M47 (ngc2422)

M47 (ngc2422) is an open cluster of stars in the constellation of Puppis. It was discovered by Giovanni Batista Hodierna before 1654 and independently rediscovered by Charles Messier in 1771. Because of a confusion in Messier's report on the cluster with regards to its position, the cluster was considered "lost" and it wasn't until 1959 that the Canadian astronomer, T.F. Morris, realised that the object designated ngc2422 and M47 were one and the same.

M47 lies 498pc-1623.48 l.y. in distance and is 21.22 l.y. in diameter. The cluster's 500 or so members weigh in at around 453 solar masses, making the average star in the cluster around 90% of the Sun's mass (G class, at least). The largest and brightest of the cluster's stars is HD60855, 5.7mag Be star. Though the cluster is dominated by bright B class main sequence stars and giants, there are a number of red giants in the cluster. Meaning it's most massive stars have already evolved away from the Main Sequence. The MS turnoff point of the cluster gives it an age of around 78million years. Which gives a turnoff mass of about 7 solar masses and a spectral class of around B1-2. As the cluster ages, the turnoff point will slowly move down the MS to later spectral classes. However, by the time it goes too much further the cluster will have broken up and dissolved into the general field of stars within the Galaxy. The average stars of the cluster (in mass) will be on the MS, but it's smallest stars, lowest K and M class stars, will still be contracting to the MS.

Notably, M47 lies about a degree away from another star cluster, M46 (not in the FoV). However, they are not associated and M46 is considerably further away and much older.

Pic was taken with t68 at the Bathurst Observatory (BAT-iTelescope Network). 15x60sec subs.
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