It is currently Wed Nov 20, 2019 8:25 pm

Post new topic Reply to topic  [ 1 post ] 
Author Message
PostPosted: Sat Dec 03, 2005 9:04 am 
Site Admin

Joined: Fri Dec 03, 2004 11:24 am
Posts: 4376
Location: Greenwich, London
Electronic News Bulletin No. 184 2005 October 16

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 at
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

Philip's, a publisher of astronomy books and planispheres for the
amateur astronomer, is sponsoring this bulletin. For information on
certain Philip's titles see the end of this bulletin.

By Alastair McBeath, SPA Meteor Section Director

Unexpected bright meteor activity has been reported from October 5-6,
particularly during the pre-midnight UT hours. Details from Finnish and
German video results posted on the IMO-News e-mailing list
(International Meteor Organization; see have
suggested this originated from a sharp radiant at RA 10h48m, Dec +79
degrees (near the UMi-Dra border, around 10 degrees from Polaris on
the line to the "Pointers" - Alpha and Beta UMa - in the "Plough"
asterism). The meteors were of about medium speed (inferred geocentric
velocities ~45 km/sec), and bright (mean video magnitude from 7
meteors recorded in Germany was -0.5, compared with a mean of +0.1
magnitude from 13 sporadics). The Finnish data indicated two fireballs
reached video magnitude -5 or so.

The activity seems to have been present over Europe between roughly
17h UT and 02h UT, probably peaking around 19h-20h UT on October
5. However, it is worth noting that not all the early video data showed this
possible radiant, while some preliminary radio and visual reports also
posted on IMO-News from that night failed to find anything unusual either.
Even the positive video results implied detected rates of only 2 to 4
meteors an hour from this source in the better periods.

Intriguingly, two bright fireball sightings have reached the SPA Section,
from 22:34 and 01:46 UT on October 5-6. Confirmation of some details
is still awaited on both of these, but it seems possible now that only the
earlier fireball might have originated from this Dra-UMi source.

Any other fireball, bright meteor, meteor watch, video or radio meteor
observations from October 5-6 would be greatly welcomed by the
Section, to investigate this further, whether the continuous watching was
positive or negative regarding the postulated radiant. Details of what to
report from visual watches and fireball sightings can be found off the
meteor homepage, at: .
See also two topics on the SPA Observing Forum, available off the SPA
homepage "Blue fireball Oct
06 2005"
and "Unexpected bright meteor activity, 2005 October 5-6".

Although some workers have suggested a variety of minor shower
radiants may be active in different parts of Draco around early October
before, very few of these have been confirmed independently, and none
fit to the current profile, as their claimed velocities were all significantly
higher or lower than ~45 km/sec. From the details so far, the October
5-6 activity was definitely not related to the Draconid shower associated
with comet 21P/Giacobini-Zinner.

By Alastair McBeath, SPA Meteor Section Director

Speaking of the Draconids, occasionally called the "Giacobinids" from their
parent comet, as mentioned last time, nothing was predicted for them this
year, despite the comet returning to perihelion in early July. The most
likely time for anything to happen was probably between 15h UT on
October 8 to 01h UT on October 9. Analysis results published
electronically on October 14 now indicate an outburst did occur from the
shower despite the earlier pessimism. Radar data from the University of
Western Ontario (UWO) in Canada showed a distinct Draconid peak at
17:00 UT on October 8, lasting around two hours, though the outburst
duration, particularly its end, was somewhat uncertain. The researchers
there suggested, based on various assumptions from previous visual
Draconid outbursts, that the equivalent visual Zenithal Hourly Rates
(ZHRs) might have been around 150.

A preliminary IMO visual analysis posted on IMO-News showed clear
signs that an unexpected outburst had indeed been spotted visually, but
with a much lower ZHR of about 35 +/- 8, at circa 16h UT on October 8.
Whether this represented the true visual peak is not yet clear, as the next
datapoint after ~16h UT was centred at 18:30 UT, by when the ZHR had
fallen to 15 +/- 2, declining thereafter as October 8-9 progressed. More
visual data from nearer the radar peak at ~17h UT will be needed to
investigate this further. IMO-News also had brief details that the outburst
had been detected by one British radio observer so far.

