NGC 6231

From Wikipedia, the free encyclopedia

**NGC 6231**
Observation data: J2000.0 epoch

Class:
Constellation:	Scorpius
Right ascension:	16^h 54^m
Declination:	−41° 48′
Distance:	5.9 kly ()
Apparent magnitude (V):	2.6
Apparent dimensions (V):	15.0′
Physical characteristics
Mass:	( M_☉)
Radius:
V_HB:
Estimated age:	3.2 million years
Notable features:
Other designations:	NGC 6171, Ha. I.7, De Cheseaux 9, Lacaille II.13 Dunlop 499, Melotte 153, Collinder 315, Caldwell 76
See also: Open cluster, List of open clusters

NGC 6231 is an open cluster located near Zeta Scorpii. Zeta¹ and Zeta² Scorpii are members of this star cluster.

This cluster is estimated about 3.2 million years old, and is approaching the Solar System at 22 km/s. Very young stars including it, belong to the Scorpius OB association. Zeta¹ Scorpii (spectral type O8 and magnitude 4.71.^[1]) is hottest star in it.

It was discovered by Giovanni Batista Hodierna before 1654. Hodierna listed it as Luminosae^[2] in his catalogue of deep sky observations. This catalogue was included in his book De Admirandis Coeli Characteribuse published in 1654 at Palermo. It was independently observed some astronomers after Hodierna.