Society for Popular Astronomy

[joe]

***********************************
The SOCIETY for POPULAR ASTRONOMY
***********************************
====================================================
Electronic News Bulletin No. 273 2009 August 23
====================================================

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
visiting http://www.popastro.com/


PERSEID MAXIMA - A FIRST ANALYSIS
By Alastair McBeath, SPA Meteor Section Director

Preliminary results from near the expected Perseid maximum so far
have found the shower produced three abnormally strong peaks this
year in a rather complex activity pattern, not quite like any of the
predictions (which were discussed in ENB 271, archived at
http://snipurl.com/qrqwd ). Bright moonlight, as anticipated, has caused
problems in interpreting the visual data, and the computed Zenithal
Hourly Rates (ZHRs) below should be treated more as probable
guides than absolute values, because of uncertainties in correcting to
allow for the sometimes tricky sky conditions.

Although the weather, and the timings of the maxima, were generally
unhelpful for watchers in Britain, the Section has been very fortunate in
enjoying considerable support from elsewhere, particularly in the form
of a large amount of visual data from members of the North American
Meteor Network (NAMN; http://www.namnmeteors.org ), very kindly
provided, within at times hours of his receiving it, by NAMN leader
Mark Davis. Contributions from people reporting on the SPA Forums
(see the main Perseids topic at http://snipurl.com/qrrjn ) and on the
UK Weather World's Space Weather Forum (beginning at
http://snipurl.com/qrrkx ) have also been included here, along with notes
from detailed discussions regarding his own radio and video results,
and the radio results of others across the world, from long-standing
Section correspondent Jeff Brower. The full list of observers active
from August 10-14 to report-in to date was as follows, where "I" means
still-imaging, "R" radio, "Vi" video and "V" visual results were provided
by that individual.

"Adam D" (Scotland; V), Salvador Aguirre (Mexico; NAMN; V), "akkan"
(England; V), "Allenh" (England; V), "Bazmundo" (England; V), Mike
Boschat (Nova Scotia, Canada; NAMN; V), Pat Branch (Texas, USA;
NAMN; V), Jeff Brower (British Columbia, Canada; R + Vi), "Bushy"
(England; V), Maggie Daly (England; V), David Entwistle (England; R),
Pam Foster (Scotland; V), "Goatherd" (England; V), Bill Haddon
(California, USA; I + V), "Halo" (England; V), Michael Hayes (Northern
Ireland; V), Alan Heath (England; R), "jcdorset" (England; I + V), "JohnM"
(England; I), "Jonesy_1" (England; V), Pete Lawrence (England; I),
"louise79" (Northern Ireland; V), Robert Lunsford (California, USA;
NAMN; V), "markh" (England; I + V), Felix Martinez (Virginia, USA;
NAMN; V), Paul Martsching (Iowa, USA; NAMN; V), Alastair McBeath
(England; V), Bruce McCurdy (Saskatchewan, Canada; NAMN; V),
Martin McKenna (Northern Ireland; I + V), "MikeMS" (France; V), Jane
Mills (England; V), "OCEANSTORM" (Scotland; V), David Oesper
(Wisconsin, USA; NAMN; V), "OkarcheDave" (Oklahoma, USA; V),
Robin Scagell (England; I + V), Leo Stachowicz (England; I), "starlifter"
(Scotland, V), Wesley Stone (Oregon, USA; NAMN; V), William
Watson (New York, USA; NAMN; V).

Information from the International Meteor Organization's (IMO's) "live"
Perseids results webpage (at http://www.imo.net/live/perseids2009 ),
though still liable to change, has indicated a first visual maximum over
North America at around 08:00-08:15 UT on August 12, when ZHRs
were ~160 briefly, with rates of just 50 or so less than an hour before
this. Activity seemed to drop for a time afterwards, to perhaps as low
as ~45 close to 09:10, before building again in the UT afternoon, to be
somewhat variably between 130-170 from about 14:25-19:50 UT. It is
not clear whether an apparent drop to a ZHR of ~105 at ~18:00,
followed by a dramatic rise to almost 200 by 18:19 UT, was a real
feature, or simply due to a lucky observer or two under difficult sky
conditions. Part of this protracted second peak interval coincided with
the predicted "normal" Perseid maximum for 2009. Its activity was
greatly above that thought likely then though! Activity dropped and
levelled-off fairly consistently after this overnight for Europe on August
12-13, with ZHRs of ~70-100 in general, rather better than might have
been supposed. As morning broke for western Europe, North American
observers found rates were rising once more towards a third maximum,
not quite as sharp as the first seen there, near 06:30 UT on August 13,
when ZHRs may have crested 225 for a short time, before dropping
swiftly away to ~145 by 06:40. Activity of about 190-200 preceded this
from circa 05:50 UT, with a surrounding period of increased ZHRs,
~100-150, lasting from 04:00-08:00. Rates had declined back to
normal levels before European nightfall on August 13-14, as far as
conditions then allowed.

