NEWS NOTES
Baby stars found in ancient part of our Galaxy
ASTRONOMERS HAVE DISCOVERED a collection of young stars in a surprising location: the Milky Way’s halo.
Adrian Price-Whelan (Flatiron Institute) discovered the stars while digging through data collected by the European Gaia mission. The newfound stars are 117 million years old and move together as a set. They’re similar to open clusters like the Pleiades in both age and mass. But at 94,000 light-years away, the new stars are 200 times farther away than the Seven Sisters. They’re also more spread out, spanning some 2,500 light-years, and are not gravitationally bound.
By rights, the stars shouldn’t be out there at all. There’s not much star-making gas in the Milky Way’s halo, as most of the gas is too hot and diffuse to collapse into new suns. What little cool gas there is resides in the Magellanic Stream, a long gaseous ribbon that travels with the Large and Small Magellanic Clouds through our galaxy’s outer regions.
And the new stars appear to be sailing right in front of that ribbon of gas.
To investigate the stars’ properties, David Nidever (Montana State University), Price-Whelan and colleagues took spectra of 28 of the brightest stars in the group. The measurements showed that the stars have a fairly pristine composition. Both their composition and velocities match that of the leading arm of the Magellanic Stream. In two papers in the Astrophysical Journal, the team concludes that these stars likely formed from the gas at the head of the Magellanic Stream.
Murmurs of excitement from fellow astronomers met Price-Whelan and Nidever when they reported these results at a meeting of the American Astronomical Society in Honolulu. Observers have been looking for
