Cosmic engines across Andromeda sputtered: Microscopic neighbor triggers long fade

Astronomers using data from the Hubble Space Telescope have identified a significant decline in star formation rates within the Andromeda galaxy over the last 40 million years. The research suggests that a miniature satellite galaxy, M32, may be responsible for slowing these evolutionary processes.

While it was previously known that Andromeda experienced a massive burst of star formation approximately 2 billion years ago—likely triggered by contact with another cosmic object—the subsequent decline in activity had not been detailed chronologically. The current study provides the data necessary to trace this fading process.

Mapping 200 Million Stars

To analyze the galaxy, located 2.5 million light-years away, Hubble observed stars brighter than the Sun across two-thirds of Andromeda's disk. Researchers collected data on 200 million stars by dividing the region into a grid of squares, each with a side of 300 light-years.

The team determined the history of each sector based on stellar color: bright blue stars indicate recent active formation, while a dominance of small red dwarfs suggests an older region. This mapping revealed that Andromeda's star production has dropped from one solar mass per year 500 million years ago to just one-fifth of that rate today.

The Influence of M32

The decline in star formation is not uniform; one side of Andromeda is "cooling" faster than the other. This specific area coincides with the location of M32, a tiny satellite galaxy positioned only 16,000 light-years from its neighbor. Astronomers believe M32 may be the remnant of a spiral galaxy that lost its arms during a collision with Andromeda.

Although the impact of M32 is not yet a proven fact, current data shows a direct correlation between the proximity of the dwarf galaxy and the reduced birth rate of stars. Researchers hypothesize that gravitational disturbances from M32 acted as the primary brake on Andromeda's evolution.

Next Steps in Observation

To move these hypotheses into the realm of strict evidence, astronomers plan to use the Nancy Grace Roman Space Telescope. This instrument will allow for larger-scale measurements covering a broader area than Hubble could achieve.

Pavel Gromov, an astronomer, noted that modern observation technologies now enable the study of the dynamics of processes lasting millions of years, representing a significant advancement in cosmic understanding over the past few decades.

Questions about Andromeda's Evolution

What does a drop in star formation signify?

It indicates that the galaxy is depleting its reserves of gas and dust necessary to create new stars, resulting in decreased activity.

Is M32 part of the Andromeda galaxy?

No, it is a separate satellite galaxy, though its proximity makes it highly susceptible to Andromeda's gravity.

Source: This article was adapted from an original Russian-language publication by Pravda.Ru.