The recent research using astronomical methods to study the fate of galaxies has revived interest in the possibility of a future Andromeda-Milky Way collision. While traditional understanding suggested an inevitable merger within 5 billion years, new simulations indicate that this outcome is far from certain. The Andromeda galaxy is more than 200,000 light-years across, nearly double the Milky Way’s width. Even now it sits some 2.5 million light-years from our home planet.
Despite this vast distance, Andromeda remains visible to the naked eye, particularly during spring and summer evenings in Australia, where it can be spotted just above the northern horizon. Andromeda looms as the Milky Way’s largest neighbor, and one of the biggest galaxies in our Local Group. This ‘Ringo’ group contains celebrity members such as the Triangulum Galaxy and the Large Magellanic Cloud.
The Simulations and Their Findings
A large team of astronomers ran detailed, large-scale cosmological simulations to model the complex interplay of gravitational forces between interacting galaxies through cosmic time. They performed over 100,000 different simulations to see how these galaxies could affect one another in different environments. Remarkably, in only 2 percent of these scenarios did Andromeda and the Milky Way come close enough—within 100,000 light-years—to merge.
For almost half of the simulations, the two galaxies sailed by each other without a collision. Because of this surprising result, investigators have had to reconsider what they previously thought they knew about the nature of their doomed reunion.
“It became clear that the merger is far from guaranteed.” – Dr. Wright
Nature doesn’t skimp on the complexity, and this research further underscores that multiple forces are very much at work in galactic dynamics. Dr. Wright continued to expand on this point, comparing the process to a game of snooker, where different and often random variables can dramatically impact results.
“It’s almost like you’re playing snooker, you’ve got 100 balls on the table, and you smash them and see where they’re going to go in 10 billion years,” – Dr. Wright
Dr. Wright explained that confounding elements such as dark matter add further complication to these simulations, significantly increasing the difficulty of making accurate predictions.
“The problem is the snooker balls are then soft and squishy, and they change shape, and there’s all these invisible balls on the table as well — which is dark matter.” – Dr. Wright
Implications of the Research
The policy ramifications of this research go well beyond research for research’s sake. By studying how galaxies interact and collide, astronomers can learn more about the evolution of the cosmos and what may lie in store for our own galaxy. Professor Harvey-Smith, who authored a book centered on the anticipated collision, described the study as “a really good paper to get people thinking.”
As he noted, it’s essential to constantly recalibrate our scientific understanding after acquiring new evidence.
“You constantly have to update science knowledge,” – Professor Harvey-Smith
These lessons further highlight the fact that astronomy remains a dynamic discipline where new ideas can and should!
“It’s great to see a fresh perspective on things that sometimes become embedded.” – Professor Harvey-Smith
The Future of Galactic Interactions
Our researchers are constantly reviewing new data and improving their models. Most of all, they are sure to make surprising discoveries about Andromeda and its companion galaxies. Galaxies thus interact through convoluted gravitational dynamics. Researchers haven’t stopped trying to peel back the layers to figure out how dark matter further complicates these interactions.
Dr. Wright echoed that right now, Andromeda and the Milky Way are pulling each other in with their gravity. They are not the only solo worlds on the galactic block.
“At the moment, the galaxies are being drawn together by the influence of their own gravity, but obviously these galaxies don’t exist in isolation.” – Dr. Wright
Combine with that other unseen forces that impact their trajectories too,” he said.
“There are other things tugging on them at the same time.” – Dr. Wright
As new telescopes and observational technologies enter service, researchers expect even more contradictions to established theory. Dr. Wright is confident that data from these new advances will “absolutely” shift prevailing understandings.
