Our sun and a host of sun-like “solar twins” may have migrated away from the core of the Milky Way galaxy together, potentially making the solar system more hospitable to life as we know it, new research finds.
Around the Milky Way are solar twins, stars that physically appear very similar to the sun. By analyzing solar twins, astronomers hope they can learn more about the history of the sun.
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“We found many more solar twins with ages similar to the sun than I had expected,” researcher Daisuke Taniguchi, an astronomer at Tokyo Metropolitan University, told Space.com.
By analyzing the sizes, temperatures and compositions of these nearby solar twins, Taniguchi, Takuji Tsujimoto at the National Astronomical Observatory of Japan and their colleagues were able to estimate the stars’ ages. Looking at the range of ages, they noticed a broad peak for 1,551 stars about four billion to six billion years old. (This population includes our sun, which is about 4.6 billion years old.)
The discovery that the sun and many of these solar twins are of similar ages and located about the same distance from the center of the galaxy suggests that the sun is not at its current position by accident. Previous research suggested that, based on the sun’s “metallicity” — its levels of elements heavier than hydrogen and helium — it was born more than 10,000 light-years closer to the galaxy’s inner regions, which are higher in metals than the part of the galaxy in which the sun now resides.
The new results suggest the sun may be a part of a larger population of stars that migrated outward from the galactic core at about the same time — four billion to six billion years ago.
“We are learning about the sun’s past trajectory indirectly by studying other, similar stars,” Taniguchi said.
This discovery sheds light not only on the nature of our solar system, but the evolution of the galaxy itself. At the center of the Milky Way is a giant rotating bar-like structure that would now make it difficult for such a mass migration of stars to occur. However, these new findings reveal details about when this “co-rotation bar” formed. Indeed, the birth of this enormous sweeping bar may have initially concentrated gas to help trigger star formation and then propel stars outward, the researchers suggested.
These new findings might also shed light on what conditions may have helped life on Earth to evolve, the researchers said.
“The inner regions of the Milky Way are thought to be more hostile environments for life, with energetic events such as supernova explosions occurring more frequently,” Taniguchi said. If the sun migrated outward relatively soon after its birth, “the solar system may have spent most of its history in the quieter outer disk. In other words, the sun may not have arrived in a life-friendly environment purely by chance, but rather as a consequence of the formation of the galactic bar.”
The scientists aim to expand their work to cover a larger release of data from Gaia planned for December. They also plan to look more closely at the compositions of these solar twins, which “may help identify stars that were born in the same place and at the same time as the sun — that is, true twins,” Taniguchi said.
The scientists detailed their findings March 12 in two studies in the journal Astronomy & Astrophysics.
