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Is Comet Siding Spring splitting up?
Posted: 17 March 2010, updated 18 March

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This dramatic image, captured by Astronomy Now's Nick Howes of Comet C2007 Q3 Siding Spring on Wednesday, suggests that the comet's nucleus might be disintegrating.

Comet C2007 Q3 Siding Spring as imaged by Nick Howes using the Faulkes Telescope North on 17 March at 15:00 UT. Image details: 6 x 60s images in R,G,B filters processed in Maxim DL (DDP). The comet was positioned at RA 15 22.76 and dec +56 12.4.

Using the Faulkes Telescope North, Nick imaged the magnitude ten comet in glorious detail, identifying a possible split in the comet's nucleus, seen in the image as a second site of denser material just behind the main nucleus.

Nick is making more observations on Friday, but tells us, "I have confirmed via creating an animation that the secondary condensation is moving WITH the comet and is not a background star."

Nick's animation of Comet Siding Spring.

Could this represent the onset of an outburst event? In just the last few days, comet C/2009 O2 (Catalina), has been reported by various observers as breaking up, and two years ago Comet 17P/Holmes displayed a spectacular outburst event that was so violent it blew huge chunks of the comet's surface clean off as it became heated up by the Sun on its elliptical journey through our Solar System. Each fragment was like a mini-comet, with its own coma of dust as ice vaporised from their surfaces.

Nick's image of Comet C2007 Q3 Siding Spring taken from his back garden in Wiltshire on 15th and 16th March 2010, at approx 00:00 to 01:00 UT, imaged with an Atik 314L camera on a TMB 105 telescope.

Looking at his own images Nick comments "At the time I didn't think much of the change in tail size, but this could be related." Nick adds that an amateur with a large telescope should be able to do follow on observations of this event. Ephemerides for the comet can be found on the British Astronomical Association's Comet section webpage and you can send any reports to the BAA, and of course to us at web2010(at)!

Last year astronomers Sostero, Guido and Camilleri flagged up an unusual appearance in Comet Siding Spring, commenting on "the presence of an asymmetric coma, with a possible feature exiting toward East, North-East, developing in a counterclockwise direction." At the time this was attributed to a foreshortening effect, and in their most recent image of the comet, taken on 13 March 2010, the feature seen in Nick's image is not present.

Sostero and Guido's image of Comet Siding Spring on 13 March does not reveal the splitting event.

Comet C2007 Q3 Siding Spring was discovered by Donna Burton in 2007 at the Siding Spring Observatory in New South Wales, Australia. It reached perihelion in mid-October, passing within 1.2 astronomical units of the Earth, and was visible with binoculars until the start of 2010, when it tracked through the constellation Bootes.

Read more about Comet Holmes' outburst in our reports here:
25 Oct 2007 Comet brightens a million times
15 Oct 2008 Spitzer peers inside Comet Holmes
16 Sept 2009 Comet Holmes produced mini-comets