NGC 5139

Globular cluster NGC 5139 (= De Chéseaux No. 18 = Lacaille I.5 = Dunlop 440 = Bennett 61), class VIII, in Centaurus

Omega Centauri

[NGC 5139, AAT]
Right Ascension 13 : 26.8 (h:m)
Declination -47 : 29 (deg:m)
Distance 16.0 (kly)
Visual Brightness 3.68 (mag)
Apparent Dimension 36.3 (arc min)

Discovered by Edmond Halley in 1677.

This is the biggest of all globular clusters in our Milky Way galaxy. With its about 5 million solar masses, it is about 10 times as massive as other big globulars, and has about the same mass as the smallest whole galaxies. It is also the most luminous Milky Way globular, and the brightest globular cluster in the sky. In the Local Group, it is outshined only by the brightest globular cluster G1 in the Andromeda Galaxy M31.

In 1999, a team led by Young-Wook Lee of Yonsei University, South Korea, obtained a color-magnitude diagram (CMD) for 50,000 member stars of Omega Centauri with the 0.9-m telescope of CTIO in Chile. Studies of this CMD indicate that the stars of this cluster did not all form at once but over a 2-billion-year period of time, with several starburst peaks. This was the first time that multiple populations were found in a globular cluster. The team who carried out this work speculates that this result may indicate that Omega Centauri might be the remnant of a nucleus of a small galaxy which has merged with our Milky Way.

The image in this page 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 of the Australian Astronomical Observatory.

  • More information on this image by David Malin

    Omega Centauri had been listed in Ptolemy's catalog as a star. Halley was the first to document its nonstellar nature, and listed it as "luminous spot or patch in Centaurus" in his historical list of six such objects. Lacaille included it in his catalog as number I.5.

    In the SAC 110 best NGC object list. In John Caldwell's observing list. In the Astronomical League's Southern Sky Binocular Club list. Caldwell 80.

  • Multispectral Image Collection of Omega Centauri, SIRTF Multiwavelength Messier Museum
  • Marco Castellani's data for NGC 5139
  • Christine Clement's Catalog of Variable Stars in NGC 5139
  • SIMBAD Data of NGC 5139
  • Publications on NGC 5139 (NASA ADS)
  • Observing Reports for NGC 5139 (IAAC Netastrocatalog)
  • NGC Online data for NGC 5139

    Hartmut Frommert
    Christine Kronberg

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    Last Modification: January 23, 2014