As might be expected, the SPA visual results showed a similar pattern
to this for the two North American peaks, and the European activity on
August 12-13. Thanks to the NAMN results, it was possible to define
ZHRs at 15-minute intervals for part of the time on both August 12 and
13, closest to these two maxima. A very striking peak (ZHR ~220) was
apparent in the 15-minute interval beginning at 08:00 UT on August 12,
bracketed by ZHRs of 130+ from 07:30-08:30. However, although
activity dropped below 60 in the 08:30-08:45 UT interval it had risen
again to ~140 by 08:45, remaining around 120 till 09:15, and falling
only gradually thereafter to be ~65 by 10h. The SPA data sample is
smaller than the IMO one of course, plus there are caveats regarding
the calculation problems, but it is intriguing that radio meteor
observations from Europe and North America showed a clear, strong
to very strong, spike in echo counts around 07h-09h UT. (The radio
data are routinely sorted into one-hour bins, so "09h" means 09h-10h;
the initial radio results are available via the Radio Meteor Observation
Bulletin, RMOB, webpage at http://www.rmob.org/livedata/main.php .)
Furthermore, Jeff Brower commented that this spike seemed to have
shown an excess of longer-duration echoes in his 10-minute data
collection interval over 09:00, than in the data bins to either side of this
time, which may suggest more bright Perseids were present then. His
detailed counts for meteor echo numbers and durations overall
supported the 07h-09h peak, but also indicated good activity was
present after this from 10h UT probably through to 19h, with several
possible maxima, the most strikingly convincing of which was in the
16h UT bin, the strongest such peak Jeff recorded during this year's
Perseids. Of particular note, there was no maximum in the 18h interval,
just declining echo numbers, though the radiant was still favourably-
placed for radio observing at Jeff's site, suggesting the possible visual
peak then in the IMO data was simply an artefact in the analysis after all.

Jeff reported his automated fireball video system recorded 19 fireballs
between 04:25-11:30 UT on August 12, with three of those (~16%)
caught between 08:04 and 08:11, and a fourth at 08:39. Four more
were recorded in another "cluster" between 10:00 and 10:33 UT. On
the following date, the interval from 05h-06:30 UT was especially fruitful,
with six of eleven fireballs between 05:00-11:15 falling in that period,
though not quite so closely bunched as on the previous morning.

British observers who were able to see something of events overnight
on August 12-13 generally seemed to have enjoyed what happened,
which seems a definite reflection of the fact Perseid ZHRs by then were
still very good, somewhere between 65 to 80 in the European SPA
results from 22:30-03:00 UT, though we just missed out on the rapidly
rising rates from ~04h onwards seen so well from North America on
August 13. Our analysis found the strongest peak after then in the 15-
minute interval from 06:00-06:15 UT, when ZHRs topped-out at ~260,
while otherwise mirroring the IMO data. Jeff Brower's radio results
concurred on a peak between roughly 05h-09h UT, with his longer-
duration counts particularly favouring the 06h bin.

Moonlight greatly reduced the number of meteors seen under good
enough conditions for magnitude and train analyses (limiting
magnitude +5.5 or better, cloud cover less than 20%), but the mean
magnitudes corrected for an ideal sky for 289 Perseids and 50
sporadics seen between August 10 to 14 respectively were +2.3 and
+3.7, which are fairly typical values, the sporadics perhaps a little fainter
than normal, but the tiny sample made this unreliable anyway. About
33% of Perseids left persistent trains, which is also about normal.

Very many thanks go to all the observers named above, whose efforts
and swift reactions in reporting so promptly have allowed this amount
of detail to be established already within ten days of the events, making
this period a most dynamic and exciting one. My further thanks go to
Mark Davis and Jeff Brower for quite invaluable help and discussions
during the past two weeks. All further Perseid results would be still most
welcome!


