Letter to the Editor

Solar twins in Gaia DR3 GSP-Spec

II. Age distribution and its implications for the Sun’s migration

¹ National Astronomical Observatory of Japan 2-21-1 Osawa Mitaka Tokyo 181-8588, Japan
² Department of Physics, Tokyo Metropolitan University 1-1 Minami-Osawa Hachioji Tokyo 192-0397, Japan
³ Université Côte d’Azur, Observatoire de la Côte d’Azur, CNRS, Laboratoire Lagrange, Bd de l’Observatoire CS 34229 06304 Nice cedex 4, France

^★ Corresponding authors: This email address is being protected from spambots. You need JavaScript enabled to view it. ; This email address is being protected from spambots. You need JavaScript enabled to view it.

Received: 10 January 2026
Accepted: 9 February 2026

Abstract

Solar twins are among the most powerful tracers of Galactic disk evolution owing to their unique property of sharing nearly solar metallicities ([Fe/H] ≈ 0) while spanning a wide range of ages. To grasp solar twins as relics of Galaxy evolution, individual twins must be tagged with ages. A sufficiently large and well-characterized stellar sample then allows us to construct an age distribution that encodes the star formation history beyond our local region, modulated by the efficiency of radial migration of stars. Based on our catalog of 6594 high-quality local (≲300 pc) solar twins from the Gaia Data Release 3 spectroscopic (GSP-Spec) catalog, we derived their age distribution after carefully deconvolving the selection function. We find two distinct features: a narrow peak around ∼2 Gyr and a broad bump extending over ∼4 − 6 Gyr. First, we argue that the former corresponds to a relatively recent burst of star formation that occurred in the disk, including at least a local region within a few kiloparsecs of the Sun, which is in good agreement with previous results deduced from independent works. On the other hand, the older bump, closely associated with the Sun’s birth epoch, is intriguing since this finding challenges the predicted presence of a corotation barrier built by the Galactic bar, which is thought to prevent stars born inside R_GC ≈ 6 kpc from reaching the solar neighborhood. We propose that the large number of local twins with ages between 4 and 6 Gyr provides compelling evidence that the Sun’s long-distance (≥3 kpc) migration is shared by many inner disk stars. This, in turn, suggests a possible link with the epoch of bar formation, which may have triggered enhanced star formation in the inner disk and induced efficient radial migration.