Few early UK observations have reached the SPA Section yet from then
(visual results from George Spalding in Oxfordshire and the Director),
though only the Director spotted a handful of possible Draconids,
between approximately 20:30 and 23:30 UT, implying ZHRs of around 3
or 4, consistent with the early IMO results. Any additional reports would
naturally be extremely welcome!

Jeremie Vaubaillon, also at UWO, has done some rapid calculations on
the Draconid stream, and found that the outburst probably resulted from
material shed by Comet Giacobini-Zinner at its 1946 return. The reason
this had not been considered before was because the particles involved
were mostly too small to produce visual meteors. In turn, this may well
explain why the outburst was found so strongly in the radar results, which
systems are often most sensitive to meteors far below the visual threshold.

By Alastair McBeath, SPA Meteor Section Director

Not wanting the dust to settle, two sightings of a brilliant meteor have
arrived so far from Coventry and Lincolnshire, which happened at 21:25
UT on October 9. The sightings could suggest the event flew high over
the Cheshire-Lancashire area, perhaps somewhere between the Pennines
to over the Irish Sea or north-east Wales, heading roughly south to north,
but these are only very early ideas at this stage.

By Alastair McBeath, SPA Meteor Section Director

Moonlight is very unkind to two of November's main showers this autumn,
but there are still events of potential note due.

The long-lasting pair of minor Taurid showers continue until about
November 25, reaching maxima around November 5 (Southern Taurids,
radiant then centred near RA 03h28m, Dec +13 degrees) and 12
(Northern Taurids, radiant then centred at RA 03h52m, Dec +22
degrees), though the combined effect of both showers is to produce an
almost plateau-like peak between these dates, with combined ZHRs of
~8-10 or so. With little or no Moon for much of this time, and radiants
well on show for most of the night, splendid opportunities are presented
for observers throughout their maximum spell. Possibly increased
numbers of bright to fireball-class Taurids may continue from late
October into the first week of November or so too, in this latest potential
"swarm" return year (see ENB 183). Past evidence suggests this
enhancement could be rather subtle however, so please don't expect a
vast increase in observed, slow-moving, Taurid numbers!

This should be another interesting post-storms return year for the Leonids.
Last year (see ENB 163), ZHRs were around 20-30 consistently
between November 17-20, without an especially strong peak at any
stage. Jeremie Vaubaillon at the University of Western Ontario has
recently noted that a number of very scattered Leonid stream trails lie not
far from the Earth's orbit this year, which the Earth will pass by from
about November 10-25. However, only a small part of one, a stream laid
down by Comet 55P/Tempel-Tuttle at its 1167 return, is likely to be
partially intersected by the Earth, which could produce a, probably
weakly enhanced, peak at 01:10 UT on November 21. The "normal"
Leonid maximum, seen in years when no special activity is due, is
scheduled for about 14:30 UT on November 17. ZHRs for either are
uncertain, but perhaps 20+ again as last year, or possibly a little higher.
Of these two potential peak timings, only the November 21 event favours
Britain, as the shower's radiant, in the "Head" or "Sickle" of Leo, does not
rise till about 23h UT, and reaches a fully usable elevation only after
midnight. The Moon is worse news, full on November 16, and at last
quarter on November 23 (in Leo!), thus it will be beautifully visible
already by Leonid radiant-rise for either maximum. With the possibility of
at least weak activity due to other Leonid stream trails earlier to later in
the month, observers would do well to keep alert on any clear nights
during this time, after midnight. Expect very swift, often trained, meteors.

