Messier 55
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Globular cluster Messier 55 |
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| Image taken with the ESO 3.6 m telescope at the La Silla Observatory | |
| AladinLite | |
| Constellation | Sagittarius |
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Position equinox : J2000.0 , epoch : J2000.0 |
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| Right ascension | 19 h 40 m 00 s |
| declination | −30 ° 57.9 ′ |
| Appearance | |
| Concentration class | XI |
| Brightness (visual) | 7.42 mag |
| Brightness (B-band) | 8.12 likes |
| Angular expansion | 19 ′ |
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Color excess E (BV) (redness) |
0.07 |
| Physical data | |
| Affiliation | Milky Way |
| Integrated spectral type | F4 |
| Redshift | +0.000584 ± 0.000001 |
| Radial velocity | (+174.9 ± 0.4) km / s |
| distance | 17.3 kLj (5.3 kpc ) |
| diameter | 100 ly |
| Concentration lg (r t / r c ) | 0.76 |
| Metallicity [Fe / H] | −1.81 |
| history | |
| discovery | Nicolas Louis de Lacaille |
| Discovery date | 1751 |
| Catalog names | |
| M 55 • NGC 6809 • C 1936-310 • GCl 113 • | |
Messier 55 (also known as NGC 6809 ) is a 7.4 mag bright globular cluster with an angular extent of 19 ′ in the constellation Sagittarius . Its diameter is around 100 light years and is around 17,000 light years away from us.
The 100,000 stars that make up Messier 55 add up to around 270,000 solar masses . What is special about these stars is not only that they are crowded together in a comparatively small volume, they are also some of the oldest stars in the universe at around ten billion years old . They emerged almost simultaneously from a gas cloud in the early days of our Milky Way and consist mainly of hydrogen and helium . Heavier elements like oxygen and nitrogen were much rarer at the time than they are today.
Because of its southern position, this star cluster is difficult to find from Central Europe.
The first documented observations of this celestial object were made in 1751 by the French astronomer Nicolas Louis de Lacaille . Charles Messier added the star cluster to his catalog 26 years later.
Web links
- M55 at SEDS (English)
- ESO: VISTA peek at a giant ball of stars May 9, 2012
- astronews.de: Picture of the day October 9, 2013
- Spektrum.de : Amateur recordings [1]
Individual evidence
- ↑ a b c d SIMBAD
- ^ NED data for the Messier Objects
- ↑ a b SEDS
- ↑ a b M55: Globular Star Cluster ( Astronomy Picture of the Day of September 18, 2004)
- ↑ https://cseligman.com/text/atlas/ngc68.htm#6809
- ↑ http://www.eso.org/public/germany/news/eso1220/
- ↑ Benjamin Knispel: Star Ball in Sagittarius; in: Stars and Space , July 2012, p. 12