DELTA AQUARID & ALPHA CAPRICORNID ANALYSIS
By Alastair McBeath, SPA Meteor Section Director

Usually in years when the Perseid maximum will be affected by the
bright Moon, visual observers' attention during the summer switches
to the late July maxima from the Delta Aquarids and Alpha
Capricornids. However, as already detailed, they were thoroughly
upstaged by the Perseids despite the Moon this time! Though both
sources are a lot less active than the Perseids, they are always
interesting to watch, particularly because, as recent IMO and SPA
analyses have indicated, the maxima for both tend to be a little
uncertainly-timed, and perhaps each persist for a few days. The
contributing observers from the late July to early August period involved
are listed below, and again the SPA tallies were greatly boosted by
data from the NAMN, courtesy Mark Davis. In addition, late July's radio
meteor results were extracted from RMOB 192 for July 2009 (available
at: http://www.rmob.org ), thoughtfully provided by editor Chris Steyaert.

Enric Algeciras (Spain; RMOB; R), Jeff Brower (British Columbia,
Canada; R - also RMOB), Willy Camps (Belgium; RMOB; R), Mark
Davis (South Carolina, USA; NAMN; V), Gaspard De Wilde (Belgium;
RMOB; R), Bill Godley (Oklahoma, USA; NAMN; V), Roberto Haver
(Italy; NAMN; V), Tony Markham (England; V), Pierre Martin (Ontario,
Canada; NAMN; V), Paul Martsching (Iowa, USA; NAMN; V), David
Oesper (Wisconsin, USA; NAMN; V), Mike Otte (Illinois, USA; RMOB;
R), Jean-Louis Rault (France; RMOB; R), Steve Roush (Arizona, USA;
RMOB; R), Wayne Sanders (British Columbia, Canada; RMOB; R),
Andy Smith (England; RMOB; R), Chris Steyaert (Belgium; RMOB; R),
Enrico Stomeo (Italy; Vi), Wesley Stone (Oregon, USA; NAMN; V),
Dave Swan (England; RMOB; R), Istvan Tepliczky (Hungary; RMOB; R),
Maarten Vanleenhove (Belgium; RMOB; R), Felix Verbelen (Belgium;
RMOB; R), William Watson (New York, USA; NAMN; V).

As noted in ENB 270 (archived at: http://snipurl.com/qrr01 ), the Delta
Aquarid maximum was due around July 28 to 30 (ZHRs ~15-20), while
that of the Alpha Capricornids was expected near July 30 or 31 (ZHRs
~5). There is now a problem for the Alpha Capricornids, because
recent IMO video findings have suggested their radiant overlaps that of
the large Antihelion Source, active simultaneously, and this was the first
year since this was noted that observations of the shower were
possible in moonless skies to check this aspect. Unfortunately,
relatively few Alpha Capricornids were recorded visually. Whether that
meant the shower was unexpectedly inactive this summer, or that there
really was a serious identification problem in separating this source
from the Antihelion, is not clear, but this will be an area needing further
investigation, as the shower had been definitely identifiable in earlier
SPA analyses recently, before the Antihelion Source was determined
as it is presently.

By contrast, the Delta Aquarids gave a clearer maximum, though
without particular definition, between July 28 to 31. There were
suggestions activity may have been highest, ZHRs ~20, on both July
30 and 31, but the data sample was relatively small to confirm this. The
mean magnitudes, corrected for a limiting magnitude +6.5 sky, for 155
Delta Aquarids and 263 July-August sporadics respectively were +2.8
and +2.9, both about average. Perseid activity at the same time gave
ZHRs of ~5-10, with a corrected mean magnitude (but from just 96
meteors) of +2.9. Train populations for the three sources were 11%,
6% and 35%, all much as anticipated.

Interference problems reduced the effectiveness of the radio data
throughout June and July, and interpreting the late July radio meteor
results was no different. The surviving data generally showed the
typically healthy late July echo-counts, with a majority favouring July 28
as showing the better peak during that time. Some also found quite
good activity again on July 30, but the proximity of the southern-sky
radiants to one another makes it impossible to separate activity from
them using forward-scatter radio observations, so the significance of
these potential maxima can only be inferred from the visual analysis.

Once again, my grateful thanks go to all the named contributors above
for their time and trouble. All additional observations from the period
would be equally welcomed!


METEOR SECTION WEBPAGE UPGRADE NEWS
By Alastair McBeath, SPA Meteor Section Director

As perceptive regular visitors to the Section's webpages (homepage
at: http://www.popastro.com/sections/meteor.htm ) will appreciate,
among various minor improvements since the previous note on this
topic in ENB 267, http://snipurl.com/qrsgo , there is a new page with
hints and tips for observers, particularly intended to help newcomers,
part of which used to be on the old "Shelagh's Spots" page, while
during the Perseids the new "Radio Observation of Meteors" page
has gone online too, with information on how to get started in radio
meteor work, probably the most technically-challenging amateur
meteor observing technique. Further changes, to complete the upgrade
to the Section's Internet presence begun back in January, will happen
during the autumn.


