A new approach for analyzing the ages of stars in the Milky Way has provided us tighter constraints for an ancient galactic collision.
By closely analyzing the inside oscillations and chemical composition of 95 red giant stars, a team of astronomers led by the College of Birmingham in the United kingdom has determined that the Milky Way’s biff with a mysterious smaller galaxy known as Gaia-Enceladus, or the Gaia Sausage, took put all around 10 billion a long time back.
They also identified that several of the stars in the Milky Way had by now shaped prior to this merger now, these initial stars can typically be discovered in the thick disk of the galaxy, the much larger of the Milky Way’s two disk buildings.
“The chemical composition, site and movement of the stars we can notice now in the Milky Way have valuable data about their origin,” explained astronomer Josefina Montalbán of the College of Birmingham in the Uk.
“As we raise our knowledge of how and when these stars were being fashioned, we can start off to better understand how the merger of Gaia-Enceladus with the Milky Way affected the evolution of our galaxy.”
The Milky Way has experienced a really violent time about the 13.6 billion a long time or so since it formed. It has frequently gobbled up lesser galaxies, appropriating their stars as its have.
The ongoing Gaia study, which is mapping the Milky Way in 3D, has discovered these collisions in the motions of the stars and, as much as we can inform so significantly, the most significant of the galaxies slurped up by the Milky Way was the Gaia Sausage.
For a lot more granular depth about this incident, though, you have to have far more than the motions of the stars, as revealing as those people can be. Figuring out the ages and chemical compositions can enable too, given that they can support identify wherever the stars were being born.
A star’s chemical composition can aid perform out its age – youthful stars have much more weighty elements than older ones, or higher metallicity, because metals didn’t exist before stars arrived along and solid them through nuclear fusion and supernova explosions. These compositions are identified utilizing spectroscopy, wanting for modifications in precise wavelengths that indicate selected things are present.
Spectroscopy is a very great instrument but for even increased precision, the research crew turned to asteroseismology.
Asteroseismology is the review of the oscillation frequencies of stars, or pulsations in their light intensity pushed by inner acoustic waves. These oscillations are closely linked to the qualities of the star’s inside, such as its density and acoustic profile in change, these are relevant to the star’s mass and age.
Now-retired earth-hunting telescope Kepler was optimized to lookup for adjustments in star brightness, due to the fact that is one particular way we can detect exoplanets orbiting them. It collected asteroseismological info on a full bunch of stars from these, Montalbán and her crew picked a bunch of crimson large stars with lower metallicity, because these are extensive-lived and intrinsically brilliant, which helps make them exceptional for mapping star ages.
They then done an asteroseismological assessment of 95 of them, focusing on the particular person stars as a substitute of averaging out their homes.
The spectroscopy revealed that some of the stars originated in the Gaia Sausage, and the asteroseismology exposed these were being all all over the exact same age, about 10 billion years aged, or a bit younger, than the stars that formed right below in the Milky Way.
This suggests the Milky Way experienced by now shaped a good quantity of its stars, and was executing so effectively, right before the merger with the Gaia Sausage. This supports earlier conclusions that the Milky Way-Gaia Sausage infall took spot all around 10 billion a long time back, the researchers explained.
“We have revealed the massive prospective of asteroseismology in mixture with spectroscopy to supply exact, correct relative ages for particular person, really outdated, stars,” mentioned astronomer Andrea Miglio, of the University of Bologna in Italy.
“Taken alongside one another, these measurements add to sharpen our check out on the early a long time of our Galaxy and assure a vibrant upcoming for Galactic archeoastronomy.”
The investigation has been published in Mother nature Astronomy.