Astronomers have found evidence suggesting that the Sun participated in a large-scale migration of similar stars from the Milky Way's inner regions about 4 to 6 billion years ago. This movement likely carried the solar system to a calmer part of the galaxy. The discovery comes from a detailed study of solar twins using data from the European Space Agency's Gaia satellite.
Astronomers have identified signs that the Sun joined a massive outward movement of Sun-like stars from the Milky Way's crowded center roughly 4 to 6 billion years ago. The Sun, which formed about 4.6 billion years ago, originated more than 10,000 light years closer to the galaxy's core than its current position.
A team led by Assistant Professors Daisuke Taniguchi of Tokyo Metropolitan University and Takuji Tsujimoto of the National Astronomical Observatory of Japan analyzed data from the Gaia satellite, which has measured around two billion stars. They created a catalog of 6,594 solar twins—stars with similar temperature, surface gravity, and chemical composition to the Sun. This sample is about 30 times larger than previous ones, allowing for precise age determinations after correcting for biases toward brighter stars.
The ages of these solar twins cluster between 4 and 6 billion years, matching the Sun's age. Many occupy similar distances from the galactic center, indicating a shared migration rather than coincidence. Normally, the galaxy's central bar creates a corotation barrier that hinders stars from moving outward, but the researchers suggest this structure was still forming during the migration period, enabling the escape.
This event provides insights into the Milky Way's evolution, including the development of its rotating bar. The inner galaxy's harsher conditions, with stronger radiation and frequent stellar interactions, contrast with the outer regions' stability. The migration positioned the solar system in a quieter area, potentially aiding the emergence of life on Earth.
The study utilized Gaia data and the Two Micron All Sky Survey, supported by grants from JSPS KAKENHI and the European Union's Horizon 2020 program.