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The SOCIETY for POPULAR ASTRONOMY
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Electronic News Bulletin No. 226 2007 August 5
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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/maahkGEabAmXMcixLLVb/


OCCULTATION OF THE PLEIADES
Jon Harper, Occultation Section

During the early morning of Tuesday, August 7, there is another
wonderful opportunity for astrophotographers to take some good images
when bright members of the Pleiades Open Cluster reappear from behind
the Earth-lit night hemisphere of the waning crescent Moon. The data
given below are for Greenwich first, followed by Edinburgh. They
consists of the UT time of reappearance (don't forget to ADD 1 hour
for BST), followed by the altitude and azimuth of the Moon, and the
Position Angle (PA) of the star's reappearance in relation to the
Moon's limb. Remember, the PA is measured from the Celestial Pole in
an anticlockwise direction around the Moon's limb. Any timings,
reports or graphics would be gratefully received. Please send them to
me at the following e-mail address: jonvran@aol.com

ELECTRA (17 Tauri) m(v) 3.7 00h 47m, 19°, 75°, 214°
00h 56m, 20°, 76°, 222°

CELAENO (16 Tauri) m(v) 5.4 00h 56m, 21°, 76°, 253°
01h 03m, 21°, 77°, 260°

TAYGETA (19 Tauri) m(v) 4.3 01h 06m, 22°, 78°, 284°
01h 11m, 22°, 78°, 293°

MAIA (20 Tauri) m(v) 3.9 01h 21m, 24°, 81°, 252°
01h 28m, 24°, 82°, 259°

ASTEROPE (21 Tauri) m(v) 5.8 01h 23m, 25°, 81°, 291°
01h 26m, 24°, 81°, 302°

Graphics of all these events may be found at the following web
address, by clicking on the name of the star:
http://popastro.c.topica.com/maahkGEabAmXNcixLLVb/


RECENT FIREBALL SIGHTINGS
By Alastair McBeath, SPA Meteor Section Director

After a lull in UK fireball reports during the "rainy season" here
recently
(June to mid July), late July has brought a fresh crop of sightings,
including single-observer events on: July 21-22, ~21:15 UT, a very
bright event from Northants; July 23-24 at 22:16 UT, a magnitude -3
or brighter meteor seen from Hartlepool; and on July 28-29, ~22:55 UT,
a magnitude -8/-10 event spotted from County Durham. Around
22:58 UT on July 31 to August 1, one witness in each of North
Yorkshire and Oxfordshire saw another splendidly bright meteor,
perhaps around magnitude -7/-10. Sighting reports from this object's
Oxon observation, and the July 23-24 event are on the SPA's
Observing Forum. Links to both are given on the Recent Fireball
Sightings webpage, at:
http://popastro.c.topica.com/maahkGEabAmXOcixLLVb/

Assistant Meteor Director David Entwistle has also alerted me to a
brilliant daylight fireball that happened over the NW Balkans and Italy
circa 10:00 UT on July 25. It was of magnitude -20 at best in its two
brightest flashes (full Moon is about magnitude -14, the Sun -26), and
sonic booms were heard afterwards from it. Initial information suggested
hundreds of witnesses in Slovenia, Croatia and Italy had seen it, which
analysts in all three countries are currently examining and collating.
Initial media reports showed several video images of a spectacular
fireball, but these all seem to have been of quite separate, unrelated
events, imaged a lot earlier. If you feel up to testing your Croatian,
try: http://popastro.c.topica.com/maahkGEabAmXPcixLLVb/ for one of the
media reports with an image.
If you prefer English, there are some brief notes, again with the same
image, on the Spaceweather archive webpage for July 31:
http://popastro.c.topica.com/maahkGEabAmXQcixLLVb/

Lastly for today, good luck for next weekend's Perseid maximum!


MARS ROVERS BRAVING SEVERE DUST STORMS
NASA

Having explored Mars for three-and-a-half years on missions originally
designed for three months, the Mars rovers are facing another
challenge in the form of summer dust storms, which for over a month
have affected the rover Opportunity and, to a lesser extent, its
companion, Spirit. However, so far the rovers are showing robust
survival characteristics. The dust over Opportunity has blocked 99%
of direct sunlight, leaving only the limited diffuse sky light to
power it. If the sunlight is further cut back for an extended period,
the rovers will not be able to generate enough power to keep
themselves warm or to operate at all, even in a near-dormant state;
they use electric heaters to keep some of their vital core electronics
warm. Engineers are taking measures to protect them, especially
Opportunity. Spirit, in a location where the dust is currently less
severe, has been instructed to conserve battery power by limiting its
activities.


TINY ASTEROID TRAILING MARS
New Scientist

A small asteroid has been found that travels with Mars as it orbits
the Sun, bringing the total number of such objects to four. The
asteroid, called 2007 NS2, was discovered by astronomers at the La
Sagra Observatory in southern Spain on July 16. On the basis of its
brightness, it is estimated to be about 1 km across. It is 60° behind
Mars in its orbit, occupying a spot called L5. It shares L5 with two
other objects, while a fourth object orbits 60° ahead of Mars at the
point called L4. The 'Langrangian points' L4 and L5 are places in
whose vicinities a small body may be stably confined by the combined
gravities of a planet and the Sun.

