Caldwell 80

Better known as Omega Centauri, Caldwell 80 is home to around 10 million stars.


17,000 light-years

Apparent Magnitude




object type

Globular Cluster

This Hubble image shows off 2 million members of the biggest and brightest ball of stars in our galaxy. Caldwell 80, also known as NGC 5139 and commonly called Omega Centauri, is home to around 10 million stars.
NASA, ESA, and the Hubble Heritage Team (STScI/AURA); Acknowledgment: A. Cool (San Francisco State University) and J. Anderson (STScI)

This Hubble image shows off 2 million members of the biggest and brightest ball of stars in our galaxy. Caldwell 80, also known as NGC 5139 and commonly called Omega Centauri, is home to around 10 million stars. Located about 17,000 light-years away from Earth toward the Centaurus constellation, the cluster has a diameter of about 450 light-years. This image, taken with the Advanced Camera for Surveys in 2002, covers a region only about 50 light-years across.

This Hubble image, which includes ultraviolet and visible light captured by the Wide Field and Planetary Camera 2 in 1997, zooms in on the center of Caldwell 80 (Omega Centauri). The image resolves about 50,000 stars in a region about 13 light-years across.
NASA/ESA and the Hubble Heritage Team (STScI/AURA); Acknowledgment: A. Cool (SFSU)

Globular clusters like this one are spherical groups of mostly old, low-mass stars that are bound together by gravity. Omega Centauri has always been a bit of a black sheep since it has several characteristics that set it apart. In addition to it being the most massive globular cluster in our galaxy, it also includes stars of various ages, whereas other globular clusters typically contain stars from only one generation. What’s more, observations using Hubble and ground-based telescopes indicate that there is a black hole at the center of the cluster. This suggests that Omega Centauri may not be a globular cluster after all — it might actually be a dwarf galaxy that has somehow been stripped of its outer stars.

Omega Centauri has been known since at least the time of the ancient astronomer Ptolemy, though he thought the cluster was a star. English astronomer Edmund Halley classified it as a nebulous object in 1677. Omega Centauri was finally correctly identified as a star cluster by another English astronomer, John Herschel, in 1836.

With a magnitude of 3.7, Omega Centauri is often considered the most dazzling globular cluster in the sky. It’s so bright that it can easily be seen with the unaided eye, though binoculars or a telescope will reveal an especially breathtaking spectacle. The cluster is a favorite observing target for amateur astronomers, but it is only visible to observers at low northern latitudes and south of the equator. Autumn skies in the Southern Hemisphere will present the best opportunity to observe it.

Hubble’s Wide Field Camera 3 captured this image in ultraviolet and visible light showing 100,000 stars in the core of Caldwell 80 (Omega Centauri) soon after the camera was installed in 2009. The stars’ colors give us information about them. Bright blue stars are old, hot stars that are fusing helium in their cores. Bright red stars are cool giants that are heading into old age. Dimmer red stars are cool dwarfs destined to live for a long time. White stars are typically middle-aged, average stars.
NASA, ESA, and the Hubble SM4 ERO Team
This star chart for Caldwell 80 represents the view from mid-southern latitudes for the given month and time.
Image courtesy of Stellarium


Dwarf Galaxy - A small, faint galaxy with only millions to a few billion stars.

Globular Cluster - A spherical group of stars that are gravitationally bound to each other, with most of the stars concentrated at the cluster’s center.

Magnitude - The brightness of an astronomical object, represented by a number; bright objects have low numbers on the magnitude scale, while dim objects have high numbers.

Explore Hubble's Caldwell Catalog

The following pages contain some of Hubble’s best images of Caldwell objects.

Stars with four diffraction spikes dot the scene against a black backdrop.

Caldwell 1

Also known as NGC 188, this group of stars formed from a large cloud of gas making the stars roughly…

Red cloud of dust with a bright white star in the center of it. Lots of reddish and orangish stars in the background.

Caldwell 2

This shell of gas is expanding outward, away from the dying star within.

Large grouping of bright white, blue and red stars. Lightly colored blue dust surrounds the stars.

Caldwell 3

This barred spiral galaxy was first spotted by British astronomer William Herschel in April 1793 in the constellation Draco.