METEOR ACTIVITY FOR SEPTEMBER
By Alastair McBeath, SPA Meteor Section Director

Meteorically often seen as August's poor relation, with no major
showers like the Perseids, September has long brought its own brand
of interest with a number of poorly-studied minor showers. Recent IMO
visual and video analyses have revealed a number of significant
problems with the parameters for the three supposedly established
swift-meteor, near-Auriga showers, believed active at times between
late August and mid October, the Alpha and Delta Aurigids, and the
September Perseids. For some time, these showers have been
suspected of simply being (perhaps the more active) part of a series
of poorly-observed sources with radiants around Aries, Perseus,
Cassiopeia and Auriga during the early autumn. Now, this indeed
seems to be the case. Details of the main discrepancies found by the
latest IMO results compared to what was previously thought, and other
notes, are given on the Section's September meteor activity webpage,
http://snipurl.com/qs48o , along with information on the other showers
known to be active during the month.

The Alpha Aurigid maximum is perhaps the more interesting regular
element of these near-Auriga sources. It should fall around September
1 this year, with a waxing gibbous Moon setting between 01h and 02h
UT for British sites then, quite good news, as the Auriga area of sky is
usefully-observable only after 23h UT. Unexpected Alpha Aurigid
outbursts occurred in 1935, 1986 and 1994, which produced ZHRs of
~30-40 (ZHRs are usually ~6 or 7), though none were widely-seen,
while the first predicted outburst was observed in moonlit skies in
2007, yielding estimated ZHRs of ~130 briefly, and was rich in
fireballs (see ENBs 228, http://snipurl.com/qrxuq , and 233,
http://snipurl.com/qryqg ). No similarly strong activity is predicted this
year, but you never know!

Additional near-Auriga sources seem likely to be active during
September as well, including that which produced the unexpected
outburst of swift, bright meteors on 2008 September 9 (see ENBs 253,
http://snipurl.com/qrrpw , and 254, http://snipurl.com/qrrr4 ), perhaps
the formerly-little-known Epsilon Perseid minor shower. Another
possible source from this rough area of sky has been detected only in
radio results so far, especially from 1989, 1990 and 1999, apparently
peaking around September 16 or 17. Weak activity around September
15-16 was found in an SPA radio-meteor analysis of 1993-96
observations which may be related, activity that has been confirmed in
most years since 1996, though its origin is not certain. It may be just
coincidence that two of the better-detected returns occurred in years
ending in "9", and while nothing is anticipated in 2009, it will be
interesting to see if any similar activity repeats this time. Oddly, visual
observers did not report anything unexpected simultaneously in
1989, 1990 or 1999. Some, mostly colloquial, details have appeared
from occasional years on one or more possible weak visual sources
present in mid September since 1991, with radiants somewhere around
Taurus-Perseus-Aries-Orion-Gemini. However, these were based on
very little data, and showed no consensus on radiant positions between
the individual watchers. The waning crescent Moon by mid-month, new
on September 18, should give no problems for post-midnight UT
observing during this September 15-17 period at least.


MARTIAN METHANE NOT UNDERSTOOD
ESA

The discovery some years ago of methane in the Martian atmosphere
was a surprise. Much of the methane in the Earth's atmosphere is of
biological origin, but some is contributed by vulcanism. Methane is
thought to be stable in the Martian atmosphere for around 300 years.
It follows that the observed methane must have been generated within
the last few hundred years. Recently, people at Goddard Space Flight
Center have said that the methane that they saw in 2003 was
concentrated in three particular regions. That showed that it must
have been released so recently that it had not had time to distribute
itself around the planet. Moreover, instead of taking 300 years to
disappear, it had almost entirely vanished by early 2006. Now,
atmospheric physicists have tried to model Mars' climate, but their
models are unable to reproduce the behaviour of the methane.
Something seems to be removing the methane from the atmosphere 600
times faster than the models can account for. That might suggest that
the source must be 600 times more intense than was originally assumed,
which is considerable even by terrestrial standards.


TRIPLE ASTEROID SYSTEM
NASA/Jet Propulsion Laboratory

Radar imaging has shown that near-Earth asteroid 1994 CC, which came
within 2.52 million kilometres of the Earth on June 10, is a triple
system, only the second triple system known in the near-Earth
population. It consists of an object about 700 metres in diameter
that has two smaller bodies, probably at least 50 metres in diameter,
revolving around it. The next comparable Earth fly-by for asteroid
1994 CC will occur in 2074, at a distance of 2.5 million kilometres.


