HUBBLE DATA SHOWS ANDROMEDA STAR FORMATION IN STEEP DECLINE

A study using data from NASA's Hubble Space Telescope has found that star formation in the Andromeda galaxy has declined over the past 500 million years, with a steeper drop recorded in the last 40 million years. The research, published on Monday in The Astrophysical Journal, analysed approximately 200 million individual stars across Andromeda to build a detailed picture of the galaxy's formation history. The Andromeda galaxy, located about 2.5 million light-years from Earth, is comparable in size to the Milky Way and visible to the naked eye from areas with dark skies.

Researchers combined data from two Hubble surveys—the Panchromatic Hubble Andromeda Treasury and the Panchromatic Hubble Andromeda Southern Treasury—which together mapped two-thirds of Andromeda's disk in high-resolution detail. The team divided images into thousands of sections, each spanning 300 light-years, to determine star formation history in each area. Previous research has established that Andromeda experienced a dramatic burst of star formation approximately 2 billion years ago, likely caused by a past interaction or merger with another galaxy. Astronomers distinguish recent from older star formation by examining stellar colour: massive, short-lived stars appear blue, whilst less massive, longer-lived stars appear red.

Ben Williams, astronomer at the University of Washington and co-author of the study, stated that individual stars serve as "the fossil record of the galaxy's formation" and that "Hubble is the only telescope that can give you high enough spatial resolution over a large enough area to be able to do that in Andromeda." The findings offer astronomers insight into the long-term evolution of galaxies similar to our own Milky Way. Star formation rates are measured by the mass of gas and dust converted into stars per year.