Mars is one of three planets known to have such objects, known as
Trojans, sharing its orbit. About 2200 are known to accompany
Jupiter, and a handful have been discovered in Neptune's orbit as
well. After the discovery of 2007 NS2, astronomers found the asteroid
in images from the Arizona-based LONEOS and LINEAR near-Earth-object
surveys dating back to 1998, and were thereby enabled to calculate a
more precise orbit for it. The Earth has no known Trojans, but there
are a few so-called Earth co-orbital asteroids. They have corkscrew
orbits, slowly looping around the Earth while following its orbital
motion around the Sun. Such configuration is unstable, so the objects
are only temporary companions to Earth. One of them, called 2005 GU9,
about 200m across, has been looping around for 500 years, but will
eventually drift away.


ACTIVE GALACTIC NUCLEI
Chandra X-Ray Center

Supermassive black holes have been discovered to grow more rapidly in
young galaxy clusters, if we accept new results from the Chandra X-ray
observatory. Scientists surveyed a sample of clusters and counted the
fraction of galaxies with active galactic nuclei (AGN, thought by some
astronomers to be rapidly growing supermassive black holes). Four
clusters at large distances, seen as they were when the Universe was
about 58% of its current age, contained about 20 times more AGN than
in less-distant clusters, at 82% of the Universe's current age. AGN
outside clusters are also more common when the Universe is younger,
but only by factors of two or three over the same age span. It is
plausible that, early in the history of the Universe, galaxies
contained a lot more gas that could fuel star formation and black-hole
growth than galaxies in clusters do today.


MOLECULES IN OUTFLOW FROM SUPERGIANT STAR
Nature

VY Canis Majoris, one of the most luminous infrared objects in the
sky, is an old star about 5,000 light years away. It is half a million
times more luminous than the Sun, but is relatively cool and therefore
shines mostly in the infrared. It truly is 'supergiant' -- 25 times as
massive as the Sun and so big that it would fill the orbit of Jupiter
-- but it is losing mass so fast that in a million years it will be
gone. It has already blown away a large part of its atmosphere,
creating a circumstellar envelope that contains about twice as much
oxygen as carbon. University of Arizona astronomers identified a
number of molecules in the outflow from the star. Among them are
sodium chloride, phosphorus nitride, HNC which is a variant form of
hydrogen cyanide, and an ionic form of carbon monoxide (HCO+).
Material returned to the interstellar medium by dying stars like VY
CMa is likely eventually to collapse into denser clouds, from which
another generation of stars is formed.


SPACE MOLECULE FOUND
NRAO

Astronomers using data from the Green Bank radio telescope have
found negatively-charged octatetraynyl, a chain of eight carbon atoms
and one hydrogen atom, in the envelope of gas around an old, evolved
star and in a cold, dark cloud of molecular gas. In both cases, the
molecule had an extra electron, giving it a negative charge. About
130 neutral and about a dozen positively-charged molecules have been
discovered in space, but the first negatively-charged molecule was not
discovered until late last year, and the new one is the third and the
largest.


SATURN SATELLITE NAME CHANGE
IAU

The IAU has voted to change the spelling of the name of Saturn XLIV
from 'Hyrokkin' to 'Hyrrokkin'!


APOLLO'S LUNAR IMAGES GO DIGITAL
Arizona State University

Nearly 40 years after man first walked on the Moon, the complete
photographic record from the Apollo project will be accessible both to
researchers and the general public online. Created from the original
flight films, the archive will includes photos taken from lunar orbit
as well as from the surface. The reason that the original Apollo
images have been so seldom accessed is that they are literally
irreplaceable. Between 1968 and 1972, NASA made sets of duplicate
images after each Moon mission came back to Earth, placing the
duplicate sets in various scientific libraries and research facilities
around the world. It is those copies (and subsequent copies of them)
that scientists and the public have seen; inevitably, they are not as
good as the originals, which have remained in deep-freeze storage at
the Johnson Space Center.

The Apollo digitising project has scanned the original flight films
with high resolution in both linear terms (5-micron pixels, fine
enough to show the photographic grain) and in intensity (14-bit,
giving 16,000 shades of grey). The most detailed images from lunar
orbit show rocks and other surface features about 1 metre across. The
project will take about three years to complete and will scan some
36,000 images. They include about 600 35-mm frames, roughly 20,000
Hasselblad 60-mm frames (colour and monochrome), more than 10,000
mapping-camera frames, and about 4,600 panoramic-camera frames.


NEXT BULLETIN

Owing to holidays, the next scheduled bulletin will be not be issued
until September 2.



Bulletin compiled by Clive Down

(c) 2007 the Society for Popular Astronomy


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