Astronomers have long predicted that the Milky Way galaxy will collide with its largest neighbour, the Andromeda galaxy, in approximately 4.5 billion years. However, new research indicates that this event, referred to as “Milkomeda,” may not be as certain as previously thought.
Initially, the two galaxies, currently 2.5 million light-years apart and approaching each other at a speed of about 100 kilometres per second, seemed to be on a direct collision trajectory. Yet a recent study suggests the chances of an actual collision within the next 10 billion years may be only around 50%. Specifically, the probability of a merger occurring in the predicted timeframe of 4 to 5 billion years is now estimated to be just 2%.
This conclusion emerged from a study that incorporated the gravitational influences of over 100 smaller galaxies within the Local Group, including the Large Magellanic Cloud (LMC) and the Triangulum galaxy (M33). Researchers ran 100,000 simulations using fresh data from the Hubble and Gaia space telescopes, revealing that interactions among these galaxies might significantly alter the anticipated fates of the Milky Way and Andromeda.
In the event of a merger, both galaxies would lose their spiral structures, eventually merging into an elongated elliptical galaxy. Past studies suggested such mergers produce dramatic phenomena, like “cosmic fireworks,” as gas funneled into a central black hole causes an eruption of radiation. Study co-author Carlos Frenk noted that while a merger was once thought to be imminent, current findings indicate a less dire outcome might be probable.
Despite these positive projections, the authors of the study caution that predicting the ultimate fate of the Milky Way involves considerable uncertainty. In fact, the Milky Way has a higher likelihood of colliding with the LMC within the next 2 billion years, an event that could significantly transform our galaxy although it wouldn’t result in its destruction.
The interplay between galaxies, such as the LMC orbiting the Milky Way and M33 being a satellite of Andromeda, adds layers of complexity to these predictions. For instance, while the LMC contributes to pulling the Milky Way off its course towards Andromeda, M33’s gravitational effects also influence the trajectory of the Milky Way.
The study team accounted for various unknown factors influencing this cosmic dance, modelling numerous possible outcomes. Their work illustrates that while the Milky Way may not face imminent destruction from Andromeda, the long-term dynamics within the galaxy remain complex and unpredictable.
Ultimately, while the fate of the Milky Way’s merger with Andromeda remains uncertain, researchers assert that the end of our sun, which is expected to become a red giant in about 5 billion years, poses a far greater threat to Earth than a galactic collision.