M 52

M52 is a fine open cluster located in a rich Milky Way field. It is one of the rich clusters for which amateur Jeff Bondono has proposed the name "salt and pepper" clusters. Ake Wallenquist (1959) found 193 probable members in a region of 9' radius, and the density near the center is about 3 stars per cubic parsec.

The brightest main sequence star of this cluster is of mag 11.0 and spectral type B7. Two yellow giants are brighter: The brightest is of spectral type F9 and mag 7.77, the other of type G8 and mag 8.22. The Sky Catalog 2000 gives an age of only 35 million years, which the present author estimates as too low.

The distance of this cluster is not very well known; Kenneth Glyn Jones adopts 3,000 light years, while the Sky Catalog 2000 gives 5,200 (i.e., 1,600 pc). This uncertainty is mainly due to the high interstellar absorption its light has suffered on its way to us, which is complicated to estimate reasonably.

Right ascension	23 : 22.0 (hours : minutes)
Declination	+61 : 20 (degrees : minutes)
Distance	7.0 (light-years*10^3)
Visual magnitude	7.3