Washington, April 11 : NASA's Spitzer Space Telescope has observed millions of clustered stars glistening like a shining opal in the constellation Centaurus.

Called Omega Centauri, this sparkling orb of stars is like a miniature galaxy and is the biggest and brightest of the more than 150 similar objects, called globular clusters, which orbit around the outside of the Milky Way galaxy.

While the visible-light observations highlight the cluster's millions of jam-packed stars, Spitzer's infrared telescope revealed the dustier, more evolved stars tossed throughout the region.

"Now we can see which stars form dust and can begin to understand how the dust forms and where it goes once it is expelled from a star," said Martha Boyer of the University of Minnesota.

Globular clusters are some of the oldest objects in our universe. Their stars are more than 12 billion years old, and, in most cases, formed all at once when the universe was just a toddler.

Omega Centauri is unusual in that its stars are of different ages and possess varying levels of metals, or elements heavier than boron.

According to astronomers, this points to a different origin for Omega Centauri than other globular clusters: they think it might be the core of a dwarf galaxy that was ripped apart and absorbed by our Milky Way long ago.

In the new picture of Omega Centauri, the red- and yellow-colored dots represent the stars revealed by Spitzer. These are the more evolved, larger, dustier stars, called red giants. The stars colored blue are less evolved, like our own sun, and were captured by Spitzer.

Some of the red spots in the picture are distant galaxies beyond our own.

"As stars age and mature into red giants, they form dust grains, which play a vital role in the evolution of the universe and the formation of rocky planets," said Jacco van Loon, the study's principal investigator at Keele University in England.

"Spitzer can see this dust, and it was able to resolve individual red giants even in the densest central parts of the cluster," he added.

ANI