NGC 6231

Open Cluster NGC 6231 (= De Chéseaux No. 9 = Lacaille II.13 = Dunlop 499 = Melotte 153 = Collinder 315), type 'g' or type 'e', in Scorpius

[NGC 6231, AAT]
Right Ascension 16 : 54.0 (h:m)
Declination -41 : 48 (deg:m)
Distance 5.9 (kly)
Visual Brightness 2.6 (mag)
Apparent Dimension 15 (arc min)

Discovered by Giovanni Batista Hodierna before 1654.

NGC 6231 has been one of the discoveries of Giovanni Batista Hodierna, published in his 1654 catalog in Palermo, but forgotten until its rediscovery in the early 1980s. It was independently rediscovered by Edmond Halley in 1678, by Philippe Loys De Chéseaux 1745-46, and by Nicholas Louis de Lacaille in 1751-52.

This cluster is extremely young, and was estimated only about 3.2 million years old. Its hottest star is of spectral type O8 and magnitude 4.71, according to the Sky Catalog 2000. It is approaching us at 22 km/sec. It belongs to the Scorpius OB association of very young stars.

The image in this page was obtained by David Malin with the 3.9-meter Anglo-Australian Telescope. This image is copyrighted and may be used for private purpose only. For any other kind of use, including internet mirroring and storing on CD-ROM, please contact the Photo Permissions Department (photo at of the Australian Astronomical Observatory.

  • More information on this image (David Malin)

    In John Caldwell's List and in the Astronomical League's Southern Sky Binocular Club List. Caldwell 76 in Patrick Moore's list.

  • Jean-Claude Mermilliod's WEBDA cluster page for NGC 6231
  • SIMBAD Data of NGC 6231
  • Publications on NGC 6231 (NASA ADS)
  • Observing Reports for NGC 6231 (IAAC Netastrocatalog)
  • NGC Online data for NGC 6231

    Hartmut Frommert
    Christine Kronberg

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    Last Modification: February 10, 2006