- Girvan McKay, Midlands Astronomy Club
- Eamon Ansbro, Kingsland Observatory, Roscommon
- Kevin Berwick, Dublin
- Dermot Gannon, Midlands Astronomy Club
- Apostolos Christou, Armagh Observatory
- Lawrence Rigney, Midlands Astronomy Club
More details are available on the website www.midlandsastronomy.com
8. JUPITER HELPS HALLEY'S COMET GIVE US MORE SPECTACULAR METEOR DISPLAYS. The dramatic appearance of Halley's comet in the night sky has been observed and recorded by astronomers since 240 BC. Now a study shows that the orbital influences of Jupiter on the comet and the debris it leaves in its wake are responsible for periodic outbursts of activity in the Orionid meteor showers, according to a paper presented by Aswin Sekhar of Armagh Observatory, at the National Astronomy Meeting in Manchester on Tuesday 27th March.
Halley's comet orbits the Sun every 75-76 years on average. As its nucleus approaches the Sun, it heats up and releases gas and dust that form the spectacular tail. This outgassing leaves a trail of debris around the orbit. When the Earth crosses Halley's path – twice per orbit – the dust particles burn up in the Earth's atmosphere and we see meteor showers: the Orionids in October and the Eta Aquariids in May. Previous research has suggested that Orionid meteoroids have at times fallen into 'resonances' with Jupiter's orbit – a numerical relationship that influences orbital behaviour. Sekhar's new study suggests that Halley itself has been in resonances with Jupiter in the past, which in turn would increase the chances of populating resonant meteoroids in the stream. The particles ejected during those times experience a tendency to clump together due to periodic effects from Jupiter.
"This resonant behaviour of meteoroids means that Halley's debris is not uniformly distributed along its orbital path. When the Earth encounters one of these clumps, it experiences a much more spectacular meteor shower than usual," said Sekhar. Sekhar's work suggests that the unusual Orionid outburst observed in 1993 was due to 2:13 resonant meteoroids ejected from Halley around 240 BC.
9. TWITTER: the IAA now has a twitter account. twitter@IaaAstro