November's final shower of interest in 2005 is the swift-meteor Alpha
Monocerotids. This is usually a minor shower, active from November 15
-25, with a maximum due this year at about 15:00 UT on November 21.
In most years, their peak ZHR is around 5, but very occasionally, a much
stronger outburst happens, when for a short while, their ZHR rises
dramatically into the hundreds. The most recent such event was in 1995
November. Enhanced rates were seen across Europe then (including in
the UK) for just 30 minutes, and estimated ZHRs peaked at 420 for a
mere five minutes within that time. There is a suspicion that such enhanced
activity may happen at ten-year intervals, hence the particular interest in
following the shower this year. Unfortunately, observing circumstances
could scarcely be worse, with a waning gibbous Moon for the peak,
which rises by mid-evening for Britain, while the shower's radiant (at RA
07h48m, Dec +01 degree), is well on-view only after 23h UT or so. The
peak timing is scheduled to fall best for sites in and around the western
Pacific Ocean anyway, so the chances of detecting something strong from
the UK are very poor. That said, there is still much to confirm about
Alpha Monocerotid outbursts, and it is possible any notable activity may
occur away from the predicted time. Anyone with clear skies on
November 19-20 and 20-21 and wanting to check for this and any
enhanced Leonid rates too, should observe as much sky as possible,
while avoiding facing the Moon.

More details on November's meteor activity, plus what to report of your
observations and where to, can be found off the SPA Meteor homepage.
Good luck, and clear skies!

The Register

The European Space Agency is asking member states to fund a two-year
feasibility study on joining forces with the Russians to build Kliper,
a new people-carrying space plane that will take over missions to the
International Space Station. The Russians have designed the plane as
a replacement for their Soyuz capsules -- which have been in use since
the 1960s -- and are also planning for the post-Shuttle era.
Ministers are to meet at ESA in early December, where they will be
asked for between 30 and 40 million euros. Development and operations
would be likely to cost another 100 million a year. Expensive as that
sounds, the project would give Europe more autonomy in space.

California Institute of Technology

Astronomers have found a moon orbiting the newly discovered Kuiper-
belt object 2003 UB313. It is estimated that 2003 UB313 (dubbed Xena)
is 20 per cent larger than Pluto, and some astronomers claim that it
is the tenth planet. Its distance from the Sun is 97 AU, which makes
it the Solar System's farthest detected object. The moon, 100 times
fainter than Xena and orbiting the planet once a fortnight, was
discovered on 2005 September 10 with the 10-m Keck II telescope. It
is estimated that the moon, nicknamed Gabrielle, is at least one-tenth
of the size of Xena and may be around 250 km across. To know
Gabrielle's size more precisely, the researchers need to know the
moon's composition, which has not yet been determined. Most objects
in the Kuiper Belt are thought to be about half rock and half
water-ice. Since a half-rock, half-ice surface reflects a fairly
predictable amount of sunlight, a general estimate of the size of an
object with that composition can be made, just on the basis of its
distance and apparent magnitude. Very icy objects, however, reflect a
lot more light, and so appear brighter and are accordingly judged to
be bigger, than similarly-sized rocky objects. Astronomers also
observed a small moon orbiting 2003 EL61, the second of the large
newly discovered Kuiper-Belt objects, but no moon was observed around
2005 FY9, the third one.

University of California

There has been doubt as to whether the very powerful explosions seen
as gamma-ray bursts are all produced by the same mechanism. They seem
to come in two varieties -- long ones, which last about 20 seconds,
the short ones, which last a few tenths of a second. Evidence has
mounted that the longer bursts arise in distant galaxies by the
collapse of massive stars, about 30 times the Sun's mass, that run out
of nuclear fuel and collapse into black holes. Now, observations from
the High-Energy Transient Explorer 2 (HETE-2) satellite have provided
evidence that short-duration gamma-ray bursts are caused by the
collision of two compact stars. HETE-2 observed a burst on July 9
that came from the constellation Grus and lasted only one-tenth of a
second; it pinpointed the source and triggered a series of
observations by the Chandra X-Ray telescope and Hubble, as well as by
ground-based observatories. What they found, for the first time, was
a faint, short-lived optical afterglow, which represents the embers
of the explosion which produced the burst. That, in turn, allowed
astronomers to identify the galaxy in which the burst had occurred,
and to measure its distance. To their surprise, it was 'only' one
billion light-years from Earth, instead of the usual 10 billion for
the long bursts.

