The SOCIETY for POPULAR ASTRONOMY
Electronic News Bulletin No. 182 2005 September 18
Here is the latest round-up of news from the Society for Popular
Astronomy. The SPA is Britain's liveliest astronomical society, with
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Philip's title see the end of this bulletin.
LATE AUGUST DAYLIGHT FIREBALL
By Alastair McBeath, SPA Meteor Section Director
A lone sighting of an especially brilliant fireball in full daylight has come
through from the Bristol area, seen around 18:55 UT on August 30-31.
Additional reports of this event, or any other fireballs (meteors of
magnitude -3 or brighter), are always welcomed by the Section. For
details of what to report and where to, see the "Fireball Observing" page
off the SPA Meteor homepage at:
PERSEIDS 2005 - PRELIMINARY RADIO ANALYSIS
By Alastair McBeath, SPA Meteor Section Director
Perseid results of all kinds have continued to come through to the Section
since the report in ENB 181. Unfortunately, there remains a gap in the
visual data over the predicted maximum period, between 17:00-19:30
UT on August 12-13, although the Section's overall Perseid meteor tally
is currently approaching 5500! Radio Meteor Observation Bulletin 145
(for 2005 August; see website http://popastro.c.topica.com/maadZXmabkqOUciD1pRb/
was issued on
September 8, and I carried out a preliminary analysis of this data early
last week, to try to bridge the gap in the visual observations, and to
provide some comments for colleagues attending the International
Meteor Conference in Belgium, which concludes today (September 18;
see http://popastro.c.topica.com/maadZXmabkqOVciD1pRb/ for IMC details). So far,
this radio analysis only
covers the August 11-13 period.
Firstly, many of the radio datasets did not give an especially clear Perseid
maximum signature, with several showing very similar counts on either
August 11 or 13, compared to 12. This is not altogether unusual in normal
Perseid years, but there were also problems with atmospheric interference
of various kinds in some of the results. However, a careful inspection of
what seem the more reliably interference-free reports suggests there was
a maximum at some stage between roughly 16:00-20:00 UT on August
12, the majority favouring the interval centred at 18:00 UT +/- 1 hour.
Such a peak could be defined in 9 of the 11 viable datasets, including 5
of 7 from Europe, and 2 of 2 from each of North America and the Far
East. While this conveniently tallied with the predicted maximum timing, in
the absence of any confirming visual results it needs to be taken with a
degree of caution. Even so, it seems likely that this was close to the real
peak, given the different observing circumstances available in the three
There are indications, particularly in the European results, that radio
Perseid activity subsequently may have continued at a good, though
probably below-peak, level through to about the 01:00 +/- 1 hour UT
reporting interval on August 13. This point is not clear-cut, due to the
rising Perseid radiant from Europe. Radio echo counts from North
America and the Far East do not give strong support for it, but the one
set of very long-duration counts from Japan (greater than 20 seconds;
usually taken as indicative of notably bright meteors) suggested increased
rates of such echoes continued from roughly 18:00-20:00 UT on August
12, near this maximum interval.
More Perseid observations - made by whatever technique - continue to
be most welcome, so if you still haven't submitted your results to the
Section, please do so with all speed (reporting details can be found off
the SPA Meteor Section homepage). Many thanks go again to everyone
who has already contributed to our Perseid campaign this year.
FORMATION PROCESS FOR MASSIVE STARS
Harvard-Smithsonian Center for Astrophysics
The most massive stars in our Galaxy are something like 100 times the
mass of the Sun. Some astronomers thought that such massive stars
might form by coalescence, but a new discovery suggests instead that
they develop through the gravitational collapse of a dense core in an
interstellar gas cloud by processes similar to those involved in the
formation of low-mass stars. Astronomers studied a young proto-star
called HW2 which is 15 times more massive than the Sun and located
more than 2,000 light-years away in the constellation Cepheus.
Orbiting the proto-star they discovered a flattened disc of material
containing 1 to 8 times as much gas as the Sun and extending outward
for more than 30 billion miles -- eight times farther than Pluto's
orbit. The existence of the disc provides clear evidence of
gravitational collapse, the same gradual process that built the Sun.
