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Comet watchers in the southern hemisphere are enjoying an unexpected but delightful treat. Comet 252P LINEAR, which was discovered in April 2000 by the LINEAR survey, wasn't expected to do or be anything special, and was supposed to be little more than a 12th magnitude smudge in large telescopes by now, but it has suddenly brightened to the point where even single unguided exposures are recording it, and some reports suggest it is even visible to the naked eye from a dark sky site. That would make it an incredible 9 magnitudes brighter than predicted.
Of course, by being expected to do one thing and then doing something completely different, 252P is following in the long and proud tradition of comets. That famous quote about comets being like cats - in that they have tails and do exactly what they want - certainly seems appropriate for 252P...
And it's big too. Photographs show its coma is almost twice as wide as the Moon, although it doesn't look that big to the naked eye, not with the growing Moon nearby.
Southern hemisphere observers have really been enjoying the comet's apparition though. Recently 252P presented an unmissable photo opportunity when it drifted past the Large Magellanic Cloud, and understandably many astrophotographers relished the opportunity to capture both objects in one picture. For example, this 2 minute single exposure image by Australian astrophotographer Alex Cherney, taken from Flinder Victoria at 2am on march 16th, shows a beautiful contrast between the glittering silvery blue stars of the Magellanic Cloud and the comet's striking green glow...
252P is heading north, but it will not be visible in the northern sky until the very end of March, when it will poke its head over the eastern horizon before dawn, sailing up towards but to the left of Saturn and Mars.
Unfortunately we won't have anywhere near as good a view of it then as our friends in the south have had; when it reaches our skies it will be moving into a sky lit not just by the approach of dawn but by a big Moon too. In fact the comet will appear very close to the Moon on the morning of March 30th. Still, even thoigh it will be diffuse and faint, 252P will be well worth looking for, with binoculars and telescopes, and when the Moon eventually moves out of the way in early April 252P will be higher, and in a darker sky, and should be a good photographic target, especially for people with equipment that can track the sky as it moves. And, fingers crossed, shouldn't be too hard to see in small telescopes and binoculars too. The charts, below will help you find it.
252P isn't just noteworthy because of its sudden brightening. It is going to pass very close to the Earth in a couple of days, but nowhere near close enough to be a risk, despite what you will no doubt read in certain newspapers and online. In fact, when it whizzes past us on March 21st, at its closest 252P will still be fourteen times farther away than the Moon. A day later another comet - P/2016 BA14 PANSTARRS - will pass us at an even closer distance, but it will still come no nearer than nine times the distance to the Moon, so nothing to worry about there either.
Added by: Stuart Atkinson