NGC 4755 (Kappa Crucis) (original) (raw)

Open ClusterNGC 4755(= Lacaille II.12 = Dunlop 301), type 'g', in Crux

Kappa Crucis, Jewel Box

[ ](../../Pics/Ngc/n4755aat.jpg)

Discovered by Nicholas Louis de Lacaille on March 25, 1752.

This cluster was one of the finest open clusters discovered by Nicholas Louis de Lacaille when he was in South Africa during 1751-1752.

This cluster is one of the youngest known, with an estimated age of only 7.1 million years (Sky Catalog 2000). Its hottest star is of spectral type B0. According to Burnham, the 3 brightest stars are blue giants of mag 5.75 and spectral type B9, mag 5.94 and type B3, and mag 6.80/B2, while the fourth brightest star is a mag 7.58 M2 red supergiant. Another mag 5.7/spectral type A1 star is probably also a member, another white supergiant: This star would be the brioghtest of the cluster at about absolute magnitude -7.7 (83,000 solar luminosities).

Situated close to the cluster is a huge dark area of the sky, right within the band of the Milky Way: the Coal Sack. This is a huge dark nebula, probably the nearest at 500 to 600 light years distance, and 60 to 70 light years diameter.

Our image was obtained by David Malin with the 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 aaoepp.aao.gov.au) of the Australian Astronomical Observatory.

• More information on this image by David Malin
  In the Astronomical League's Southern Sky Binocular Club list. In John Caldwell's List.Caldwell 94.
• Jean-Claude Mermilliod's WEBDA cluster page for NGC 4755
• SIMBAD Data of NGC 4755
• Publications on NGC 4755 (NASA ADS)
• Observing Reports for NGC 4755 (IAAC Netastrocatalog)
• NGC Online data for NGC 4755

Hartmut Frommert
Christine Kronberg
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Last Modification: March 22, 1998