Alpha Persei Cluster

Alpha Persei Cluster
Observation data (2000.0 epoch)
Constellation	Perseus
Right ascension	03h 26.9m
Declination	+49° 07′
Distance	557-650 ly[1][2][3] (171-200 pc)
Apparent magnitude (V)	1.2
Apparent dimensions (V)	185'
Physical characteristics
Other designations	Cr 39, Mel 20
See also: Open cluster, List of open clusters

The Alpha Persei Cluster, also known as Melotte 20 or Collinder 39, is an open cluster in the constellation of Perseus. To the naked eye, the cluster consists of several blue spectral type B type stars. The most luminous member is the ~2nd magnitude white-yellow supergiant Mirfak, also known as Alpha Persei. Bright members also include Delta, Epsilon, Psi, 29, 30, 34 and 48 Persei. The Hipparcos satellite and infrared color-magnitude diagram fitting have been used to establish a distance to the cluster of ~172 pc.^[2][3] The distance established via the independent analyses agree, thereby making the cluster an important rung on the cosmic distance ladder. The age of this cluster is about 50-70 million years.^[1][4]

Members

Designations	Spectral type & Luminosity class	Comments
α Per (33 Per)	F5Ib
δ Per (39 Per)	B5III
ε Per (45 Per)	B1V
ψ Per
29 Per
30 Per
34 Per
48 Per

References

1. ^ ^{a b} Prosser, Charles F.; Randich, Sofia; Stauffer, Joh R.; Schmitt, J. H. M. M.; Simon, Theodore (October 1996). "ROSAT Pointed Observations of the Alpha Persei Cluster". Astronomical Journal 112: 1570. Bibcode 1996AJ....112.1570P. doi:10.1086/118124. 
2. ^ ^{a b} van Leeuwen, F. "Parallaxes and proper motions for 20 open clusters as based on the new Hipparcos catalogue", A&A, 2009
3. ^ ^{a b} Majaess, D.; Turner, D.; Lane, D.; Krajci, T. "Deep Infrared ZAMS Fits to Benchmark Open Clusters Hosting delta Scuti Stars", JAAVSO, 2011
4. ^ Paunzen, E., Mermilliod, J.-C. "WEBDA: Alpha Persei"

External links

• Alpha Persei Moving Cluster, Mel 20
• The Alpha Persei Cluster (Mel 20)
• Spectral types in the Alpha Persei Cluster

Coordinates: 03^h 22^m 00^s, +49° 00′ 00″