After 1,000 days in orbit, the European Space Agency’s Gaia satellite has come up with the most detailed map of space ever, showing 1.14 billion stars in our Milky Way galaxy, the agency says.
The ESA’s annotated version of the map (below) explains what on Earth (or, really, not on Earth) you’re looking at.
The bright areas are crammed with stars, while darker patches are regions where Gaia didn’t pick up so many. That bright disc of stars across the picture is called the “Galactic Plane,” where most of the galaxy’s stars lie, and it’s “about 100,000 light-years across and about 1,000 light-years thick,” the ESA explains.
The dark, wispy shapes across the middle of the Galactic Plane are “clouds of inter-stellar gas,” the ESA writes, which soak up starlight to imprint their eery shape on the picture.
The “globular clusters” and “open clusters” in the annotated map are groups of stars clinging together with shared gravity. “Globular clusters” hold hundreds of thousands or even millions of aging stars and sit in the “halo” of the galaxy, which the ESA says is a round structure that encompasses most of the galaxy with a 100,000 light-year radius. The “open clusters” are smaller collections of hundreds to thousands of stars.
The two shapes bursting with light on the bottom right of the Galactic Plane are a pair of dwarf galaxies that orbit the Milky Way, and you can get a peek of our nearest galactic neighbor Andromeda just below and to the left of the Plane. It’s only a neighbor in the galactic sense though–Andromeda is around 2.5 million light-years away.
And what are those weird stripey patches all over the picture? Well, they’re not part of the galaxy at all but a residue of Gaia’s “scanning procedure,” the ESA explains, promising that they’ll fade away as Gaia scans more and more in its five-year quest.