60-Second Science

Some Milky Way Stars Are Survivors of Older Galaxies

Computer simulations show that stars of the Milky Way's halo originated in older galaxies torn apart by collisions. Cynthia Graber reports

It’s a plotline worthy of an action film—galaxies, violently torn apart, smashing into one another, leaving remnants of themselves behind billions of years later. That’s the scene that accounts for some of the oldest stars in our own Milky Way galaxy, according to work published in the journal Monthly Notices of the Royal Astronomical Society. [Andrew Cooper et al.,]

Researchers ran a huge computer simulation of the evolution of the universe starting shortly after the big bang, more than 13 billion years ago. It’s the most detailed model ever produced, and allowed a close examination of the make-up of the Milky Way’s stellar halo. The stellar halo is debris that surrounds our familiar white swirl of stars. The halo is much larger and much older than the Milky Way itself.

And the simulations show that the ancient stars in the halo were formed from young, small galaxies that collided and left behind fragments of themselves, as opposed to those stars actually being born in the Milky Way when it started forming 10 billion years ago. The researchers say the scene depicts the dramatic—and violent—clashes that were taking place long, long ago, in a galaxy not very far away.

—Cynthia Graber

[The above text is an exact transcript of this podcast.]

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