M47
NGC 2422
Properties
Position & Identifiers
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M47 · 19.8′ diameter · N up, E left
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About M47
Description
M47 is a bright, coarse open cluster in Puppis, about 1,600 light-years from Earth. It contains roughly 50 stars spread across about 12 light-years, with an age of 78 million years. The cluster's brightest members are blue-white B-type stars, and it includes several attractive double stars.
Observing Tips
Located about 1 degree west of M46. Visible to the naked eye as a hazy patch about the size of the full Moon. Binoculars show a bright scattering of about 20 stars. A telescope at low power (30-50x) provides the best view, revealing bright stars with nice color contrasts. The pairing with M46 in a wide-field view is one of the finest double-cluster sights in the sky. Best observed from January through April.
History
Known since antiquity — likely the object recorded by Giovanni Battista Hodierna before 1654. Charles Messier cataloged it in 1771, but with an error in position that caused it to be 'lost' for over a century until identified with NGC 2422 by Oswald Thomas in 1934.
Fun Facts
M47 was a 'lost' Messier object for over 160 years due to a sign error in Messier's coordinates. The error made the recorded position point to empty sky. Canadian astronomer T.F. Morris confirmed its identity in 1959. M47 and M46 together make a superb visual pair, demonstrating the difference between a nearby bright cluster and a distant rich one.