On the afternoon of 21 March, Comet 252P/LINEAR brushed by Earth just 14 lunar distances away. In the intervening 5½ weeks the comet’s rapid ascent into northern skies has slowed owing to its increasing separation from our planet and as its motion describes a graceful clockwise loop through northern Ophiuchus. On 10 May, 252P reaches a peak northerly declination of +9.1 degrees whereupon it starts to head south, still following an almost circular arc, crossing the constellation border into Hercules on 26 May.
Now that this fascinating comet is visible from the UK low in the east before midnight, make the most of any clear skies you may have over the coming week to view 252P/LINEAR in a moonless sky before it fades below the range of binoculars and small telescopes. A periodic comet with a 5⅓-year orbit, 252P is currently about a quarter of an astronomical unit (~23 million miles) from Earth, but it can still be seen as a diffuse circular glow with minimal optical aid if you can find an observing location that is devoid of streetlights and other sources of artificial illumination.In the telescope, 252P presents a diffuse round coma about two-thirds of a degree across (somewhat larger than the full Moon in angular size) with virtually no tail. It’s still relatively bright, with an integrated magnitude of around +6.5, but fading. Astroimagers will readily capture its greenish-blue colour due to diatomic carbon (C2) molecules fluorescing in the sunlight.
Inside the magazine
Find out all you need to know about observing Comet 252P/LINEAR and the other solar system bodies currently in the night sky in the May 2016 edition of Astronomy Now.
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