Melotte 111
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| Photo of Berenike's hair. The orange star at the top left (north direction) is γ Com. A version of the picture with coordinate lines can be found here . | |
| AladinLite | |
| Constellation | Berenike's hair |
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Position equinox : J2000.0 |
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| Right ascension | 12 h 23 m |
| declination | + 25 ° 51 ′ |
| Appearance
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| Brightness (visual) | 1.8 mag |
| Angular expansion | 270 ' |
| Number of stars | 37 |
| Brightest star | γ Com, +4.3 m mag |
| Physical data
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| distance | 288 ly |
| diameter | 20 ly |
| Age | 400 million years |
| history | |
| Catalog names | |
| C 1222 + 263 • OCl 588 • Mel 111 • Cr 256 • | |
Melotte 111 or the Coma Berenices star cluster is an open star cluster in the constellation Haar der Berenike that can be observed with the naked eye. With its 37 individual stars, the star cluster forms the main part of the constellation Haar der Berenike . In addition, the impression of this star cluster with the naked eye probably gave the constellation its name.
The extent of the star cluster is about 4.5 °, or - at a distance of 288 light years - about 20 light years. Its age is estimated to be 500 million years based on its star population .
The total mass of the object is estimated to be only 100 solar masses , and the resulting mass density only exceeds the value of the solar environment by a factor of 3. Such a low-mass and loosely structured star cluster can only survive longer if it is outside the galactic plane.
The brightest star in the cluster is γ Com with a brightness of 4.3 mag , the total brightness of the cluster is about 1.8 mag . The cluster does not contain any stars weaker than 10.5 mag . One possible explanation for this is that the smallest members of this cluster have already escaped, because the smallest gravitational impact from outside causes it to lose its low-mass (and weakest) stars. Therefore it is to be expected that Melotte 111 will completely dissolve within the next galactic rotation (approx. 220 million years).
Because of its size and brightness, this star cluster has been known since ancient times and was first cataloged by Ptolemy. Like many other star clusters that are very close to Earth and therefore have a large apparent diameter (e.g. the Ursa Major group or the Hyades ), it was not included in the modern standard catalogs Messier , NGC and IC added. It was not until PJ Melotte that the cluster was included in his catalog of open star clusters in 1915 . The heap can also be found in the Per Collinder catalog under the designation Cr 256 .
The star cluster is a so-called motion cluster , i. H. the stars all have a similar proper motion (on average −12.4 mas in right ascension and −9.4 mas in declination ). However, since the mean value of the proper movements is almost exactly tangential (mean radial speed −1.17 km / s), this movement (in contrast to the well-known example of the Hyades ) does not allow a simple determination of the distance through the star current parallax.
Individual evidence
- ↑ a b c d http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=melotte+111&submit=SIMBAD+search
- ↑ Stars and Space April 2006, p. 60