The Milky Way collision with Gaia-Enceladus, also known as Gaia Sausage, holds the key to an ancient secret: when the oldest stars in our galaxy formed.Â
Astronomers discovered recently that many of the stars in the Milky Way were already born before the huge biff. Now, these stars lie in the galaxy’s larger disk.
Here is what you need to know.
Ancient Stars, a Collision, and Deep-buried Secrets of the Universe
A team of astronomers from the University of Birmingham in the UK found that the ancient galactic collision between our galaxy and the Gaia Sausage happened approximately 10 billion years ago. What was more intriguing was that many stars had already formed before the event.Â
The team chose a bunch of red giant stars with low metallicity and realized an asteroseismological analysis of 95 of them.Â
What is asteroseismology?
Asteroseismology focuses on the pulsations of stars in their light intensity triggered by internal acoustic waves and on the oscillation frequencies.Â
Using that, astronomers found that some of the stars were almost the same age, around 10 billion years old, or even younger than those born in the Milky Way. But that’s not all.
A technique called spectroscopy helped the team figured out more things, including that the stars were actually born in the Gaia Sausage.
Spectroscopy is a fantastic tool, similar to asteroseismology, but works more humbly.
“[…] asteroseismology in combination with spectroscopy deliver precise, accurate relative ages for individual, very old, stars,” explained Andrea Miglio, an astronomer at the University of Bologna in Italy.Â
Finally, the team concluded that our galaxy had already formed a lot of its stars before the collision with Gaia Sausage. Such a thing highly supports previous discoveries that the ancient galactic biff occurred about 10 billion years ago.Â
The techniques used and the findings help astronomers’ future work by sharpening their view on the early moments of our galaxy.Â