*********************************** 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 The Society for Popular Astronomy has been helping beginners to amateur astronomy -- and more experienced observers -- for more than 50 years. If you are not a member then you may be missing something. Membership rates are extremely reasonable, starting at just £16 a year in the UK. 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