Free Astronomy Magazine May-June 2026

47 MAY-JUNE 2026 ASTRO PUBLISHING T he mass stellar migration model proposed by the research. BYA = billion years ago. [NAOJ] servatory of Japan undertook an unprecedentedly large study of solar “twins,” stars which have very similar temperature, surface gravity, and composition to our Sun. They used data taken by the European Space Agency’s Gaia satellite mis- sion, a daunting trove of observa- tions covering two billion stars and other objects. They created a cata- logue of 6,594 stellar “twins,” a col- lection around 30 times larger than previous surveys. From this immense list, they were able to obtain the most accurate picture to date of the ages of these stars, carefully correct- ing for the selection bias of stars which are easier to see. Looking at the distribution of ages, they noticed a broad peak for stars around 4 to 6 billion years old: this includes our Sun, and is evidence for similar stars of similar age, posi- tioned around the same distance from the center of the Galaxy. This means that our Sun is not at its cur- rent position by accident, but as part of a much larger stellar migra- tion. This discovery sheds light not only on the nature of our Solar System, but also the evolution of the Galaxy itself. The corotation barrier created by the bar structure at the galactic center would not allow for such a mass egress. However, the story changes if the bar was still being formed at the time. The ages of our stellar “twins” reveal not only when the mass escape occurred, but also the time range over which the bar was formed. The center of the Galaxy is a far less hospitable envi- ronment for the evolution of life than the outer regions. The team’s findings thus illuminate a key factor in how our Solar System, and in turn our planet, found itself in a region of the Galaxy where organisms could develop and evolve. In the future the team hopes to use precise observations of the stars sim- ilar in age to the Sun to look for stars born near the same time and place as the Sun to deter- mine the point of ori- gin and travel route of the mass migra- tion. It is expected that the Japanese JASMINE astrometry satellite mission being developed by the Na- tional Astronomical Observatory of Japan will contribute to this research. T he relationship between color and luminosity for various types of stars. Solar twins refer to stars with colors and luminosities similar to the Sun (stars within the red trapezoid). [D. Taniguchi & T. Tsujimoto] !