It has been centuries since astronomers first discovered the Andromeda galaxy, and nearly a century has passed since the scientific community recognized that this celestial body is moving closer to us. In other words, the Andromeda galaxy and our own, the Milky Way, are on a collision course that promises to be spectacular. But is this truly the case?
A recent study conducted by researchers at the University of Helsinki challenges this assumption. They examined several critical factors, such as the gravitational influence of other galaxies, and concluded that the likelihood of this galactic merger occurring within the next 10 billion years is only 50%.
Have astronomers been mistaken for a long time? To provide clarity, scientists in Helsinki have approached what is known as the “four-body” problem. This problem involves significant uncertainty, which helps to explain the remaining 50% chance that this interstellar event might take place.
The “four-body” problem, more formally known as the N-body problem, is defined as “a problem in celestial mechanics consisting of determining the trajectories of a set of N bodies attracting each other,” as per its Wikipedia entry.
The key point to grasp is that this is an especially complex issue requiring extensive calculations, as well as a comprehensive understanding of the various influential factors.
The authors of the new study suggest that analyzing the Andromeda and Milky Way galaxies in isolation fails to account for the other galaxies within what we refer to as the “Local Group.” This Local Group comprises around 100 smaller galaxies, each with its own orientation, distance from one another, and velocity.
The largest of these neighboring galaxies is the Triangulum Galaxy, located 2.7 million light-years away from us and containing approximately 40 billion stars. This represents about 40% of the estimated 100 billion stars in the Milky Way but only 4% of the estimated 1 trillion stars in Andromeda. Nonetheless, this relatively “small” number of stars possesses its own gravitational influence, complicating the “simpler” dynamics between Andromeda and the Milky Way.
The researchers also emphasize the significance of the Large Magellanic Cloud, which is the second or third closest galaxy to ours, situated just 163,000 light-years away. With its 20 billion stars, it also exerts a gravitational influence in our galactic vicinity.
The study’s authors have factored in the gravitational impact of these two additional galaxies while calculating the trajectories of the Milky Way and Andromeda over the next billion years.
They propose that the intricate movements of these cosmic giants could result in a situation where the two galaxies do not ultimately merge. However, another element that must be considered is uncertainty.
To navigate this challenge, researchers rely on estimates instead of fixed numbers. Accordingly, the authors assess that there is a 50% chance of a collision and subsequent merger between the two galaxies.
However, the researchers warn that numerous factors contribute to this considerable uncertainty, which includes the influence of other galaxies in the Local Group.
In the end, they conclude that time will eventually unveil the truth about this mystery, although we are discussing incredibly long time frames. If such a collision were to occur, it would likely happen long after our sun has shone its last rays. Humanity will either perish alongside our star—unless it disappears long before that—or it will have developed the ability to traverse between solar systems, thereby gaining access to an almost limitless abundance of resources.
Subscribe to our sprawling newsletter
Support us for the price of a coffee
The Future of the Andromeda and Milky Way Collision: 50% Probability of Merge
It’s been centuries since astronomers discovered the existence of the Andromeda galaxy; it’s also been about a century since the scientific community noticed that this celestial object was approaching us. In other words, the two galaxies, Andromeda and our own, the Milky Way, will collide in a spectacular way. But is this really true?
Challenging the Collision Hypothesis
A new study by researchers at the University of Helsinki challenges the long-standing belief regarding the impending collision between the Andromeda Galaxy and the Milky Way. By examining several important factors, including the gravitational influence of other nearby galaxies, researchers found that the chances of a galactic merge are only 50% over the next 10 billion years.
The “Four-Body” Problem Explained
To investigate this issue in-depth, scientists have tackled a complex problem known as the “four-body” problem. This problem, in celestial mechanics, involves determining the trajectories of a set of N bodies attracting each other, adding layers of complexity to predictions about galactic interactions.
Understanding the Complexity
The “four-body” problem requires intricate calculations and a comprehensive understanding of multiple celestial factors. Historically, astronomers have focused singularly on the behaviour of Andromeda and the Milky Way, largely ignoring the gravitational effects of the “Local Group”—a collection of about 100 small galaxies in proximity.
Influential Neighbors: The Local Group
The largest galaxy in this Local Group is the Triangulum Galaxy, located 2.7 million light-years from Earth. It boasts approximately 40 billion stars—about 40% of the Milky Way’s estimated 100 billion stars but only 4% of the Andromeda’s estimated 1 trillion stars.
The Gravitational Impact of Other Galaxies
Even these seemingly “small” galaxies exert a significant gravitational pull that complicates the dynamics between Andromeda and the Milky Way:
- Triangulum Galaxy: 2.7 million light-years away; 40 billion stars
- Large Magellanic Cloud: about 163,000 light-years away; 20 billion stars
By incorporating the gravitational effects of these two galaxies into their trajectory calculations, the researchers unveiled new dynamics that could prevent a merger.
| Galaxy | Distance from Milky Way (light-years) | Estimated Number of Stars |
|---|---|---|
| Triangulum Galaxy | 2.7 million | 40 Billion |
| Large Magellanic Cloud | 163,000 | 20 Billion |
| Andromeda Galaxy | 2.537 million | 1 Trillion |
| Milky Way | – | 100 Billion |
Predicting the Collision: 50% Probability
According to the studies conducted by researchers, it is essential to understand the significant uncertainties that affect their predictions. They quantify the likelihood of a collision between the galaxies as a 50% probability, stressing that this estimation is heavily influenced by various gravitational factors from nearby galaxies.
Factors Contributing to Uncertainty
Several key factors contribute to this large uncertainty, including:
- The complex gravitational interactions within the Local Group
- The different orientations and velocities of neighboring galaxies
- The numerous potential trajectories both for Andromeda and the Milky Way
The Long Wait: Thousands of Years Ahead
Ultimately, researchers conclude that time will help unravel this mystery, though we are discussing timescales far beyond human lifespan—billions of years into the future. If a merger were to occur, it would take place long after our Sun has extinguished its last rays. Humanity may either perish along with our star or advance its capabilities to navigate between solar systems, opening the potential for limitless resources.
Conclusion: The Interstellar Dance
As we explore the depths of space and our understanding of galactic dynamics, the potential collision of the Milky Way and Andromeda remains uncertain. Future advancements in celestial mechanics may further illuminate these intricate cosmic relationships.