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Studies show that the band of stars at the center of the Milky Way appears remarkably young and that future models of galaxy evolution will need to consider why this band evolved later.
The ages and locations of the metal-rich stars indicate that the band finished forming just a few billion years ago, and the study states that the band we see today is a stable feature about 10 billion years younger than the entire galaxy.
The study suggests that metal-rich stars are “fossil records of ancient stars that tell the story of our home galaxy,” and the study notes that the central band of the Milky Way has dispersed some of these stars throughout the galaxy.
Using data from the European Space Agency’s Gaia space telescope, Nepal and colleagues reconstructed the evolution of the Milky Way band by examining its effect on the distribution of metal-rich stars. They inferred the history of the band, just as you might deduce the positions of players in a baseball game by watching the movement of the balls they hit, even if you can’t see the home plate.
By tracking the ages of the metal-rich stars, researchers were able to pinpoint a spike in star formation in the central part of the galaxy about 3 billion years ago. This decline appears to indicate the end of the Milky Way band’s formation phase in the Milky Way, according to the researchers’ report. After this spike, they say the inflow of new material into the band dropped significantly. This suggests that the band we see today is a stable feature about 10 billion years younger than the entire galaxy.
Christina Kiabini, an astronomer at the Leibniz Institute for Astrophysics in Potsdam, Germany, states that the new signals regarding metal-rich stars “are like the tip of the iceberg” of data coming from the Gaia telescope. If the new estimates for the age of the band are confirmed, future models of galaxy evolution will have to explain why the band evolved later.
The study suggests that it has broader implications than merely correcting the timeline of our galaxy, and Ortwin Gerhard, an astronomer at the Max Planck Institute for Astrophysics in Garching, Germany, who did not participate in the research, says that “the potential for detailed observations of the stars’ motions and their chemical balances in the Milky Way, especially based on data from the Gaia satellite,” means we can “expect to learn more about the evolution of bars [in other galaxies] in general by studying the band in the Milky Way.”
References:
S. Nepal et al. Insights from super-metal-rich stars: Is the Milky Way bar young? arXiv:2311.16993. Submitted November 28, 2023.
Source: Science News
Source: https://www.sciencenews.org/article/milky-way-bar-young-metal-stars
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