This is what 100,000 stars look like. They’re just a fraction of the 10 million stars in the massive globular cluster Omega Centauri, where the stars are packed so closely, it’s only around a third of light year to get from one to the next.
The colors are Hubble’s way of showing off its new camera, the Wide Field Camera 3. From their release:
The photograph showcases the camera’s color versatility by revealing a variety of stars in key stages of their life cycles.
The majority of the stars in the image are yellow-white, like our Sun. These are adult stars that are shining by hydrogen fusion. Toward the end of their normal lives, the stars become cooler and larger. These late-life stars are the orange dots in the image.
Even later in their life cycles, the stars continue to cool down and expand in size, becoming red giants. These bright red stars swell to many times larger than our Sun’s size and begin to shed their gaseous envelopes.
After ejecting most of their mass and exhausting much of their hydrogen fuel, the stars appear brilliant blue. Only a thin layer of material covers their super-hot cores. These stars are desperately trying to extend their lives by fusing helium in their cores. At this stage, they emit much of their light at ultraviolet wavelengths.
When the helium runs out, the stars reach the end of their lives. Only their burned-out cores remain, and they are called white dwarfs (the faint blue dots in the image). White dwarfs are no longer generating energy through nuclear fusion and have gravitationally contracted to the size of Earth. They will continue to cool and grow dimmer for many billions of years until they become dark cinders.
Other stars that appear in the image are so-called “blue stragglers.” They are older stars that acquire a new lease on life when they collide and merge with other stars.
The pale blue ones – they’re the eaters.
Image from the newly revamped Hubble Space Observatory.