Starry Treats

Christmas is three days away. But for many astronomers, Santa came early. In April, he brought a bagful of presents — new observations of more than a billion stars. Astronomers began sorting through those goodies right away. And they’ve already found some treats.

The observations were provided by Gaia, a European space telescope. It was launched five years ago. Its mission is to measure the positions, motions, and other details of more than a billion objects. A catalog of its observations was released in April.

The catalog includes the 3-D motions of about seven million stars. Astronomers can trace the paths of those stars, and look for patterns in the way stars are moving.

One team found about 20 stars that are moving so fast that they’ll escape from the Milky Way galaxy. But many of the stars are moving into the galaxy’s disk. That suggests they came from somewhere else, and are just passing through. The stars might have been born in other galaxies, but were kicked out by close encounters with black holes, or when companion stars exploded.

Another team found a region of the galaxy where many stars are moving like ripples on a pond. They may have been set on that course by an encounter with a small galaxy hundreds of millions of years ago. The galaxy came even closer later on, and was grabbed by the Milky Way, which is now “ingesting” the galaxy.

Astronomers will continue to study Gaia’s bag of goodies for many years to come.

Script by Damond Benningfield