Out-of-place star confirms Milky Way’s cannibal past

Astronomers have confirmed the nefarious and bloodthirsty past of our Milky Way galaxy as a serial cannibal, consuming smaller stellar islands that cross its path.

The confirmation comes in the form of a star called v Indi, which is visible in our southern skies, that is older than our galaxy – leading astronomers to believe that the stranger sun was left behind in a previous collision with another galaxy.

The extreme age of the sojourner star – 11 billion years – also pinpoints the date of the fender bender with a smaller galaxy, putting it between 11.6 and 13.2 billion years ago.

“Over the course of its history, the Milky Way has ingested multiple smaller satellite galaxies,” astronomers say in a paper published recently.

“It is difficult in general to date precisely the age at which any one merger occurred,” they continue, “but recent results have revealed a population of stars” that joined us courtesy of a collision with the dwarf galaxy, Gaia–Enceladus.

The data comes from NASA's Transiting Exoplanet Survey Satellite (TESS) and thanks to a partnership with the European Space Agency's Gaia telescope our sky boffins confirm that v Indi's motion changed forever after a galactic collision.

Australian experts say the chances of an 11 billion year-old star being visible from Earth – albeit on a dark night down at the beach house - are low indeed.

"It’s amazing. Given that our eyes can only see 6000 of the 100 billion stars in our galaxy, the odds of one of them being this old were not high," says Professor Joss Bland-Hawthorn, director of the University of Sydney’s Institute for Astronomy.
The primary mission of TESS is to spot planets crossing in front of their parent star, but the spacecraft's instruments can be repurposed for many other types of investigations.

For this study, TESS used a technique called asteroseismology to track the oscillations of the star to estimate its age. Scientists then combined that work with observations from other ground and space observatories.

Of course, the Milky Way will get its own comeuppance when it is in turn devoured by our nearby, and slightly hungry neighbour Andromeda.

Andromeda is wearing out horses to consume our galactic home like a kookaburra on a baby goanna, heading our way at a decent clip of around 100km/sec, with an ETA of about 4.5 billion years.

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