A disc forms when a spinning gas cloud contracts, growing denser and
more compact. The angular momentum of the spinning material forces it
into a disc shape. Evidence in favour of high-mass accretion has been
elusive, since massive stars are rare and evolve quickly.
HUBBLE BEGINS NEW OPERATION
The Hubble Space Telescope entered a new era of scientific operation
when engineers shut down one of the three operational gyroscopes
aboard the observatory. The two-gyro mode is expected to preserve the
operating life of the third gyro and extend Hubble's observations as
far as mid-2008, an eight-month extension. The system maintains
precise pointing of the telescope and was originally designed to
operate on three gyros, with another three in reserve. Three of the
six are no longer functional. When only two gyros are available, the
observatory experiences an 'unsensed' direction. Using Hubble's fine-
guidance sensors, engineers are able to 'fill in' the missing data
normally generated by the third gyro. NASA has said that a Shuttle
servicing mission to Hubble will be considered after two successful
return-to-flight missions. The servicing mission would include
installing new gyros, batteries, and scientific instruments to provide
several more years of observations.
CLUE TO START OF UNIVERSE
Scientists at MIT's Haystack Observatory have made the first radio
detection of deuterium, an atom that is a key to understanding the
beginning of the Universe. The detection of deuterium is of interest
because the amount of deuterium can be related to the amount of dark
matter in the Universe. Because of the way deuterium was created in
the Big Bang, an accurate measurement of it would allow scientists to
set constraints on models of the Big Bang. Also, an accurate
measurement of deuterium would be an indicator of the density of
cosmic baryons, and that density of baryons would indicate whether
ordinary matter is dark and found in regions such as black holes, gas
clouds or brown dwarfs, or is luminous and can be found in stars.
Such information could help scientists who are trying to understand
the very beginning of our Universe.
Until now the deuterium atom has been extremely difficult to detect
with instruments on Earth. Emission from it is weak since it is not
very abundant in space -- there is approximately one deuterium atom
for every 100,000 hydrogen atoms. Also, at optical wavelengths the
deuterium spectral line is very close to the hydrogen line, which
makes it subject to confusion with hydrogen, but at radio wavelengths
deuterium is well separated from hydrogen and measurements may be able
to provide more reliable results.
Recent observations of the D ring have been compared with older images
from the Voyager missions, and show that the structure of the ring has
changed. In particular, one strand of the ring, known as D72, which
was the brightest feature in the D ring a quarter of a century ago,
has become much dimmer and has moved inwards by about 200 km.
FASTEST-SPINNING SOLAR-SYSTEM OBJECT
Astronomers say that the Kuiper Belt Object 2003 EL61 rotates once
every 3.9 hours, which makes it the fastest-rotating object of its
size in the Solar System. Rather than being spherical like Pluto,
the object has a shape much like a squashed rugby ball, its
discoverers say. By knowing its shape, astronomers have been able to
determine that the object is about two-and-a-half times denser than
ice; they have also found that its reflectivity is almost that of
pure snow. 2003 EL61 is big enough for gravity to be the dominant
force governing it rather than its internal structure.
MOST DISTANT STELLAR EXPLOSION
Scientists using the Swift satellite have detected the most distant
explosion yet -- a gamma-ray burst from the edge of the visible
Universe. The powerful burst, probably marking the death of a massive
star as it collapsed into a black hole, was detected on September 4.
The burst came from an era soon after stars and galaxies first formed,
less than a billion years after the Big Bang; it had a redshift of
6.29, which translates to a distance of about 13 billion light-years.
To date, only one quasar has been discovered further away, at a
red-shift of 6.4. Yet whereas quasars are thought to be super-massive
black holes containing the mass of billions of stars, a gamma-ray
burst is supposed to come from a single star.
YOUNG 'SOLAR SYSTEM' FOUND
University of Rochester
A team of astronomers using the Spitzer space telescope has detected
gaps in the dusty discs around two very young stars, which suggests
that gas-giant planets may have formed there. The new findings not
only reinforce the idea that giant planets like Jupiter form much
faster than scientists might have expected, but one of the
gas-enshrouded stars, called GM Aurigae, has some analogies to our own
Solar System. At a mere 1 million years of age, the star possibly
indicates how our own world may have come into being. GM Aurigae is
like a much younger version of our Sun, and the gap in its disc is
about the same size as the space occupied by our own giant planets.
