Key takeaways:
- About 2 billion years ago, the Andromeda Galaxy absorbed a massive galaxy called M32p, which transformed into the compact, unusual satellite galaxy M32 that we see orbiting Andromeda today.
- This collision made Andromeda’s stellar halo dense with metal-rich, intermediate-age stars, and triggered a major burst of star formation, shaping Andromeda’s thickened disk.
- The merger theory suggests Andromeda’s current mass and structure resulted from a single large collision rather than multiple small mergers over time.
- M32 is unique among galaxies, as it’s both incredibly compact and contains many young stars, unlike typical old, elliptical galaxies.
- The study challenges previous ideas about galactic collisions, suggesting that spiral galaxy disks, like Andromeda’s, are more resilient to major impacts than previously thought.
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Around 2 billion years ago, Andromeda absorbed a massive galaxy, creating its unique satellite, M32.
A MASSIVE impact with a neighbor of Andromeda
Have you ever looked up at the stars and pondered what was going on up there? For centuries our galactic neighbor, the Andromeda Galaxy, has fueled our imagination. But new research sheds more light on its history in a manner that is simply unbelievable.
An international team of astronomers led by researchers at Yale University claims that Andromeda dined on its close companion, nicknamed M32p, 2 billion years ago, according to a study released in Nature Astronomy. Such an event shrank M32p into the small galaxy that we observe today. Why does this matter? It gives a suggestion of the evolution of galaxies over extremely long timescales.
Picture Andromeda as a galactic beast, tipping the scales with a mass seemingly at a trillion stars. And that mass exerts a strong force of gravity; it can tear galaxies apart if they are small enough. Once, M32p, itself a massive galaxy, was shorn of most of its gaseous and stellar mass. Its narrative is a touching tribute to the cosmic ballet of chaos, a pas de deux of galaxy mergers crashing together.
M32 is a total freak among galaxies. It’s an abnormal ball of stars with an eccentric collection of young stars, so not your typical elliptical galaxy, that has a very tight profile. Study co-author Eric Bell of the University of Michigan captured the sentiment with this quip: M32 is a weirdo. And you know what? He’s right. Figuring out how M32 was formed may reveal secrets about the wider universe itself.
M32 took on an incredible evolution, too. This compact type of galaxy has a surprisingly high density of young stars, which is non-typical for galactic classifications. This unusual feature sets it apart in the sights of galactic evolution scientists, and gives rise to questions of its formation history and ways to survive in space.
It seems that Andromeda did take quite a beating in the collision with M32p. The aftermath not only sculpted its stellar composition but likely induced a burst of star formation at the epoch of the merger. Bell envisions Andromeda then looking very different: an active churn of new stars against a tumbling swirl of cosmic debris.
This May Have Consequences For Galactic Evolution
What is greater than the in-the-know findings? This is more than just an Andromeda story. It serves as an X-ray of galaxy evolution on a grand scale. Their research provides new evidence that Andromeda’s spiral disk withstood the rough and tumble display, which is at odds with an early contention that galaxies’ components are delicate and cheap. Perhaps cosmic structures last longer than previously believed.
For the disk of Andromeda to have survived the collision is definitely something to think about in itself. Existing theories described dramatic apocalypse-like scenes following mergers. However, these galactic disks appear to have much more of a resiliency than we have previously realized. What other hidden mysteries are there in our universe?
As astronomers begin to peer further into interactions between galaxies, new questions arise. Mine are Andromeda and M32p, and what might be learned from them. The knowledge they have gained could shed light on what happens in the long run when galaxies collide, which is important in knowing how many stars our galaxy and millions of others will be in these lands of the universe.
In roughly four billion years, the Andromeda Galaxy is headed for a collision with the Milky Way. That prospect may be remote and imaginary at the moment. Still, as we take some time to go back through these occurrences from long ago, we can find an understanding of what might happen ahead. History is a valuable background for the future.
The stage of the cosmos is being played out right in front of us. With every astronomical discovery, we find ourselves even more rooted in the universe. Reminding us of our connection to a complex whole. Perhaps at least there is comfort in the fact that even galaxies collide and change, growing through disarray.
