The Stars Of Andromeda, Inside And Out, As Revealed By Hubble
“The Hubble Space Telescope recently completed the Panchromatic Hubble Andromeda Treasury, mapping a third of Andromeda’s disk and resolving over 117 million individual stars. The most metal-rich stars are found near the central bulge, with the newest, bluest stars found in the open clusters. Far outside of the center, in the outer disk and the faint galactic halo, a different set of populations thrive.”
If you want to know what types of stars are found all throughout a galaxy, looking at our own simply won’t do: too much of it is obscured by the plane and our position within it. But there’s an even more impressive galaxy – Andromeda – just 2.5 million light years away. And thanks to the power of the Hubble Space Telescope, we’ve not only resolved individual stars within it, we’ve resolved over a hundred million of them. But when we look towards the center versus at the outskirts of the disk, or even into the halo, we find something very, very different: older, redder, fainter and less-evolved stars. Even more spectacularly: beyond them, a rich slew of distant galaxies, visible out to distances exceeding a billion light years.