Astronomers Sample the ‘DNA’ of 340,000 Stars

Like all the other stars in the universe, our sun was not born in isolation. The same clouds of dust and gas that gave rise to the sun and all the planets coalesced into other star systems that have since drifted away from us. Scientists from Australia have completed the most ambitious analysis yet of stellar “DNA” to track the origins of more than 340,000 stars. With this newly released data, astronomers may be able to find our sun’s siblings and learn about the evolution of the galaxy.

As we look out on the universe, scientists have spotted many regions of star formation. These places are dense with stars, but our little corner of the galaxy isn’t so dense. The sun was probably formed in a similar cluster with hundreds or thousands of other stars, though. The stars drift over time, but the sun’s celestial brothers may still be detectable. That’s the aim of the GALAH survey, which began in late 2013.

This project operates from the HERMES spectrograph at the Australian Astronomical Observatory’s (AAO), a 3.9-meter telescope in New South Wales. We can’t get close to these stars to take samples, but the light spectrum can tell us much. GALAH collects light from stars so that scientists can determine their chemical composition. If two stars formed from the same primordial material, they should have very similar compositions.

The project focuses on the ratio of almost two dozen elements, including oxygen, aluminum, and iron. This is what the team refers to as the “DNA” of the star. As long as a star hasn’t run through its hydrogen, it should not have started fusing heavier elements to alter the ratios. It takes roughly an hour to collect enough photons from a star to build a profile of its “DNA,” but the HERMES spectrograph can sample 360 stars simultaneously with the aid of fiber optics.

The GALAH project has made it first major public data release, but the work of tracking down the sun’s brethren is not yet done. For that, the Australian researchers are working with a team in Germany at the Max Planck Institute for Astronomy to develop a tool called The Cannon (named after American astronomer Annie Jump Cannon). The Cannon uses machine learning to identify patterns in the spectra and hopefully tell us which stars are related.

The release of GALAH data coincides with a separate publication of star maps from the European Gaia satellite. Together, the data from these projects can help us advance our understanding of the Milky Way including how stars form and move over time.