Andromeda galaxy's star factory slows dramatically, astronomers find

The Andromeda galaxy, our closest large galactic neighbor, is experiencing a dramatic slowdown in its star formation, according to new analysis of Hubble Space Telescope data. Once a prolific 'star factory,' Andromeda's rate of creating new stars has been steadily declining over the past 500 million years, with a particularly sharp decrease in the last 40 million years.

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Each star is a fossil record of galaxy formation.

Researchers meticulously analyzed approximately 200 million stars across two-thirds of Andromeda's disk. By examining the age and color of stars in different regions, they traced the galaxy's star formation history. While Andromeda underwent a period of intense starburst activity about 2 billion years ago, likely due to a merger with another galaxy, its subsequent star production has waned considerably. It once formed stars equivalent to the mass of our Sun annually, but this rate has dropped to just 0.2 solar masses per year currently.

Scientists liken Andromeda's current state to a marathon runner catching their breath, suggesting it's entering a natural phase of decline rather than being starved of star-forming materials. The study, published in The Astrophysical Journal, points to a potential external influence on this slowdown. The research team highlights a significant decrease in star formation activity within a specific ring near the galaxy's core.

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Andromeda is like a runner who has finished a marathon and is catching their breath. It's not that it's running out of material to make new stars, but rather it has entered a natural period of decline.

This reduction is strongly linked to the close passage of Andromeda's satellite galaxy, M32, about 60 million years ago. The gravitational disturbance from M32 likely disrupted the gas distribution within Andromeda, triggering the observed decline in star birth. Future observations with the Nancy Grace Roman Space Telescope are expected to provide even more detailed insights into Andromeda's star formation history and its surrounding environment.

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The fact that star formation activity is significantly lower in the region near M32 suggests that the collision or close disturbance with M32 is the most likely culprit for the decrease in star formation.