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The stars in our galaxy can change orbits over time. Through “close encounters” with other stars, they can find themselves in very different regions of the galaxy than their region of origin. Now new research finds that about a third of stars drift to new orbits in their lifetime.
The results come from the SDSS Apache Point Observatory Galactic Evolution Explorer (APOGEE), which looked at the spectra of more than 100,000 stars over a 4 year period. From this spectra the team could determine the what elements each star has in its atmosphere. By calculating the amount of each element in a star (known as the star’s metallicity) the team could identify which stars formed in the same region, and the distance from galactic center where different stars formed. What the team found was that about 30% of the stars measured were in regions very different from their region of birth. Since the team focus on red giant stars, which are stars at the end of their lives, this means about a third of stars will shift to dramatically new orbits in the galaxy over the course of their lifetime.
Paper: Michael R. Hayden et al. Chemical Cartography with APOGEE: Metallicity Distribution Functions and the Chemical Structure of the Milky Way Disk. ApJ 808 132. doi:10.1088/0004-637X/808/2/132 (2015)