Astronomers created a 3D atlas, mapping more than a million widely separated binary stars using new data from the Gaia space observatory.
Utilizing Gaia data released last December, Kareem El-Badry, a campus PhD student in the department of astronomy, constructed an extensive catalog of binary stars in order to better understand star formation and create stellar models. The atlas also includes 16,000 binary stars consisting of main sequence stars — which fuse hydrogen atoms to form helium — and white dwarf stars which have lost most of their mass, according to the astronomers’ manuscript.
“Binary stars are two stars that form out of the same gas cloud,” El-Badry said. “All stars are formed from gas clouds but sometimes the cloud fragments as it forms so you have two stars with the same age and the same composition.”
El-Badry collaborated with Hans-Walter Rix, a director at the Max Planck Institute for Astronomy, and Boston University graduate student Tyler Heintz, who worked specifically with white dwarf data. The team located possible binaries by looking for stars that have the same distance, similar planes of motion and are close in proximity, according to El-Badry.
The team then filtered out stars that may have been aligned by chance by analyzing nearby clusters of stars and the distances between them. El-Badry noted that “to be confident” two stars are in a binary system, they would need to be much closer than any other random pair of stars nearby.
Astronomers can use this atlas to measure the ages of main sequence stars and understand star formation, El-Badry said. Main sequence stars are still living, and their properties do not change for billions of years, making it hard to measure their age. White dwarfs, however, get cooler over time, making it easier to calculate their age.
“If you have a white dwarf and a main sequence star in a binary, you can measure the age of the white dwarf and you know the main sequence star has the same age,” El-Badry said. “It’s one of few ways to measure ages of main sequence stars.”
The catalog of binary stars can also be used to create better stellar models, El-Badry added. Since the two stars in a binary have the same age and distance, astronomers can cross-check the distances given by Gaia and compute any errors.
The unprecedented size of the atlas was due to the “amazing” Gaia mission, El-Badry said. While astronomers have compared stars for hundreds of years, well-measured distances from the past few years have made locating binaries possible.
“The data is orders of magnitude more precise than studies that came before it,” El-Badry said. “I download the catalog and do statistical analysis with it, but it’s really the work of hundreds of scientists that make this work possible.”