Tuesday, March 18, 2008

State of the art of meteor astronomy evident at German conference

As every year the - already 27th - AKM-Seminar, this time in Freital near Dresden, gave a great overview about the state of the art of meteor observation and analysis: This is one of the fields of astronomy where the level of amateur work is not much different anymore from what the (few) professionals in the field do.
  • This is particularly evident in the IMO Video Meteor Network to which now 20+ cameras contribute (15+ of them every clear night) and which netted 75,070 meteors in 2007 - the annual yield has been climbing linearly for years now. The 330,000 meteors in the data base will be analyzed for known and unknown meteor streams again this summer by sophisticated (and extremely CPU-intensive!) software: While visual observations still form the traditional base of our knowledge of meteoroid clouds moving through the solar system and being intercepted by Earth, the never-tiring video cameras add more and more insights. And mysteries: This March 6 and 9, the two meteors were recorded travelling in close proximity at the same time, something never seen before in 100,000s of cases ...

  • While meteor stream modelling has greatly advanced in the past ten years, thanks to the Leonid storms, there are still surprises happening (so one should be observing at every opportunity): For example in 2006 and again in 2007 the Orionids were more active than usual, with Zenithal Hourly Rates in the 60s instead of 20-25. This has since been explained by a 6:1 resonance with Jupiter of the meteoroids which not only explains enhanced Orionid activity in 1936, 2006 and 2007 but also predicts high rates of these bright meteors in 2008 as well as 2009 and 2010. Unfortunately the 2008 Orionids will suffer from moonlight as will the Geminids: The Perseids - with an expected ZHR of 110 - will be the only major shower this year free of lunar interference.

  • When major fireballs light up the sky anywhere over Europe Thomas Grau will travel there, interview eye (and ear!) witnesses and go on a hunt for meteorites if a strewnfield is deemed likely and its location has been calculated. The results from extensive witness 'interrogation' can at times be more precise than using imagery from fireball camera networks, says Grau, who reported on three recent cases.

    • The famous 1 March 2008 fireball had at first been suspected to have dropped small meteorites near (or even into) Lake Constance - simply because many early eyewitness reports had come from that area. But further reports have now made it clear that any meteorites would have fallen in central Switzerland instead where going after them will be tough. The characteristics of the fireball could also mean, though, that no solid matter reached the ground at all.

    • Similarly confusing were the first reports about a fireball in France on 25 January 2008, 15 minutes after sunset. A cloud in the sky remained and was photographed, but because of wind drift its use for determining the trajectory was limited. Fireball sighting vectors from reliable witnesses, however, meet near one location, in the vicinity of Montpellier - and several mentioned strange "red and blue flames" trailing the fireball. No meteorites yet either.

    • The last major success happened in Spain after a daylight fireball on 10 May 2007 which was accompanied by loud noises and shaking ground like during an earthquake. Although only 5 really good witnesses could be located, from their sightings and acoustical recollections a search zone could be located - and soon five small meteorites were found (among tons of meteowrongs in olive plantations). A further search by Grau yielded 10 more, and overall 100+ meteorites have been found in a 7 x 3 km zone, with together 800 grams - and they are eucrites, i.e. most likely splinters of asteroid Vesta.
Apart from meteors (and meteorite hunts and investigations of impact craters - real ones, not this one) the Arbeitskreis Meteore also deals with atmospherical optics of the traditional and also very non-traditional kind. Classical halo phenomena by ice crystals (in the atmosphere or elsewhere) are nowadays accompanied by optical effects of all kinds, be it in bacteria slime layers on ponds or in cat hairs. Some AKM members also love to do experiments, and it order to demonstrate his insights into rainbow physics C. Fenn actually performed a spectacular show for the conference crowd - with a rotating laser beam and water spray in a nightly parking lot ...

In other news the Moon and Saturn will meet tomorrow, a Saturn animation clearly shows its elusive rotation pattern, and even with 8" but modern electronic cameras amazing Saturn images are possible today.

Another impact on the Moon has been videographed, this time from Maryland, astonishing lunar images with cell phone cameras, just held behind a telescope eyepiece, are possible - and you can bring out color on the Moon (that normally just looks yellowish) with clever image processing!

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