Measuring the Motions of 66 Nearby Galaxies
They’re all moving!
via SyFy
A paper recently published by a team of astronomers used Gaia to investigate these galaxies. They looked at stars in 74 dwarf galaxies in the Local Group (which includes a few whose status in the Group is unclear). Incredibly, they found what they consider to be reliable motions for 66 of them. Most are within 1.5 million light years of the Milky Way, but some are as far as 4.5 million light years from us.
Doing this is painstaking work. First, we are inside the Milky Way, so when you look toward any particular galaxy outside ours, there are local stars in the way. Sometimes it’s easy to know which galaxy they belong to, but for most it’s not. They used various schemes to figure that out (for example, looking at the colors and ages of stars to see if they make sense for the host galaxy), and were able to get enough stars in these galaxies to see the motions over the 34 months covered by the Gaia observations.
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