen (Belgium).

The IMO's Video Commission report for November, issued via the
IMO-News e-mailing list on December 13, also suggested inconclusive
findings of somewhat heightened Leonid activity throughout November
18-19, without a clear indication of an especial peak, albeit weather
conditions meant only two of the 22 European systems were able to
cover throughout the predicted stronger peak time. However, the
advice from the Visual Commission is that the experimental "live"
Leonid graphs at http://popastro.c.topica.com/maafuppabvzD1cixLLVb/ ,
should now
be regarded as showing the definitive preliminary IMO findings,
suggesting a peak ZHR of ~70-80 was achieved at approximately
04:40-04:50 UT, with rates at or above half the maximum value from
very roughly 03:45-05:30 UT (the start and end are not very clearly
defined in the available data). This is much as the SPA results have
shown since our first report was published in ENB 209. Further data
received by the SPA since has confirmed those initial findings, with
mean ZHRs of ~50-60 in the hour centred at 04:45 UT on November
19. Fresh visual results since ENB 210 have arrived from Howard
Hendrix (California, USA) and Tom McEwan (Spain). One British
observer Clive Rogers has some interesting Leonid meteor images
posted on his webpage now too. See:
http://popastro.c.topica.com/maafuppabvzD2cixLLVb/ .

As before, fulsome thanks go to every one of our Leonid contributors.
All results still unsubmitted on the shower would be welcomed, the
sooner the better.


OVER-MASSIVE STAR IN NGC 6357 IS REALLY THREE
ESA

The open star cluster Pismis 24 lies at the heart of the emission
nebula NGC 6357 in Sagittarius, about 8000 light-years away.
The brightest object in the cluster is designated Pismis 24-1.
It was once thought to have a mass as much as 200 to 300 solar masses.
That would not only have made it by far the most massive star known in
the Galaxy, but would have put it considerably above the currently
believed upper mass limit of about 150 solar masses for individual
stars. However, Hubble images of the star show that it is really two
stars orbiting one another, and spectroscopic observations by
ground-based telescopes further reveal that one of the stars is
actually a tight binary that is too compact to be resolved even by
Hubble. The estimated mass for Pismis 24-1 is therefore to be divided
among the three stars; although the stars are still very massive, the
theoretical mass limit is no longer infringed.



EUROPEAN EXTREMELY LARGE TELESCOPE
ESO

ESO's governing body has agreed to proceed with detailed studies for
the European Extremely Large Telescope. The study, with a budget of
57 million euros, may make it possible to start in 2010 the
construction of an optical/infrared telescope with a diameter around
40 m. It is provisionally dubbed E-ELT, for 'European Extremely Large
Telescope', and astronomers hope to have it made by 2017. The chosen
design, estimated to cost around 800 million euros, involves a 42-m
mirror composed of 906 hexagonal segments, each 1.45 m in size, while
the secondary mirror is as large as 6 m in diameter. The site of the
E-ELT is not yet selected, but a decision is expected by 2008.


MOUNTAIN RANGE ON TITAN
BBC News

The Cassini spacecraft has discovered the highest mountains yet
recognized on Titan. The range is about 150 km long, 30 km wide and
about 1500 m high. The feature was identified by the probe on a
recent pass, from a combination of radar and infrared data. The
mountains lie south of the equator and it is thought that the range is
as hard as rock, but made of icy materials. The mountains appear to
be coated with layers of carbon-rich material that may be methane
'snow'.


MANY PLANETARY NEBULAE DISCOVERED
Anglo-Australian Observatory

Using the UK Schmidt Telescope at Siding Spring an international team
of astronomers conducted a seven-year survey of the part of the Milky
Way visible from Australia. The study found 900 new planetary nebulae
in our own Galaxy and almost 500 more in the neighbouring Large
Magellanic Cloud -- more than had been discovered in the past 100
years. They also found much fainter examples, planetary nebulae in
much later stages of evolution, than had been seen before.


COMET DUST ANALYSED
Science Daily

An international team of scientists has examined the first samples
brought to Earth from a comet. The samples consist of dust collected
from the Comet Wild 2 by the Stardust spacecraft and returned to
Earth. They have proved to contain a wide variety of minerals, as
well as organic, i.e. carbon-containing, materials. Some of the
minerals and organics look similar to those found in primitive types
of meteorites, but there are also some materials not seen in
meteorites. The analysis has confirmed that the early Solar System
was a violent place in which dust and gas underwent considerable
mixing while the Sun and planets were still in the process of
formation. The scientists reported that, even though the comet formed
in the cold outer reaches of the Solar System, it contains high-
temperature minerals that must have formed much closer to the Sun.
In addition, because the samples contain mixtures of high- and
low-temperature materials, the researchers said that they were
confident that the material had been 'stored', largely unchanged,
since it gathered together to form Comet Wild 2 more than 4.5 billion
years ago at the birth of the Solar System.


RADAR REVEALS SUB-SURFACE CRATERS ON MARS
Science Daily

Recent studies made by radar suggest that ancient impact craters lie
buried beneath the smooth, low plains of Mars' northern hemisphere.
The Mars Express probe has a radar system which transmits radio waves
that pass through the Martian surface and are reflected by sub-surface
features whose electrical properties contrast with those of the
materials that buried them. The findings throw light on the question
as to why Mars shows a striking difference between its northern and
southern hemispheres. Almost the entire southern hemisphere has
rough, heavily cratered highlands, while most of the northern
hemisphere is smoother and lower in elevation.

Since the impacts that cause craters can happen anywhere on a planet,
areas with fewer craters are generally interpreted as younger surfaces
where 'geological' processes have erased the impact scars. The
abundance of craters buried beneath Mars' northern plains indicates
that the underlying crust is extremely old, perhaps as old as the
heavily cratered highland crust in the southern hemisphere, but it has
been buried first by vast amounts of volcanic lava and then by
sediments thought to have been carried by episodic flood waters and
wind.


UNIVERSE'S FIRST OBJECTS
NASA

New observations from the Spitzer space telescope suggest that
infrared light detected in a preliminary study originated from clumps
of the very first objects of the Universe. The observations are of
the cosmic infrared background, a diffuse light from the early epoch
when structure first emerged. Some of the light comes from stars or
black-hole activity so distant that, although it originated as
ultraviolet and optical light, its wavelengths have been stretched to
infrared wavelengths by the expansion of the Universe. Other parts of
the cosmic infrared background are from light that has been absorbed
by dust and re-emitted as infrared radiation. The analysis, which was
performed on five regions of the sky, involved accounting for the
contributions from all foreground stars and galaxies, and studying the
fluctuations in intensity of the relatively diffuse remaining infrared
light. It seemed necessary to postulate a clustering of objects to
produce the observed light pattern. If the objects are stars, then
the observed clusters might be the first mini-galaxies, containing a
mass of less than about one million suns. The Milky Way galaxy has a
mass of the order of 100 billion Suns and may have been formed when
mini-galaxies like the objects that Spitzer may have seen may have
merged.



Bulletin compiled by Clive Down

(c) 2006 the Society for Popular Astronomy


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