Can you count all the stars here? NASA says there are 100,000, all squeezed (relatively speaking) into a small portion of the Omega Centauri star cluster. The yellow-white dots are adult stars powered by hydrogen fusion, the orange ones are late-life stars, and the red giants, which are shedding their gaseous envelopes, are older still.
The brilliant blue dots are stars that have ejected most of their mass and spent much of their hydrogen, and "are desperately trying to extend their lives by fusing helium in their cores," NASA says. "At this stage, they emit much of their light at ultraviolet wavelengths." The faint blue dots are white dwarfs--stars that have run out of helium and are now just burnt-out and have ever cooler cores.
Omega Centauri is among the approximately 200 globular clusters that orbit the Milky Way, and it's one of the most massive, host to nearly 10 million stars. It lies 16,000 light-years away from us.
Photo by NASA, ESA, and the Hubble SM4 ERO Team
Caption by Jonathan Skillings
