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The 31st International Meteor Conference (IMC) took place on La Palma in the Canary Islands between Thursday Sept 20 and Sunday Sept 23 2012. The 110 attendees were a mix of professional and amateur astronomers, plus a number of journalists invited by the La Palma authorities as part of their plans to promote astro-tourism on the island. Although most attendees were from European countries, some also attended from as far afield as Canada, the USA and Japan.
The Saturday afternoon included an excursion to the Observatorio del Roque de los Muchachos (altitude over 2400 metres) to see some of the telescopes, including the MAGIC telescopes, the William Herschel Telescope, the 10.4 metre Gran Telescopio Canarias and the (much smaller!) CILBO meteor camera. The observatory was reached via a long winding road which ran alongside alongside steep drops which were (only sometimes) “shielded” by crash barriers - La Palma is the "steepest" inhabited island in the world. Photos from this excursion can be found at www.popastro.com/meteor/reports/report.php
The meeting itself was held in the resort of Los Concajos on the east coast of the island. As at recent IMCs, most speakers were restricted to only 15 minutes so as to allow as many speakers as possible. Here is a summary of some of the presentations:
Sirko Molau (Germany) gave an overview of the 2011 results from a network of 80 cameras in 16 different countries, which has recorded over 300000 meteors. Attempts are being made to go beyond merely identifying meteor showers and meteoroid orbits and moving on to automatically determining limiting magnitudes and effective atmospheric collection areas. He also outlined the problems involved in correcting for radiant altitudes in ZHR calculations - the more “simple” formulas can often lead to spurious peaks in analyses. He showed how adjusting the formula can give better correction for low radiant altitudes.
Filip Novoselnik and Denis Vida (Croatia) described the possible detection of a new meteor shower in Croatian Meteor Network and SonataCo data. The shower may be an extension of the southern Delta Aquarids.
Felix Bettonvil (Netherlands) outlined early work involved in setting up an automated all sky camera system and highlighted the need to keep out dust and to control the humidity. Noise levels become high when the temperature increases – the internal temperature has on occasions reached 47C
Pete Gural (USA) gave an update on the CAMS system. This is funded by NASA and is based on having lots of cameras at a small number of stations and can record meteors down to mag +4. This has allowed 47000 meteoroid orbits to be defined in one year, with 31 new meteor showers being added to the IAU database. Future plans included capturing spectra of bright meteors. For more information, see http://cams.seti.org
Johan Kero (Sweden) described work carried out to detect meteor head echoes using the MU radar. Despite issues from operating in an auroral zone, this recorded 106139 meteors during 2009-10, with the highest velocities being, as expected, from meteors radiating from the apex direction. Future work will involve the EISCAT_3D system - see www.eiscat3d.se
Herve Lamy (Belgium) gave an update on the BRAMS network. This currently has 23 observing stations and uses its own radio beacon. Attempts are made to identify meteors seen from more than one station in order to determine trajectories – although this proved difficult during the 2011 Draconid outburst. For more info, see http://brams.aeronomy.be
Sylvain Ranvier (Belgium) described work carried out during the 2012 Perseids to measure radio polarisation. 158 echoes were detected, most of which were strongly polarised. The work has the potential to give insight into the physical phenomena that produce meteor echoes and into (epsilon) multiple branch echoes.
Jean-Louis Rault (France) gave an update on issues affecting radio meteor observations. The switchover of TV stations from analogue to digital is an increasing issue. Groups can set up their own beacons, but these will be low power and so observers have to be within a few hundred kilometres of the beacon. Other potential options include radar systems being set up by ESA and NORAD and also aviation radars.
Megan Argo (UK) gave a short talk about the work of Sir Bernard Lovell who died recently. She described how he had expected his early investigations at Jodrell Bank to reveal cosmic rays to be the cause of certain radar echoes, but instead found that ionised meteor trails were responsible. The 1946 Draconid storm was subsequently monitored at radio wavelengths. The presentation concluded with a short video in which Lovell described this early work.
