Melotte 20 (Collinder 39, the Alpha Persei Moving Cluster)
Constellation: Per
Object Type: Open Cluster
RA: 3h 21m 31s
Dec: +48° 34' 45"
Magnitude: 1.2
Recommended minimum aperture: 50mm
Charts for 50mm Binocular (5° aperture circle). Click on a chart to print it.
Location:
Mel 20 is the cluster of stars, many of which are visible to the naked eye, around ? Persei (Mirfak).
What You Should See:
These stars are mostly very bluish (spectral types O and B), indicating their relative youth (a few tens of millions of years). This is an ideal object for small and medium binoculars, which are able to encompass most or all of the cluster in their field of view. You should easily be able to see more than fifty stars, lying 557 to 650 light years away. It is only about 60 million years old and is called “moving” because all the stars share a similar proper motion (motion relative to the celestial sphere) of around 33 milliarcseconds per year.
