data from Messier 71
|Till Credner and Sven Kohlen, Calar Alto Observatory|
equinox : J2000.0 , epoch : J2000.0
|Right ascension||19 h 53 m 46.11 s|
|declination||+ 18 ° 46 ′ 42.3 ″|
|Concentration class||X to XI|
|Brightness (visual)||6.1 mag|
|Brightness (B-band)||7.91 mag|
|Angular expansion||7.2 '|
|Integrated spectral type||G1|
|Redshift||(−267 ± 17) · 10 −6|
|Radial velocity||−80 ± 5 km / s|
(4 kpc )
|discovery||J.-P. de Chéseaux|
|M 71 • NGC 6838 • C 1951 + 186 • GCl 115 • Mel 226 • Cr 409|
Messier 71 (also referred to as NGC 6838 ) is a +6.1 mag bright globular cluster with an angular extent of 7.2 'in the constellation Arrow . About 13,000 light years away, it belongs to the inner galactic halo and has a diameter of only 36 light years.
Its stars have a metallicity of a fifth of the solar value, while most globular clusters only have a hundredth of the metal abundance. It also contains very few variable stars and none of the RR Lyrae-type , which is also very unusual for a globular cluster. This is explained by the relatively young age of only 9-10 billion years for a globular cluster. Only NGC 104 and M 68 show similar values .
The object may have been discovered by de Chéseaux in 1745 or by J. Köhler around 1775. Méchain made reliable observations in June 1780 and informed Messier, who included the star cluster in his catalog that same year.
The classification of M71 as a globular cluster has long been considered controversial because the cluster is quite loose. The cluster was therefore mostly categorized as a very dense open star cluster .
An instrument with a lens diameter of at least six inches is recommended to observe the object.
- astronews.com: Picture of the day May 29, 2012
- NASA / IPAC Extragalactic Database
- Messier 71 at SEDS
- Klaus-Peter Schröder: Stars and Space July 2008 p. 81
- Klaus-Peter Schröder: Stars and Space July 2014 p. 65f
- Robert Burnham Jr.: Burnham's Celestial Handbook Volume Three, Dover Publications New York (c) 1978, p. 1544 and 1545, ISBN 0-486-23673-0