Astronomers have long believed that our Milky Way will eventually collide with the Andromeda Galaxy. A new study suggests we may be able to avoid that fate.
The spiral galaxy Andromeda is our closest neighbor, located 2.5 million light-years away. The two galaxies were thought to collide after moving closer together for billions of years.
“Cruising at 250,000 mph (402,336 km/h), it will collide head-on with our galaxy in about 4 billion years,” NASA said in a 2012 statement. “This will create a combined elliptical galaxy. It looks as though the Earth, Sun, and planets of our solar system will survive the collision but assume new coordinates in the cosmos.” Supermassive black holes will occupy the center of this new elliptical galaxy.
But new measurements from the Gaia and Hubble telescopes only increase the probability of this merger to 50:50. Previous calculations were based solely on the positions and movements of the Milky Way and the Andromeda Galaxy. The numbers we have now are more precise and we can now better observe other celestial bodies and include them in the equation.
One thing we already know is that if their orbits come within 200 kiloparsecs (6,172,000,000,000,000 km) of each other, they will collide and merge. If they do not come that close, they will continue their evolution separately.
Andromeda and the Milky Way are the two largest galaxies within the so-called “Local Group,” a collection of neighboring galaxies. Most of the other galaxies within the group are too small to have any real influence, but two are large enough to influence the potential merger: M33 and the Large Magellanic Cloud.
The research team created numerous simulations to predict the probability of a collision. If you only consider Andromeda and the Milky Way, the probability is 50%.
Other players involved
When the simulations include the galaxy M33, the collision probability increases to 66%. Including the Large Magellanic Cloud galaxy changes the probability again, this time to 33%.
“The inclusion of M33 increases the merger probability, while the orbit of the Large Magellanic Cloud is perpendicular to the orbit of the Milky Way and the Andromeda Galaxy, making their merger less likely,” the astronomers explained.
When all bodies in motion are taken into account, the many uncertainties leave room for very different results. However, the probability of a merger during the next 10 billion years remains uncertain.
This is the first time astronomers have been able to perform these calculations using modern data, and the researchers acknowledge that much work is still needed before they can be certain.
“(But) as it stands, claims about the impending doom of our galaxy appear greatly exaggerated,” they said.
