The Milky Means’s thick disk is 2 billion years older than astronomers beforehand thought and sure shaped barely 800 million years after the Large Bang, a brand new research based mostly on an uncommon kind of star discovered.
Our galaxy could be cut up into two main components: the skinny disk, which holds the photo voltaic system and most of what we acknowledge because the Milky Means; and the a lot sparser, bigger and older thick disk. To reconstruct the historical past of those parts, a workforce of astronomers from the Max-Planck Institute for Astronomy in Heidelberg, Germany, checked out a inhabitants of stars within the Milky Means often known as sub-giants.
Sub-giants are stars captured within the temporary (in cosmic phrases) interval between their common stellar life and the crimson large section, through which they develop far past their authentic envelope.
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Nuclear fusion on the cores of those stars has simply stopped, however the stars have not bloomed out into crimson giants but. For the reason that sub-giant section in a star’s life solely lasts a couple of million years, astronomers can pinpoint the age of those stars by evaluating their chemical composition with pc fashions of stellar evolution.
Within the new research, the scientists decided the ages of 250,000 sub-giants within the Milky Means utilizing knowledge from the European Area Company’s (ESA) Gaia mission and China’s Giant Sky Space Multi-Object Fiber Spectroscopic Telescope (LAMOST).
The info revealed that many of the star formation within the Milky Means’s historical past occurred in two distinct waves. The primary wave, related to the thick disk, began solely 800 million years after the Large Bang, some 13 billion years in the past, however accelerated 2 billion years later when the nascent Milky Means collided with one other galaxy, which astronomers name Gaia-Sausage-Enceladus, ESA mentioned in an announcement.
This collision could have crammed the thick disk in addition to the stellar halo surrounding the complete galaxy with stars. It, nevertheless, took one other 5 to six billions of years for the skinny disk to emerge within the subsequent huge wave of star formation, which included the solar.
“For the reason that discovery of the traditional merger with Gaia-Sausage-Enceladus, in 2018, astronomers have suspected that the Milky Means was already there…however we didn’t have a transparent image of what that Milky Means seemed like,” Maosheng Xiang, an astronomer on the Max Planck Institute for Astronomy and one of many paper’s authors, mentioned in an announcement printed by the European Area Company.
The research (opens in new tab) was printed within the journal Nature on March 23.
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