Home Science The Oldest Stars in Our Galaxy Predate The Gaia Sausage, Astronomers Find

The Oldest Stars in Our Galaxy Predate The Gaia Sausage, Astronomers Find

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A new technique for deciding the ages of stars in the Milky Way has provided us tighter constraints for an historical galactic collision.

By intently inspecting the interior oscillations and chemical composition of 95 purple giant stars, a crew of astronomers led by the University of Birmingham in the British isles has established that the Milky Way’s biff with a mysterious small galaxy regarded as Gaia-Enceladus, or the Gaia Sausage, took spot close to 10 billion years back.

 

They also uncovered that many of the stars in the Milky Way experienced by now shaped prior to this merger now, these unique stars can mostly be identified in the thick disk of the galaxy, the greater of the Milky Way’s two disk structures.

“The chemical composition, area and motion of the stars we can observe now in the Milky Way contain precious details about their origin,” explained astronomer Josefina Montalbán of the University of Birmingham in the Uk.

“As we raise our knowledge of how and when these stars were being formed, we can start out to much better comprehend how the merger of Gaia-Enceladus with the Milky Way impacted the evolution of our galaxy.”

The Milky Way has had a pretty violent time in excess of the 13.6 billion yrs or so considering the fact that it shaped. It has consistently gobbled up lesser galaxies, appropriating their stars as its personal.

The ongoing Gaia study, which is mapping the Milky Way in 3D, has disclosed these collisions in the motions of the stars and, as much as we can tell so considerably, the major of the galaxies slurped up by the Milky Way was the Gaia Sausage.

 

For additional granular depth about this incident, nevertheless, you have to have additional than the motions of the stars, as revealing as those people can be. Recognizing the ages and chemical compositions can aid far too, since they can enable decide wherever the stars ended up born.

A star’s chemical composition can assistance do the job out its age – more youthful stars have additional major features than more mature kinds, or larger metallicity, because metals didn’t exist right before stars arrived together and solid them via nuclear fusion and supernova explosions. These compositions are identified using spectroscopy, wanting for modifications in unique wavelengths that indicate sure components are existing.

Spectroscopy is a fairly terrific resource but for even increased precision, the analysis team turned to asteroseismology.

Asteroseismology is the analyze of the oscillation frequencies of stars, or pulsations in their light intensity driven by inside acoustic waves. These oscillations are carefully linked to the houses of the star’s interior, this sort of as its density and acoustic profile in convert, these are related to the star’s mass and age.

Now-retired world-looking telescope Kepler was optimized to search for adjustments in star brightness, given that that is a person way we can detect exoplanets orbiting them. It gathered asteroseismological knowledge on a whole bunch of stars from these, Montalbán and her workforce picked a bunch of crimson large stars with small metallicity, considering that these are extended-lived and intrinsically bright, which would make them superb for mapping star ages.

 

They then performed an asteroseismological evaluation of 95 of them, concentrating on the specific stars alternatively of averaging out their homes.

The spectroscopy discovered that some of the stars originated in the Gaia Sausage, and the asteroseismology revealed these ended up all around the identical age, about 10 billion several years previous, or slightly more youthful, than the stars that fashioned appropriate in this article in the Milky Way.

This indicates the Milky Way experienced currently shaped a good amount of its stars, and was executing so competently, just before the merger with the Gaia Sausage. This supports former findings that the Milky Way-Gaia Sausage infall took spot close to 10 billion several years back, the researchers mentioned.

“We have shown the massive likely of asteroseismology in combination with spectroscopy to provide precise, accurate relative ages for personal, incredibly aged, stars,” reported astronomer Andrea Miglio, of the College of Bologna in Italy.

“Taken alongside one another, these measurements add to sharpen our perspective on the early yrs of our Galaxy and assure a dazzling long term for Galactic archeoastronomy.”

The investigate has been printed in Nature Astronomy.

 





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