Omega Centauri

NGC 5139, Caldwell 80

Image exposure:
61 minutes
Image field of view:
31.9 x 20 arcmin
Image date:

Omega Centauri is the visually brightest, most massive and largest globular cluster of all the 150 globular clusters which are known to be orbiting around the Milky Way in the galactic halo. About 10 million stars are packed into a volume radius of only 135 light years.

The best way I can find of comparing that star density with our own region in space is from these Wikipedia pages, which lists the number of stars systems within a (smaller) volume radius of up to 80 light years of the Sun as just 1,145.

What an amazing sight it would be, living on a planet near – but not too near* – to the cluster’s core, where stars are estimated to average a distance of only 0.1 light-year away from each other!

*It is also suspected that an intermediate mass black hole may exist at the centre of the cluster.

The night sky would shine brilliantly and the locals would almost certainly have barely any information about the cosmos beyond the cluster itself. Amateur astronomers would see little except a sky full of incredibly bright stars and maybe just a hint of the Milky Way beyond.

The unusually high level of heavy elements in its stars (compared to other globular clusters) have led astronomers to suspect that Omega Centauri is the surviving nucleus of a dwarf spheroidal galaxy which was gravitationally captured and stripped of its outer regions by close encounters with the Milky Way galaxy. The fact that Omega Centauri orbits in retrograde (in the opposite direction to the rotation of the Milky Way) supports this theory.

Omega Centauri is visible to the naked eye as a faint and fuzzy patch in a dark sky, if you live far enough south and you know where to look.

Visual magnitude: +3.7
Apparent extended diameter 55 arc-min (almost two moon-widths).
Actual diameter 270 light years.
Distance 17,000 light years.

In The Sky Down Under

Centaurus and Omega Centauri
Telescope:Meade LX-90 200mm Schmidt-Cassegrain
(deforked); 2000 mm f/l @ f/10.
Optics:Astronomik light pollution filter.
Mount & Guiding:SkyWatcher EQ6-R Pro mount.
Imaging camera:ZWO ASI 071 MC cooled.

The Blind Astronomer

Cosmic Focus Observatory

34° South

Above us only sky….

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Images © Roger Powell

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ABOVE US ONLY SKY : amateur astronomy in australia


  1. Interesting post and great image !
    Globular clusters make great subjects for amateurs to images. Many members of my local astronomy society (in north west England) have taken some great images of Messier 13, but sadly Omega Centauri at declination -47.5 degrees isn’t visible from where I live 😊

    It’s an interacting thought to inhabit a planet inside the globular cluster 😉 but, in reality the high density of stars would mean that planetary orbits would be constantly disrupted and it is unlikely that planets could exist long enough in the “Goldilocks Zone” for life to have evolved

    Liked by 1 person

    1. Whilst we still don’t know whether alien civilisations have ever existed in or around the galaxy, I suspect they may be tenuous at best. So I think you are right, Steve. Dense regions such as globular clusters and galactic cores (of which Omega Centauri possibly once was), would be the last regions we might expect to find evidence of rare advanced life.



  2. Given my experience in dense traffic, I suspect a dense globular cluster wouldn’t be much of a picnic to live in. Plus, you’d have to have really heavy drapes to get any sleep at all.

    Liked by 1 person

    1. I imagine the physics would be the same, with just a few more variables.

      Besides, 0.1 lightyears is still a lot of space … 659,444,498,664 and a tad miles between bodies

      Liked by 1 person

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