In a new study, scientists have broken down light from 600,000 stars into spectra that determine the chemical composition of the stars. In this way, they were able to reveal which groups of stars are at home in the Milky Way and which are intruders with other galactic origins.
“The Milky Way ate many smaller galaxies but, until recently, we didn’t have enough evidence to say for sure,” said Sven Buder, an astrophysicist at the Australian National University in Canberra and lead author of the new study. “This is because the simple images of the stars in our Milky Way look the same, whether they were born inside the galaxy or outside and then mixed in the galaxy.”
For some time, data from the European Space Agency’s (ESA) Gaia mission showing patterns of star movement have indicated that there are many populations of stars in the Milky Way that were not born there. These data showed that some groups of stars are moving in different directions than the rest, suggesting that they may have come from outside the galaxy.
Buder and his collaborators used the Anglo-Australian Telescope (AAT), a 3.9-meter optical telescope at the Australian Astronomical Observatory in Sydney, to divide the light from those stars into an individual color spectrum. By studying these colored spectra, scientists can see the different chemical compositions of the observed stars.
“By ‘scanning’ these star barcodes, we measured how abundant 30 elements were, such as sodium, iron, magnesium and manganese, and how they appeared in different concentrations depending on where the star was born,” Buder explained in declaration.
Stars that originated in the Milky Way appear greener, scientists said in the statement, while those from the outside glow in more yellow hues. Astronomers believe that understanding the origins of stellar populations in the Milky Way may help solve further mysteries of the galaxy’s structure and composition.
The catastrophic collisions that a few billions of years ago mixed the Milky Way with other galaxies may have pushed the stars in a way that we can still see today. Astronomers know that in the belt of the Milky Way, which is visible in the night sky from Earth, older stars are separated from younger ones, but they haven’t yet figured out why.
“When we look [la Via Lattea], we are looking at two populations of stars, one much older than the other, ”said Buder. “The old stars have moved to appear to protrude from the main plane of the Milky Way, while the younger stars form a much thinner band in the plane.” He added that past galactic collisions may have been the cause of these two groups of stars being separated in this way. Although the Milky Way is our home galaxy, we still don’t understand how it formed and evolved, ”she said.
