The reporter learned from the National Astronomical Observatories of the Chinese Academy of Sciences that recently, researchers have used the precise seismological age of red giant stars to study the formation time of the thin disk of the Milky Way, and found that the earliest known thin disk star is about 9.5 billion years old. It provides an important observational basis for explaining the early formation and evolution history of the thin disk of the Milky Way.
Relevant research results were published in Monthly Notices of the Royal Astronomical Society (MNRAS).
Astronomers generally believe that the main characteristic structures of the Milky Way include the central bulge, the galactic disk and the galactic halo.
Among them, the galactic disk includes a thick disk and a thin disk, and the stars in the thick disk are formed before the stars in the thin disk, that is, the age of the thin disk is younger than that of the thick disk.
The formation of the thin disk is an important event in the Milky Way over the past 8 billion years or so.
What are the formation images of thin and thick disks?
When and where did the first thin-disk stars form?
These questions have been puzzling astronomers, and the key to solving these problems is to obtain accurate samples of the age of stars in the galactic disk.
Asteroseismology is considered to be one of the most accurate ways to obtain the age of stars at present.
Because the luminosity of the red giant is relatively high, it can be used as a tracer object to detect a farther distance from the galactic disk, so the red giant is one of the best probes for studying the galactic disk.
In the H-R diagram, people can see the relationship between the age of the red giant and the effective temperature. The systematic difference in the effective temperature of 50K can lead to a systematic difference of 10% in the age measurement, so it is quite difficult to obtain the accurate star age.
This scientific research achievement analyzed the influence of different temperature scales and models on the age measurement of red giant stars, and accurately determined the ages of 5306 red giant stars in the LAMOST-Kepler sample, with a typical error of 12%, which significantly improved the data based on large-sample asteroseismology. The stellar age accuracy of .
On this basis, researchers used chemical methods to distinguish between thin-disk stars and thick-disk stars, explored the age distribution of thin-disk stars in the Milky Way, and found that the age of the oldest thin-disk stars is about 9.5 billion years. Reflects ages estimated using different models of stellar evolution.
This is more consistent with the theoretical expectation of the previous "double inset" model of the galactic disk; during this time, the thick disk of the Milky Way is still forming stars, indicating that there is a common time window for the formation of stars in the thin disk and thick disk of the Milky Way.
In addition, the study also found that the metal abundance distribution and spatial distribution of the first batch of thin-disk stars are relatively extensive, which indicates that the inner disk and outer disk stars in the thin-disk stars may be formed at the same time.
This scientific research achievement is an important progress in the study of the age of the thin disk of the Milky Way from the perspective of asteroseismology, and it has laid a foundation for further exploration of the early formation and evolution history of the Milky Way.
(CCTV news client headquarter CCTV reporter Shuai Junquan Chu Erjia)