A study using NASA's Hubble Space Telescope shows star formation in the nearby Andromeda galaxy has declined for 500 million years, with a steep drop in the last 40 million years.
Image credit: NASA ScienceLocated 2.5 million light-years away, Andromeda is a spiral galaxy comparable to the Milky Way. Its proximity allows astronomers to examine individual stars to understand past stellar growth.
Image credit: NASA ScienceResearchers combined two Panchromatic Hubble Andromeda Treasury surveys. By measuring about 200 million individual stars across the disk, the team built a comprehensive timeline of Andromeda's past activity.
Image credit: NASA ScienceYounger, massive stars appear bluer, whereas older, lower-mass stars look redder. Scientists divided images into 300-light-year squares to map variations in star-forming activity over time.
Image credit: NASA ScienceStar formation dropped from one solar mass per year 500 million years ago to half that 40 million years ago. Today, the rate is just one-fifth of a solar mass annually.
Image credit: NASA ScienceRecent star formation is concentrated in a ring 32,000 light-years from the core. Decreasing activity inside this structural ring accounts for much of Andromeda's overall slowdown.
Image credit: NASA ScienceScientists checked if nearby satellite galaxy M32 triggered the reduction. A slowdown near M32 starting 60 million years ago suggests a potential past encounter between the two galaxies.
Image credit: NASA ScienceFuture wide-field views from NASA’s upcoming Nancy Grace Roman Space Telescope will cover 100 times more area than Hubble, mapping Andromeda’s entire disk and outer halo.
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