RAS: The shocking size of Comet McNaught

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bystander
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RAS: The shocking size of Comet McNaught

Post by bystander » Tue Apr 13, 2010 1:05 am

The shocking size of Comet McNaught
Royal Astronomical Society Press Release
RAS PN 10/24 (NAM 08) 13-Apr-2010
British scientists have identified a new candidate for the biggest comet measured to date. Dr Geraint Jones of UCL’s Mullard Space Science Laboratory will be presenting the results at the RAS National Astronomy Meeting in Glasgow on Tuesday 13th April. Instead of using the length of the tail to measure the scale of the comet, the group have used data from the ESA/NASA Ulysses spacecraft to gauge the size of the region of space disturbed by the comet’s presence. Analysis of magnetometer data shows evidence of a decayed shockwave surrounding the comet created when ionized gas emitted from the comet’s nucleus joins the fast-flowing particles of the solar wind, causing the wind to slow down abruptly.

In January and February 2007, Comet C/2006 P1 McNaught became the brightest comet visible from Earth for 40 years. Serendipitously, Ulysses made an unexpected crossing of Comet McNaught’s tail during this time, one of three unplanned encounters with comet tails during the 19-year mission. The other encounters included Comet Hyakutake in 1996, the current record-holder for the comet with the longest measured tail.
Stunning Comet's Size Shocks Scientists
Space.com 12 Apr 2010
Comet McNaught, the so-called Great Comet of 2007, has been identified as the biggest comet measured to date, according to scientists, whose calculations were based on the comet's overall influence in space.

Instead of using the length of the comet's tail to measure the scale of the comet, astronomers used data from the ESA/NASA Ulysses spacecraft to determine the size of the region of space disturbed by the comet's presence – a cosmic wake across the solar system.

Through analysis of magnetometer data, scientists found evidence of a decayed shockwave surrounding the comet, which was created when ionized gas emitted from the comet's nucleus joined the fast-flowing particles of the solar wind. That, in turn, caused the solar wind around the comet to abruptly slow down.
Image
Comet McNaught over the Pacific Ocean. Image taken from Paranal Observatory in January 2007. (S. Deiries/ESO)