Haute-Provence Observatory

An international team of astronomers has discovered a new transiting
extra-solar planet. It is around the star HD 189733, which is
only 63 light-years away in the constellation Vulpecula, and at
magnitude 7.7 can be seen in binoculars. It happens to be located
close to the famous M27 'Dumbbell' planetary nebula, well known to
amateur astronomers. The planet HD 189733b was detected by the
combination of two different methods, radial velocities and
photometric transits, with telescopes at Haute-Provence Observatory.
It is one of the few extra-solar planets for which there are
determinations of both the radius (1.26 Jupiter radii) and mass (1.15
Jupiter masses). Its density is comparable to that of Saturn. Its
orbital period is one of the shortest known (only 2.2 days), and owing
to the favourable orientation of its orbital plane it occults its star
at each revolution, producing a decrease in luminosity of 3%, the
deepest occultation of the nine known transiting systems. The planet
is so close to its star (only 3/100 of the Earth--Sun distance) that
its atmosphere must be very hot, several hundred degrees. Attempts
will be made to measure the reflectivity of its atmosphere, its
chemical composition and the rate of evaporation. The light emitted
by the planet itself may even be within reach of interferometry.

BBC Online

Japan's Hayabusa spacecraft, designed to collect a sample from an
asteroid and return it to Earth, has lost the second of the three
reaction wheels that maintain its attitude in space without expending
fuel by using thrusters. The probe has now settled in a 'home
position' about 6.8 km from its target, the asteroid Itokawa, and is
currently using a combination of its two chemical engines and the last
remaining reaction wheel to maintain a stable attitude. Teams are
looking at how to conserve fuel following the unanticipated use of the
engines and are considering whether to make changes to the mission.
Fortunately, Hayabusa has nearly finished mapping the asteroid, and if
controllers stick to their original plan the probe will make two brief
touchdowns on the asteroid in November. Each time it lands, it will
fire a metal pellet into the surface at 300 m/s, after which it will
take off again to collect the dust ejected by the impact. It will
also deploy a small probe called Minerva to the surface of Itokawa.
Hayabusa will begin its return voyage to Earth, with the samples, this
December, and is expected to arrive in 2007 June.

University of Arizona

The reason that a 300-mile-wide patch outshines everything else on
Titan at 5-micron infrared wavelengths is unknown -- it appears not to
be a mountain, a cloud or a geologically active hot spot, say
scientists. The bright spot occurs where Cassini's visible-wavelength
imaging cameras photographed a bright arcuate feature in 2004 December
and 2005 February. Cassini's radar instrument, operating in the
passive mode that is sensitive to microwaves emitted from a planetary
surface, saw no temperature difference between the bright spot and the
surrounding region. That rules out the possibility that the 5-micron
bright spot is a hot spot, such as an active ice volcano. And if it
is a cloud, it's a cloud that hasn't moved or changed shape for three
years, according to ground-based observations made at the Keck
Telescope and with Cassini's visual and infrared mapping spectrometer
during five different fly-bys.


China has launched its second manned spacecraft, with two astronauts
aboard, from the Jiuquan Satellite Launch Centre in the north-western
province of Gansu. In 2003 October, China became the third country
to put a man into space, when Colonel Yang Liwei orbited the Earth 14
times in 'Shenzhou V'.


The extreme environment surrounding the black hole at the centre of
our galaxy is a birthplace for new stars, according to scientists who
have used Chandra X-ray images to study the region around the central
object Sgr A*. Their results challenge theories of star formation,
as they show that stars have formed close to the black hole and
contain a much smaller percentage of low-mass stars than predicted.
This is the first observational evidence for star formation in an
accretion disc around a black hole; massive black holes are usually
associated with violence and destruction, so it seems remarkable that
this one appears to help create new stars, not just destroy them.


Owing to holidays, the next scheduled bulletin will appear on Sunday
November 20th.


Published last 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. £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. £9.99.

New this month: 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. £4.99.

For more information on those and other Philip's titles please visit or call 020 7644 6935 for a catalogue.

Bulletin compiled by Clive Down

(c) 2005 the Society for Popular Astronomy

 Profile Send private message  
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 1 post ] 

All times are UTC

Who is online

Users browsing this forum: No registered users and 2 guests

You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You can post attachments in this forum

Search for:
Jump to:  
Powered by phpBB® Forum Software © phpBB Group