| NGC 6231 | |
|---|---|
| Observation data (J2000.0 epoch) | |
| Constellation | Scorpius |
| Right ascension | 16h 54m |
| Declination | −41° 48′ |
| Distance | 5.9 kly |
| Apparent magnitude (V) | 2.6 |
| Apparent dimensions (V) | 15.0′ |
| Physical characteristics | |
| Estimated age | 3.2 million years |
| 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 (HR 6262) is a member of this star cluster. (Its brighter apparent partner, Zeta2 (HR 6271), is only 150 ly from Earth and so is not a cluster member.)
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 OB1 association. Zeta1 Scorpii (spectral type O8 and magnitude 4.71.[1]) is the 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 by other astronomers after Hodierna.
Coordinates: 16h 54m 00s, +41° 48′ 00″
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