The astronomical world is abuzz over a new map of the Milky Way that reveals some surprising facts about stars: a full third of them are far away from where they were formed.

Astronomers using the Sloan Digital Sky Survey-III (SDSS), which enables astronomers to use spectroscopically linked chemical elements in the star to figure out where they began based on regions in the galaxy that are known to have a lot of those elements, were able to find that about 30 percent of the stars have been flying chaotically through the galaxy and are now far from where they started, according to a Discovery News report.

About 70,000 stars were measured in the galaxy for the study, and the used the SDSS infrared spectrograph to do most of the work, said Donald Schneider of Penn State University — a coauthor of the study — according to the report.

He called it “galactic archaeology,” in that much like archaeologists here on Earth use certain clues from artifacts to measure their age, astronomers are doing the same thing — take data on their locations, motions, and their chemical compositions to figure out how they formed and what their history is.

During the life cycle of a star, heavier elements are often found in the atmospheres of a given progressive stellar population, and by measuring the spectroscopic signature of a given star, scientists can tap into the chemical fingerprint to determine when and where they formed.

The finding shows that the chemical makeup of the galaxy is changing constantly, and that as stars die, they leace behind heavier elements that go back into the gas and lead to the formation of more stars.

And it’s not necessary in one direction that they migrate: some go inward, some go outward, and it appears to be due to irregularities in the distribution of mass in the Milky Way’s disk, as you can see with the spiral arms.