Alpha Persei Cluster

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Alpha Persei Cluster
Melotte 20.jpg
Observation data (2000.0 epoch)
Right ascension 03h 26m 42.0s [1]
Declination +48° 48′ 00″ [1]
Distance 570  ly [1] (175  pc [1] )
Apparent magnitude  (V)1.2
Apparent dimensions (V)6.1° [1]
Physical characteristics
Estimated age49.5±6.0  Myr [2]
Other designationsPer OB3, [3] Cr 39, Mel 20, OCl 392.0 [4]
Associations
Constellation Perseus
See also: Open cluster, List of open clusters

The Alpha Persei Cluster, also known as Melotte 20 or Collinder 39, is an open cluster of stars in the northern constellation of Perseus. To the naked eye, the cluster consists of several blue-hued spectral type B stars. The most luminous member is the ~2nd magnitude yellow supergiant Mirfak, also known as Alpha Persei. Bright members also include Delta, Sigma, 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 ~560 light-years (172  pc ). [5] [6] The distance established via the independent analyses agree, thereby making the cluster an important rung on the cosmic distance ladder. As seen from the Earth, the extinction of the cluster due to interstellar dust is around 0.30. [7]

Contents

The cluster is centered to the northeast of Alpha Persei. [7] It has a core radius of 11.4 ± 1.4 ly, a half-mass radius of 18 ly, [7] and a tidal radius of 70.6 ± 8.5 ly, [1] with 517 members being identified within the latter. [7] The cluster shows solid evidence of having undergone mass segregation, with the mean stellar mass decreasing toward the edge. [8] The age of this cluster is about 50–70 million years. [9] [10] Cluster member stars show a near-solar metallicity, meaning the abundance of elements with atomic numbers higher than 2 are similar to those in the Sun. [7] The cluster shows evidence of tidal tails, which are most likely of galactic origin. [11]

The cluster field displays evidence of a much larger, background star stream. This feature is quite a bit older than the cluster, with an estimated age of 5 ± 1 Gyr. The center of the stream lies 290 ly from the cluster and it has an overall thickness of 590 ly along the line of sight. This is most likely the remains of an old, massive cluster that now has a combined mass of ~6000  M☉ . [11]

Members

The following prominent stars are considered members of the cluster with high likelihood:

Designation Spectral
type 		Visual
magnitude
α Per (33 Per) [12] F5Ib1.81
δ Per (39 Per)B5III3.01
ε Per (45 Per)B1V2.88
ψ Per [12] B5Ve4.31
HD 21278 [13] [14] B5V4.99
31 Per [12] B5V5.05
29 Per [12] [14] B3V5.16
30 Per [14] B8V5.49
34 Per B3V4.67
48 Per B3Ve4.03
HD 21699 B8 III5.49
HD 21071 [14] B7V6.09

See also

References

  1. 1 2 3 4 5 6 Kharchenko, N. V.; et al. (2013), "Global survey of star clusters in the Milky Way. II. The catalogue of basic parameters", Astronomy and Astrophysics, 558: 8, arXiv: 1308.5822 , Bibcode:2013A&A...558A..53K, doi:10.1051/0004-6361/201322302, S2CID   118548517, A53.
  2. ↑ Danner, Christopher A.; Sandquist, Eric L.; Schaefer, Gail H.; Bedin, Luigi R.; Farrington, Christopher D.; Lanthermann, Cyprien; Kraus, Stefan; Klement, Robert; Anugu, Narsireddy (2025-06-09). "Precise Age For The Binary HD 21278 In The Young Alpha Persei Cluster". The Astrophysical Journal . arXiv: 2506.08241v1 .
  3. ↑ Coyne, G. V.; et al. (March 1979), "Wavelength dependence of polarization. XXXIII - The Alpha Persei star cluster", Astronomical Journal, 84: 356–369, Bibcode:1979AJ.....84..356C, doi: 10.1086/112431
  4. ↑ "Cl Melotte 20". SIMBAD . Centre de données astronomiques de Strasbourg . Retrieved 2020-10-17.
  5. ↑ van Leeuwen, F. (2009). "Parallaxes and proper motions for 20 open clusters as based on the new Hipparcos catalogue". Astronomy & Astrophysics. 497 (1): 209–242. arXiv: 0902.1039 . Bibcode:2009A&A...497..209V. doi:10.1051/0004-6361/200811382. S2CID   16420237.
  6. ↑ Majaess, D.; et al. (2011). "Deep Infrared ZAMS Fits to Benchmark Open Clusters Hosting delta Scuti Stars". Journal of the American Association of Variable Star Observers. 39 (2): 219. arXiv: 1102.1705 . Bibcode:2011JAVSO..39..219M.
  7. 1 2 3 4 5 Lodieu, N.; et al. (August 2019). "A 5D view of the α Per, Pleiades, and Praesepe clusters". Astronomy & Astrophysics. 628: 26. arXiv: 1906.03924 . Bibcode:2019A&A...628A..66L. doi:10.1051/0004-6361/201935533. S2CID   182952614. A66.
  8. ↑ Sheikhi, Najmeh; et al. (March 2016). "The binary fraction and mass segregation in Alpha Persei open cluster". Monthly Notices of the Royal Astronomical Society. 457 (1): 1028–1036. arXiv: 1601.02186 . Bibcode:2016MNRAS.457.1028S. doi: 10.1093/mnras/stw059 .
  9. ↑ Prosser, Charles F.; et al. (October 1996). "ROSAT Pointed Observations of the Alpha Persei Cluster". Astronomical Journal. 112: 1570. Bibcode:1996AJ....112.1570P. doi: 10.1086/118124 .
  10. ↑ Paunzen, E.; Mermilliod, J.-C. "WEBDA: Alpha Persei". Universität Wien. Retrieved 2020-10-17.
  11. 1 2 Nikiforova, Victoria V.; et al. (September 2020). "The Relation of the Alpha Persei Star Cluster with the Nearby Stellar Stream". The Astronomical Journal. 160 (3): 11. arXiv: 2007.11211 . Bibcode:2020AJ....160..142N. doi: 10.3847/1538-3881/aba753 . S2CID   220686998. 142.
  12. 1 2 3 4 Zuckerman, B.; et al. (June 2012). "Stellar Membership and Dusty Debris Disks in the α Persei Cluster". The Astrophysical Journal. 752 (1): 12. arXiv: 1204.3950 . Bibcode:2012ApJ...752...58Z. doi:10.1088/0004-637X/752/1/58. S2CID   119207634. 58.
  13. ↑ Morrell, Nidia; Abt, Helmut A. (July 10, 1992), "Spectroscopic binaries in the Alpha Persei cluster", Astrophysical Journal, Part 1, 393 (2): 666–673, Bibcode:1992ApJ...393..666M, doi:10.1086/171534.
  14. 1 2 3 4 Hoogerwerf, Ronnie (March 2000), "OB association members in the ACT and TRC catalogues", Monthly Notices of the Royal Astronomical Society, 313 (1): 43–65, Bibcode:2000MNRAS.313...43H, doi: 10.1046/j.1365-8711.2000.03192.x
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