Cosmology: Milky Way is ancient, with a new history (Introduction)

by David Turell , Monday, May 17, 2021, 19:38 (1287 days ago) @ David Turell

Another set of findings:

https://www.sciencenews.org/article/milky-way-galaxy-origins-merger-collision-star-age

"The Milky Way as we know it today was shaped by a collision with a dwarf galaxy about 10 billion years ago. But most of the modern galaxy was already in place even at that early date, new research shows.

"Ages of stars left behind by the galactic interloper are a bit younger or on par with stars in the Milky Way’s main disk, researchers report May 17 in Nature Astronomy. And that could mean that the Milky Way grew up faster than astronomers expected, says study author Ted Mackereth, an astrophysicist at the University of Toronto.

“'The Milky Way had already built up a lot of itself before this big merger happened,” he says.

***

"The team selected about 95 stars that had been observed by NASA’s exoplanet-hunting Kepler space telescope, which ended its mission in 2018 (SN: 10/30/18). Six of those stars were from Gaia-Enceladus/Sausage, and the rest were from the Milky Way’s thick disk. By measuring how the brightnesses of those stars fluttered over time, Mackereth and colleagues deduced ages with about 11 percent precision.

"The Gaia-Enceladus/Sausage stars are slightly younger than the Milky Way stars, but all were pretty close to 10 billion years old, the team found. That suggests that a large chunk of the Milky Way’s disk was already in place when Gaia-Enceladus/Sausage came crashing through. It’s still possible that the incoming galaxy sparked the formation of some new stars, though, Mackereth says. To tell how much, they’ll need to get ages of a lot more stars."

Comment: Not surprising news. The Milky Way is big and very old and grew by gobbling up smaller galaxies. What is amazing is how much we can learn now by startgazing.