With the help of NASA's Hubble Space Telescope, scientists found that the orbital motion of two distant stars also provide clues to the stars' age.
NASA's Hubble Space Telescope helped scientists look back at the early days of the Milky Way and determine that the orbital motion of two distant population of stars provide proof that each of them formed at different times.
For the study, researchers compared recent Hubble observations from 2010 with 754 images belonging to eight years of data from the telescope's archive to determine the motions of 30,000 stars in the globular cluster 47 Tucanae. This globular cluster is 16,700 light-years away from the Earth in the southern constellation Tucana. By doing so, they were able to determine how fast the stars moved.
They found that two populations of stars in 47 Tucanae differed in age by less than 100 million years.
"When analyzing the motions of stars, the longer the time baseline for observations, the more accurately we can measure their motion," said Harvey Richer of the University of British Columbia in Vancouver in a press statement. "These data are so good, we can actually see the individual motions of the stars in the cluster. The data offer detailed evidence to help us understand how various stellar populations formed in such clusters."
The Milky Way has over 150 globular clusters with 47 Tucanae being the brightest. This globular cluster is approximately 10.5 billion years old.
During the study, the team also measured the brightness and temperature of the cluster and found two distinct populations of stars. The first one contained stars with chemicals and were redder, determining they were older and orbited in random circles. The second population had stars that moved in more elliptical orbits, were chemically richer and were blue in color, determining they were younger stars.
Though previous studies have established that globular clusters have multiple generation stars, this is the first research that has linked stellar dynamics to separate populations.
