Comet 252P/LINEAR Brightening Much Faster than Expected

On March 21st, Comet 252P/LINEAR will make a close approach to Earth–only 0.036 AU (5.4 million km) away. This is the fifth closest cometary approach on record and, as a result, the normally dim comet could become an easy target for backyard telescopes. In fact, it is brightening much faster than expected: data. “Comet 252P/LINEAR has surpassed expectations and is now bordering on naked eye visibility for southern observers,” reports Michael Mattiazzo of Swan Hill, Victoria, Australia, who took this picture on March 13th:

Comet 252P LINEAR has surpassed expectations by showing a remarkable rate of brightening, about 0.5 magnitudes per day, over the period May 7 to 14 and is now bordering on naked eye visibility for southern observers.

The very large, diffuse coma is expanding rapidly, from 10 arcminutes on March 7 to 35 arcminutes on March 14. It may reach 1 degree across at closest approach on March 21. A dark southern sky and a good pair of binoculars is essential.

“Since March 7th, the comet has brightened about 0.5 magnitudes per day,” continues Mattiazzo, “and now it is near 6th magnitude. The comet’s atmosphere (coma) is expanding rapidly, too, from 10 arcminutes on March 7th to 35 arcminutes on March 14th. It may reach 1o across by March 21st.”

This is a southern hemisphere event. At closest approach on March 21st, the brightening comet will speed through the constellations Triangulum Australis and Apus. Observers south of the equator can use this ephemeris to point their telescopes. In remote places with very dark skies, it is possible that no telescope will be required; naked eyes might suffice. Stay tuned for updates as the comet approaches.