Comet may deliver firework show

Posted on October 27th, 2010

A green comet that has been passing close to Earth this month, setting a challenging target for amateur astronomers, may be set to produce a meteor shower. All-sky cameras have caught two brilliant fireballs streaking through the sky over the US and Canada.

Comet Hartley 2 by Nick Howes from Cherhill, UK on October 22

Now NASA experts say we should watch out for early fireworks with a possible meteor shower predicted next Tuesday and Wednesday, November 2 and 3, by Peter Brown of the University of Western Ontario.

Comet Hartley 2 has been making one of the closest approaches to Earth by a comet in centuries. Just 11 million miles away, it was closest last Wednesday appearing as a large fuzzy glow through stargazers’ backyard telescopes.

Warmed by the sun, it revealed a green gaseous shell, including the deadly gas cyanide, and a tail of ejected dust – the material that burns up as meteors or shooting stars. The comet was discovered by UK-born professional astronomer Malcolm Hartley from Siding Spring, Australia.

NASA’s Deep Impact probe will fly past Comet Hartley 2 on Wednesday November 4 and is expected to send back dramatic photos of its rocky heart, or nucleus. The probe previously made a spectacular missile attack on another comet, Tempel 1, in 2005 and is also hunting new planets!

The prospect of a meteor shower was raised after NASA all-sky cameras recorded a fireball over Alabama and Georgia on October 16. It was logged as unusual because calculations showed it had a similar orbit to another fireball snapped over Canada five hours earlier by a camera operated by the University of Western Ontario.

The orbits of both fireballs were found to be roughly similar to that of the comet, suggesting they were chunks of it which once broke off its nucleus. Both entered the atmosphere at relatively low speeds just as would be expected from this comet.

Bill Cooke, of NASA’s Meteoroid Environment Office, said: “The orbits of the two fireballs were very similar. It’s as if they came from a common parent.” He stressed that this could be a coincidence because thousands of meteoroids hit Earth’s atmosphere every night.

But he added: “The comet has been sputtering space dust for thousands of years, making a cloud that is much bigger than the comet itself. Solar radiation pressure and planetary encounters cause the comet and the dust cloud to diverge — not a lot, but enough to make the date of the shower different from the date of the comet’s closest approach.”

If there is a shower, Cooke says they will appear to streak in from the constellation of Cygnus the Swan which will lie overhead after sunset in early November. The last comet that showed such a large ball of gas was Comet Holmes following its incredible flare-up in 2007.

Our picture of Comet Hartley 2 was taken by UK amateur astronomer Nick Howes on October 22 using a CCD camera attached to a 4-inch (105mm) telescope. He plans to work with an Italian team to image the comet while the spacecraft, also called Epoxi, is making its closest approach.

Nick told Skymania: “The Italian team I am working with are also monitoring (using my images) some recent outbursts of gas from the comet, which have caused brightening. This may, and I stress “may”, be indicative of more activity such as fragmentation, but this is not clear at this time. The analysis is still ongoing.

NASA also, using their spacecraft, detected anomalies in the comet, which tied up with the results we were seeing from the ground based telescopes.”

If you want to find Comet Hartley 2 while it is still visible in binoculars and small telescopes, check out the finder chart provided by the Society for Popular Astronomy, including recent photos and observations.

• Discover space for yourself and do fun science with a telescope. Here is Skymania’s advice on how to choose a telescope. We also have a guide to the different types of telescope available. Check out our monthly sky guide too!



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