Hubble’s Deepest Look at Andromeda Reveals a Galactic Mystery Millions of Years in the Making – Indian Defence Review

Hubble’s latest survey of Andromeda reveals a chaotic past, a swarm of satellite galaxies, and a cosmic mystery that challenges everything we know about galaxy evolution.The Andromeda Galaxy, located 2.5 million light-years away, is one of the most studied objects in the night sky. While it appears as a hazy, spindle-shaped glow to the naked eye, it harbors a vast and complex system of satellite galaxies. Now, NASA’s Hubble Space Telescope has provided the first three-dimensional mapping of this system, revealing an asymmetrical structure shaped by past cosmic upheavals. Unlike the Milky Way’s relatively stable satellite population, Andromeda’s companions suggest a history of violent interactions—possibly a major collision billions of years ago.With over 1,000 Hubble orbits dedicated to the survey, astronomers are reconstructing Andromeda’s evolutionary past, uncovering clues about how galaxies form and evolve over cosmic time. Their findings, recently published in The Astrophysical Journal, reveal a dynamic and complex satellite system—one that challenges long-held assumptions about galactic ecosystems and suggests a more tumultuous history for Andromeda than previously thought.At the heart of this groundbreaking study is a simple yet profound question: Why is Andromeda’s satellite system so different from our own?The Milky Way, like Andromeda, has a population of satellite galaxies, but they appear to follow a different evolutionary trajectory. Many of the Milky Way’s smaller companions seem to have exhausted their ability to form new stars long ago. In contrast, Andromeda’s dwarf galaxies have continued forming stars much later than expected, challenging established theories of galaxy formation.“We see that the duration for which the satellites can continue forming new stars really depends on how massive they are and on how close they are to the Andromeda galaxy,” said lead author Alessandro Savino of the University of California at Berkeley. “It is a clear indication of how small-galaxy growth is disturbed by the influence of a massive galaxy like Andromeda.”This discovery suggests that Andromeda’s immense gravitational pull—and possibly the lingering effects of past mergers—has disrupted and reshaped its satellite population in ways that haven’t been observed in the Milky Way. Unlike our home galaxy, where many small galaxies stopped forming stars billions of years ago, Andromeda’s satellites appear to have been supplied with gas for much longer periods, allowing star formation to continue at a slow but steady pace.One of the most striking findings from the Hubble survey is the unusual structure of Andromeda’s satellite system. Instead of being scattered randomly, nearly half of its satellite galaxies appear confined to a single plane and orbiting in the same direction—a highly unexpected feature that has left astronomers searching for explanations.“Everything scattered in the Andromeda system is very asymmetric and perturbed. It does appear that something significant happened not too long ago,” said principal investigator Daniel Weisz of the University of California at Berkeley.This asymmetry suggests that Andromeda’s past was anything but peaceful. A major merger—perhaps with another large galaxy—may have disrupted its satellite system, causing it to form in an ordered yet chaotic configuration. The evidence for this event can be seen in Andromeda’s most prominent satellite galaxy, M32, which scientists believe could be the stripped core of a larger galaxy that merged with Andromeda billions of years ago.Such an event would have dramatically reshaped Andromeda’s satellite system, flinging some galaxies into new orbits while triggering bursts of star formation in others. If true, this would mean that Andromeda’s current state is a cosmic snapshot of a galaxy in transition, still settling from a collision that reshaped its structure and behavior.For decades, astronomers have relied on the Milky Way as a model for understanding galaxy formation. But this new study of Andromeda challenges the idea that all large galaxies evolve in the same way.“There’s always a tendency to use what we understand in our own galaxy to extrapolate more generally to the other galaxies in the universe,” said Weisz. “There’s always been concerns about whether what we are learning in the Milky Way applies more broadly to other galaxies. Or is there more diversity among external galaxies? Do they have similar properties?”This study confirms that low-mass galaxies in other ecosystems have followed different evolutionary paths than those in the Milky Way, raising new questions about how universal our current models of galaxy formation truly are.One of the most perplexing aspects of Andromeda’s satellite galaxies is that they didn’t stop forming stars when theory predicted they should. Instead, many of these smaller galaxies seem to have had access to reservoirs of gas for much longer periods, fueling continued star formation at a slow but steady rate. This phenomenon doesn’t appear in computer simulations, leaving scientists with a puzzle that defies expectations.“Star formation really continued to much later times, which is not at all what you would expect for these dwarf galaxies,” said Savino. “This doesn’t appear in computer simulations. No one knows what to make of that so far.”Comment Save my name, email, and website in this browser for the next time I comment.

© 2024 | Indian Defence Review  | All rights reserved

Source: https://indiandefencereview.com/hubbles-andromeda-reveals-galactic-mystery/