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Colorful Stars Galore Inside a Globular Star Cluster
HST image of the Whirlpool Galaxy and companion.

NASA, ESA, and the Hubble SM4 ERO Team

NASA’s Hubble Space Telescope snapped this panoramic view of a colorful assortment of 100,000 stars residing in the crowded core of a giant star cluster.

The image reveals a small region inside the massive globular cluster Omega Centauri, which boasts nearly 10 million stars. Globular clusters, ancient swarms of stars united by gravity, are the homesteaders of our Milky Way galaxy. The stars in Omega Centauri are between 10 billion and 12 billion years old. The cluster lies about 16,000 light-years from Earth.

This is one of the first images taken by the new Wide Field Camera 3 (WFC3), installed aboard Hubble in May 2009, during Servicing Mission 4. The camera can snap sharp images over a broad range of wavelengths.

The majority of the stars in the image are yellow-white, like our Sun. These are adult stars that are shining by hydrogen fusion. The red, orange, and blue stars represent stars in a later stage of life.

All of the stars in the image are cozy neighbors. The average distance between any two stars in the cluster’s crowded core is only about a third of a light-year, roughly 13 times closer than our Sun’s nearest stellar neighbor, Alpha Centauri. Although the stars are close together, WFC3’s sharpness can resolve each of them as individual stars. If anyone lived in this globular cluster, they would behold a star-saturated sky that is roughly 100 times brighter than Earth’s sky.

Omega Centauri is among the biggest and most massive of some 200 globular clusters orbiting the Milky Way. It is one of the few globular clusters that can be seen with the unaided eye. It resembles a small cloud in the southern sky and might easily be mistaken for a comet.