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A comet meets
a globular cluster

Posted: 02 February 2012

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Comet Garradd has a spectacular conjunction with a bright globular cluster in the early hours of the next two mornings (2/3 and 3/4 February) when it passes around half a degree from M92 (NGC 6341). This will be a fine observing and imaging opportunity and for once the weather forecast looks reasonable across the majority of the UK.

Comet Garradd passes close to M92 in Hercules over the next few nights. AN graphic by Greg Smye-Rumsby.

Comet Garradd (2009 P1) has been a feature in the night sky for a number of months now and has been resident in the constellation Hercules since late September. It has been steadily brightening as it closed in on the Sun, reaching perihelion in late December and it is now holding steady at around magnitude +7, unfortunately beyond naked eye range but an easy binocular and telescopic object. M92 (R.A. 17h 17m 07.3s, Decl. +43° 08’ 11”) is one of the finest globular clusters in the Northern Sky, shining at mag. +6.5 and spanning 14 arcminutes in size. It too will be an easy binocular object but will require apertures in excess of 100-mm to resolve individual stars.

Garradd is now circumpolar from the UK (always above the horizon, as is M92) but observers will have to wait until around 1am for the pair to attain a decent altitude of 20 degrees or so above the north-eastern horizon. It will be well worth the wait as recent images show the comet to be a spectacular object, exhibiting a bright nucleus roughly similar in size to M92, fan-shaped dust tail and a thin gas tail pointing almost directly away from the Sun. A waxing gibbous Moon is still up over in the west but sets around 5am on 3 Feb and 5.40am the next night.

The comet remains within five degrees of M92 until the 8/9 February as it continues to track north, moving into Draco in mid February, skirting Ursa Minor in early March whilst approaching closest to the Earth and then peaking in declination on 11 March at +71°. It remains circumpolar to the end of April when, hopefully it will still be an eight-magnitude object in Lynx.