The Coma Berenices Star Cluster, Melotte 111
Open Cluster Melotte 111
Right Ascension | 12 : 25: (h:m) |
---|---|
Declination | +26 : (deg:m) |
Distance | 0.288 (kly) |
Visual Brightness | 1.8 (mag) |
Apparent Dimension | 275 (arc min) |
This large and conspicuous cluster was first cataloged by Ptolemy; it is scattered
over an area of about 4.5 degrees diameter. Although conspicuous, it was neither
included in Messier’s nor in the NGC catalog, because its nature as a true,
physical cluster was proven only by R.J. Trumpler who identified 37 stars as true
cluster members.
The Coma star cluster is currently neither approaching nor receding from us, i.e.
it moves tangentially to us with a velocity directed to position angle PA=218 deg,
visible as a proper motion of 0.02 arc seconds per year. So member stars are
easily identified by having this proper motion and no Doppler shift in their
spectra. Its distance has recently been refined by data of ESA’s astrometric
satellite Hipparcos, and is now estimated at 288 light years (previous estimate
was 260).
The Sky Catalog 2000 gives an age of 400 million years, and the brightest star as
of apparent magnitude 4.35, the hottest spectral type of A0.
Our image was obtained by amateur
More images from Jack Schmidling
In John Caldwell’s observing list.
Last Modification: 25 May 1999, 16:35 MET