Goodbye to Comet Garradd
BY MARK ARMSTRONG
Posted: 17 May 2012
Alan C Tough got up at 4 a.m. on February 3, 2012 to capture Comet Garradd's close encounter with the beautiful globular cluster M92. Equipment used: Sky-Watcher ED100, HEQ5 mount, Canon EOS 60D at prime focus. Exposure details: 360 secs @ f/9, ISO-800. Guiding equipment: Sky-Watcher ED80, StarShoot Autoguider. Processed using Photoshop and Noel Carboni's Astronomy Actions. Image: Alan C Tough.
Comet 2009 P1 (Garradd) has been a very welcome icy visitor from the frozen, far-flung reaches of the Solar System but make sure you observe it soon as May is the last month it will be reasonably placed. Although it has not been a spectacular naked eye comet like Hale-Bopp or Hyakutake, it has provided long-suffering comet observers with a decent show for almost a year. Garradd is now heading back out of the Soar System and is already past the orbit of Mars.
The comet is presently tracking south through Cancer and is still a good target for large binoculars and small telescopes shining around magnitude +9 and estimates of the coma range from five to twelve arcminutes. As night falls around 10pm BST Garradd is about 45 degrees above the western horizon, with about a two hour observing window before it starts to be engulfed by the poor conditions closer to the horizon. The Moon is co-operating for a week or so as it wanes towards new on 21st May and waxes towards first quarter for a few days after new Moon. By the end of the month it starts to get dark around 10.30pm but the comet is only 27 degrees up then and there is only about an hour to observe it and also the gibbous Moon will interfere. Hopefully there will be some clear, transparent evenings to enjoy the comet as by mid June it will have faded by maybe a magnitude and effectively lost to the evening twilight.
Comet 2009 P1 (Garradd) is reaching the end of its period of visibility from the UK. Follow its progress through Cancer for the rest of May. Graphic made using Megastar version 5.
Comet Garradd was discovered by Gordon J Garradd in August 2009 from Siding Spring Observatory in Australia and this is likely its first visit to the Solar System from the Oort Cloud, a spherical cloud of comets lying around 50,000 Astronomical Units (AU) from the Sun. Unfortunately Garradd never came particularly close to the Sun, its average distance was never closer than that of Mars. Garradd reached perihelion (closest to the Sun) on 23 December 2011 at a distance of 1.55 A.U. Neither did it approach Earth that close; it passed around 190 million kilometres (1.27 A.U.) from Earth on 5 March. These factors stopped it becoming a great comet but it has been well observed and imaged as it passed close to a number of fine deep sky objects, including the globular cluster M15 in Pegasus in early August, globular M71 in Sagitta in late August, the Coathanger asterism in Vulpecula in September and most notably the great globular M92 in Hercules in February. Deep images around this time revealed a second bluish ion tail pointing away from the Sun along with the dust tail trailing away from the nucleus.
The comet was circumpolar from the UK from February to April, enabling observations in a dark sky and close to the zenith, a luxury not that often enjoyed as many comets can only be observed in twilight conditions closer to local horizons. So all in all, 2009 P1 (Garradd) has been a fine comet, much enjoyed by observers. There is still a bit of time to observe it so make most of it if you can.