Newly formed planets are postulated to exist within the clearings that
they are supposed to have scoured out in the discs around GM Aurigae
and another star, DM Tauri. The discs have been suspected for several
years to have central holes that might be due to planet formation.
The new data, however, reduce the doubt, because the gaps are so
empty and sharp-edged that planetary formation is quite the most
reasonable explanation for their appearance.
PLUTO MAPPED BY HUBBLE
Astronomers have produced a new colour map of Pluto from images from
the Hubble telescope. The map shows areas likely to be covered with
methane frost and a bright spot perhaps made of frozen carbon
monoxide. Other areas are thought to be dirty water-ice, nitrogen
frost and possibly other things. NASA says that the primary launch
window for the 'New Horizons' mission to Pluto runs from 2006 January
11 to February 14. If it is launched within that window, it will pass
close to Jupiter for a 'gravity assist' and arrive at Pluto in 2015.
An accurate measurement of Charon's radius and density were obtained
from observations made during the moon's occultation on July 11.
Astronomers used the data from that event to tie down the radius of
Charon to 602.5km, plus or minus one kilometre -- the most precise
figure yet obtained for its size. Previous observations had given a
lower limit for Charon's size, but could not say how big it might be.
>From the new radius it is possible to determine a density for Charon
of 1.73 (plus or minus 0.08) grams per cubic centimetre.
European astronomers have discovered a quasar without a detectable
home galaxy. The team studied 20 relatively close quasars (a mere
five billion light years away), drawing on data from both the Hubble
telescope and the VLT. In 19 of the 20 cases, they found that the
quasar was, as expected, sited at the centre of a massive galaxy, but
in the twentieth case no host could be seen. Instead, the astronomers
observed that nearby there was a star-forming galaxy showing signs of
a recent collision, and there was a cloud of gas about 2,500 light-
years across just next to the quasar. However, the researchers note
that observing the host galaxy of a quasar is often challenging work
because the quasar completely outshines the host, so all that they can
really say about the twentieth quasar is that any host galaxy must be
a good deal fainter than normal.
NEW VIEW OF CERES
The Washington Post
For years astronomers have found Ceres, the largest asteroid, to be
practically featureless, but now a team of researchers using Hubble has
obtained images in some detail. The team tracked Ceres through its
full nine-hour rotation, and were able to follow a bright spot as it
was carried round the asteroid, enabling them to determine the
position of its polar axis.
STOLEN EQUIPMENT PLEA
The brass tube and finder have been stolen from Richard Baum's 4.5-inch
refractor. The main optics are safely in the house and are
unaffected, but of course unusable without the tube. The cast-iron
pier, equatorial head and driving clock all by Cooke of York (c 1895)
are always out of doors but are still in place.
Obviously minus the optics the tube is of no use to anyone; still, it
leaves Richard without a telescope which he valued very much and which
over half a century he has used in his observations of the Moon and
planets. The telescope is of great sentimental value to Richard and
if members can help him in any way to recover it, it would be much
appreciated. The tube is inscribed on its brass plate 'Adjusted by
Broadhurst & Clarkson'. If anyone does get any information, please
contact Richard Baum on 01449 761950.
PHILIP'S NEW TITLES:
To be published this month: a brand-new, fully revised edition of Sir
Patrick Moore's Atlas of the Universe, updated to include new images
from the Cassini spacecraft and Huygens probe, the Hubble Space
Telescope, the Very Large Telescope and Mars Express. Â£25.00.
Philip's Astronomy Dictionary has been completely updated to include
more than 1000 A--Z entries, which cover the stars and planets,
galaxies and cosmology, amateur astronomy and professional
observatories, space exploration, famous astronomers, scientific
terms, theories and much more. Â£9.99.
Coming in October: the 4th edition of Philip's Pocket Star Atlas by
John Cox, expanded and revised with full-colour diagrams and
photographs, dates for eclipses, meteor showers and optimum observing
periods for the planets until 2020. Â£4.99.
For more information on those and other Philip's titles please visit
www.philips-maps.co.uk or call 020 7644 6935 for a catalogue.
Bulletin compiled by Clive Down
(c) 2005 the Society for Popular Astronomy
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