Jiri Borovicka (Czech Rep) outlined the results of a 2011 expedition to northern Italy which succeeded in recording the spectra of 8 Draconids. These showed the meteoroids to have normal cosmic ratios for Mg, Na and Fe, to have a 90% porosity and were consistent with grains having a typical size of 50-120 microns
Damir Segon (Croatia) reported the results of the Croatian Meteor Network for the 2011 Draconids. Orbits were determined for 88 Draconids (25 being detected from 3 or more stations). However, the calculated aphelion distance for the orbits was very dependent on the deceleration model used, ranging from 4.9au to 6.0au
Stijn Calders (Belgium) described software that can be used to predict where in the sky a specular radio reflection was likely to occur for a particular meteor shower radiant location. This location inevitably moves as the radiant crosses the sky and can correspond to an area over 100km across.
Galina Ryabova (Russia) reviewed the possibility of the Earth encountering meteoroids ejected when 3200 Phaethon (the Geminid parent) brightened by over 2 magnitudes for 2 days in June 2009. The best chance will be when Phaethon approaches to 0.0689au of the Earth in 2017. The conclusion was that activity is possible, but the probability is not high.
Regina Rudawska (France) outlined the possibility of seeing meteors from asteroid 2012FZ23, an Apollo asteroid with a high inclination. The possible radiant would lie in the southern constellation of Chamaeleon.
Maria Hajdukova (Slovakia) reviewed the data for hyperbolic meteoroids. These have sometimes been suggested to be interstellar in origin. Alternatively, the hyperbolic classification might be the result of measurement errors or the meteoroids might only have become hyperbolic as a result of interactions within the solar system. The results of her investigations suggest that only 2-4% of “hyperbolic” meteors are really interstellar in origin.
Nagatoshi Nogami (Japan) gave an overview of the 50 meteorites that are known to have fallen in Japan. The oldest, the Noogata meteorite, dates from 861 May 9 and was for a long time stored in a shrine. Another, the Shirahagi meteorite was found in 1890 (date of fall unknown) and was for many years used for weighing a pickles cask. Later, part of it was used to make a 60cm sword. More recently, on 1992 Dec 20, the Mihogaseki meteorite broke a house roof and passed through two of its floors.
Damir Segon (Croatia) described work to detect meteors in the near infrared. The camera used had 60-70% sensitivity to the 777nm oxygen line and used a filter to cut out visual wavelengths. Some of the meteors detected show similar light curves in the visual and infrared whereas others are very different.
Thomas Weiland (Austria) gave an overview of work to monitor the Eta Aquarids from La Palma in 2011. Over 7 nights, during which the LM ranged from 6.3 to 6.9, two observers recorded 354 Eta Aquarids, including two Earth grazers, but few fireballs were seen. The peak ZHR was around 55 during May 6-7.
Geert Barentsen (UK) reviewed the issue of how to determine the flux of large meteoroids. The US Military have data which indicate 300 large bolides were detected during 1994-2002, but this data is restricted. He suggested that monitoring Twitter for bursts of tweets mentioning words such as “fireball” or “meteor” can give an indication as to when major fireballs are seen (the Sep 21 UK fireball which had appeared the previous evening produced one such burst of tweets).
Guliyev Ayyub (Azerbaijan) summarised the various groups of sun-grazing comets and reviewed the likely meteor streams that may be associated with these. Unfortunately none of these seem to currently pass close to the Earth.
Danielle Roser (USA) described the results of attempts to simultaneously observe the 2012 Lyrids from three different locations: from the ISS by astronaut Don Pettit (altitude around 400km), from a balloon (altitude 35km) and from the ground. 155 meteors (16 double station) were seen from the ground, but only 2 of these were possible recorded from the ISS. The balloon’s useful recording time was 1.6 hours during which 31 meteors were recorded, but none of these were recorded by the other two methods.
Ovidiu Vaduvescu (Romania) described the EuroNEAR collaboration. In the absence of a dedicated European telescope for NEA detection, this involves scanning plate archives for possible images in order to find pre-discovery images.
The 2013 International Meteor Conference is due to take place in Poznan, Poland from Thursday August 22 to Sunday August 25.
Added by: Tracie Heywood