Andromeda's Star Formation Slows Over 500 Million Years

A Hubble-based study of Andromeda (M31) using PHAT/PHAST surveys finds its star formation has declined for about 500 million years, with a sharper drop in the last 40 million, especially on the side near the satellite galaxy M32. While not proven, M32 is the leading candidate for helping slow star birth. The work highlights Andromeda as a Milky Way analog and points to future Roman Space Telescope observations that could map the entire disk and add hundreds of millions of stars to the record.