Currently, the Milky Way galaxy and its neighboring Andromeda galaxy are speeding through the universe at a rate of approximately 223,000 miles per hour (100 km/s), potentially leading to a galactic collision that could ultimately result in their mutual destruction.
But what are the chances of this cosmic collision actually occurring? Previous studies predicted the collision to happen in about 4 to 4.5 billion years, but a new study incorporating recent observational data and adding new variables found that the likelihood of the collision is far from certain. The research estimates that the chance of a collision within the next 5 billion years is less than 2%, while the likelihood within the next 10 billion years is around 50%.
The two galaxies are currently about 2.5 million light-years apart.
This study was published on Monday, June 2, in the journal “Nature Astronomy.”
Galactic mergers are not like car crashes or collisions between stars and planets, but rather a massive and complex fusion of celestial bodies.
“If a collision occurs in the future, both the Milky Way and Andromeda galaxies will be destroyed,” said Till Sawala, an astrophysicist at the University of Helsinki and the lead author of the study.
Sawala mentioned that the structures of both galaxies will be obliterated, and after merging, they will form a new elliptical galaxy from the two spiral structures. “If the merger happens, it is more likely to occur in about 7 to 8 billion years from now. However, based on current data, even if the merger does happen, we cannot predict the exact timing of it,” he stated.
One of the co-authors of the study, Carlos Frenk, a professor at Durham University in the UK, noted that collisions between other galaxies produce “cosmic fireworks,” where gases are driven into the center of the merger remnants, enter the central black hole, release significant radiation, and irreversibly fall into the black hole.
The potential collision is expected to occur in the distant future, and by then, the universe, the Milky Way, the solar system, and the region could be vastly different from what they are currently. The shape and total mass of the Andromeda galaxy are similar to that of the Milky Way.
Researchers utilized data from the Gaia telescope, the Hubble Space Telescope, various ground-based telescopes, as well as revised estimates of galaxy masses to simulate the movement of the Milky Way over the next 10 billion years.
The presence of other nearby galaxies also affects the likelihood of a collision. The study considered the gravitational influence of the Triangulum galaxy, also known as M33, which is about half the size of both the Milky Way and Andromeda, and the smaller satellite galaxy of the Milky Way, the Large Magellanic Cloud.
“We found that if only M33 is added to the binary system, the likelihood of the Milky Way merging with the Andromeda galaxy will increase, but adding the Large Magellanic Cloud will have the opposite effect,” Sawala explained.
The researchers concluded that the Milky Way and the Large Magellanic Cloud will almost certainly merge within the next 2 billion years.
The mass of the Large Magellanic Cloud is only about 15% of the Milky Way’s mass. However, the research team discovered that the Large Magellanic Cloud possesses a gravity perpendicular to that of the Andromeda galaxy, enough to alter the motion of the Milky Way, thereby reducing the likelihood of a merger between these two giant galaxies.
A noteworthy distinction between the Milky Way and the Andromeda galaxy is the mass of their central supermassive black holes. The Milky Way’s Sagittarius A* mass is about 4 million times that of the Sun. The corresponding black hole mass in the Andromeda galaxy is estimated to be around 100 million solar masses.
“The likelihood of collisions between stars is very low, but the two supermassive black holes will sink into the center of the newly formed galaxy and ultimately merge there,” Sawala added.
Galactic mergers have been occurring since the early universe, particularly in regions where galaxies cluster together.
“In the early universe, the frequency of galactic mergers was much higher, so the first merger should have occurred shortly after the first batch of galaxies formed,” Sawala explained.
(This article references reports by Reuters and CNN)