Melotte 20
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| The core of the cluster around the star α Per | |
| AladinLite | |
| Constellation | Perseus |
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Position equinox : J2000.0 |
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|---|---|
| Right ascension | 3 h 22 m |
| declination | + 49 ° 0 ′ |
| Appearance
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| Brightness (visual) | 1.2 mag |
| Angular expansion | 3 ° |
| Brightest star | α per 1.8 m mag |
| Physical data
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| distance | 601 ly |
| diameter | 30 ly |
| Age | 50–70 million years |
| history | |
| Discovery time | prehistoric |
| Catalog names | |
| OCl 392 • Mel 20 • Cr 39 | |
The α-Persei group , also Melotte 20 and Collinder 39 , is an open star cluster in the constellation Perseus that can be observed with the naked eye. The star cluster consists of a relatively large number of stars that are already visible to the naked eye around the main star of the constellation Perseus.
The brightest star in the cluster is α Per ( Mirfak ), a star of the spectral class F5 with a brightness of 1.8 mag . Other bright members are δ , ε , ψ , 29, 30, 34 and 48 Persei. The total brightness of the heap is about 1.2 mag .
Because of its size and brightness, this star cluster has been known since ancient times, like many other star clusters that are very close to Earth and therefore have a large apparent diameter (for example the Ursa Major Group or the Hyades ); however, it was not included in the modern standard Messier , NGC and IC catalogs . It was not until PJ Melotte that the cluster was included in his catalog of open star clusters in 1915. The pile can also be found in the Per Collinder catalog under the designation Cr 39 .
It is also interesting that this star cluster is a so-called motion cluster , i. H. the stars all have a similar proper motion. The stars are also physically very similar, because with a few exceptions (including α and σ Per) they are of the spectral type O or B. The cluster is part of a so-called OB association . The age of the cluster is given as around 50–70 million years.
Individual evidence
- ↑ a b c d e f α Persei group at SEDS Alpha Persei Moving Cluster, Mel 20
- ↑ van Leeuwen, F .: Parallaxes and proper motions for 20 open clusters as based on the new Hipparcos catalog , A&A , 2009 bibcode : 2009A & A ... 497..209V
- ↑ Prosser, Charles F .; Randich, Sofia; Stauffer, Joh R .; Schmitt, JHMM; Simon, Theodore: ROSAT Pointed Observations of the Alpha Persei Cluster . In: Astronomical Journal . 112, October 1996, p. 1570. bibcode : 1996AJ .... 112.1570P . doi : 10.1086 / 118124 .
- ↑ Paunzen, E., Mermilliod, J.-C. "WEBDA: Alpha Persei"