CASSINI DISCOVERS NEW OBJECT IN SATURN'S RINGS
JPL

The Cassini spacecraft has discovered a new object in Saturn's rings.
As the Sun shone onto the rings almost edgewise as the planet neared
its August 11 equinox, Cassini observed the 25-mile-long shadow cast
on Saturn's B ring by a tiny moonlet that is probably about a quarter
of a mile in diameter.


TRACES OF PLANET COLLISION FOUND
NASA/JPL

The Spitzer space telescope has found evidence of a high-speed
collision between two objects orbiting around a young star called
HD 172555, still in the early stages of planet formation. The star
is about 100 light-years away in the far-southern constellation Pavo,
and is considered to be about 12 million years old. Astronomers
believe that two rocky bodies, one at least as big as Mercury and the
other at least as big as the Moon, slammed into each other within the
last few thousand years or so -- very recently by cosmic standards.
The impact destroyed the smaller body, vaporizing huge amounts of rock
and flinging massive plumes of hot lava into space. The collision
would have had to be between substantial bodies and at a high speed
for rock to have been vaporized and melted. It would be a rare event,
but critical in the formation of Earth-like planets and moons. It
might be analogous to the one that has been speculated to have formed
our Moon more than 4 billion years ago, by the collision with the
Earth of a body the size of Mars. Such violence is thought to be a
routine aspect of planet-building. The most popular theory at present
is that rocky planets form and grow in size by colliding and sticking
together, merging their cores and shedding some of their surfaces.
Even though things have settled down in our Solar System today,
impacts do still occur, as was observed only last month after a small
object of some sort crashed into Jupiter.

The infrared spectra taken by Spitzer have been interpreted as
demonstrating lots of amorphous silica, essentially melted glass.
Silica can be found on Earth in obsidian rocks and tektites. Obsidian
is black, shiny volcanic glass. Tektites are hardened chunks of lava
that are thought to form when meteorites hit the Earth. Large
quantities of silicon monoxide gas were also detected, presumed to
have been created when a lot of the rock was vaporized. In addition,
the astronomers considered that the information from Spitzer included
evidence of rocky rubble, The mass estimated for the material and gas
observed suggests that the combined mass of the two colliding bodies
was more than twice that of our Moon. The two bodies would have been
travelling at a relative velocity of at least 10 km/s before the
collision.


IN SEARCH OF ANTIMATTER GALAXIES
NASA

With only about half a dozen more Shuttle flights to come, crews will
add further units to the International Space Station, bringing to an
end twelve years' US contributions to the orbital construction. A
flight near the end of the programme in 2010 will deliver the 'Alpha
Magnetic Spectrometer' (AMS) cosmic-ray detector that will hunt for
anti-matter galaxies. In addition to sensing distant galaxies made
entirely of anti-matter (if such a thing were to exist), the AMS will
test theories of dark matter and search for 'strangelets', a highly
speculative form of matter. Some understanding of strangelets might
help scientists to study micro-quasars and tiny, primordial blacks
holes as they evaporate, thus proving whether such small black holes
even exist. All such exotic phenomena might make their presence known
by the ultra-high-energy cosmic rays that they might emit -- the type
of particles AMS is intended to detect.

According to physicists' models, the Big Bang ought to have produced
just as much antimatter as matter -- but we do not see any. It can't
be nearby, because if it were, we would see bright X-ray emissions
where the antimatter came into contact with matter and annihilated.
One, albeit far-fetched, explanation could be that some distant
galaxies are made entirely of antimatter instead of matter. Since
antimatter wouldn't look any different from ordinary matter,
astronomers would not be able to tell whether a distant galaxy were
made of matter or antimatter just by looking at it. However, AMS
would produce evidence of antimatter galaxies if it detected even a
single nucleus of anti-helium or a heavier antimatter element.
Collisions among cosmic rays near the Earth can produce antimatter
particles, but the odds against such collisions producing an intact
anti-helium nucleus are so vast that finding even one such nucleus
would strongly suggest that it must have come from a distant region
of the Universe dominated by antimatter -- truly a case of one swallow
implying a whole summer!

Other instruments such as the Italian PAMELA satellite have looked for
anti-helium nuclei, but none has been sensitive enough to rule out the
existence of antimatter galaxies. AMS has about 200 times the
particle-collecting power of anything that has flown before. If AMS
detects no anti-helium nuclei, even the diehards will have to accept
that there are no antimatter galaxies within about 1000 megaparsecs --
roughly to the edge of the observable Universe.


Bulletin compiled by Clive Down

(c) 2009 the Society for Popular Astronomy