You may be familiar with Andromeda, our closest neighboring galaxy. You may have also heard that Andromeda and our Milky Way are moving towards each other. But what will happen to Earth and the rest of our solar system when these two galaxies collide? Will Earth even still be around by then?
The answer to the second question is likely yes, at least based on the projected lifetime of the Sun. The Sun should live for about 10 billion more years. However, in about 5 billion, it will turn into a red giant and expand into Earth, burning it up. Humans will not be around to see that, unless we relocate to a different planet. Earth will stop being able to sustain human life in about 1 billion years, due to the Sun increasing in brightness and drying up the oceans.
As for Andromeda, it is expected to collide with us in about 4 billion years. With this timing, the Sun will not be a red giant yet, and therefore all the planets will still be intact unless something else happens to them. While a collision of galaxies sounds very catastrophic, scientists agree that it is unlikely that our solar system would be harmed in any way, due to how spread out stars are in each galaxy. The odds of any two stars in either galaxy crashing into each other are extremely low. The black holes at the centers of each galaxy would merge, with Andromeda’s black hole of 100 million solar masses swallowing ours, which is only 4 million solar masses. After this merge, computer simulations from Hubble data predict that it will take about 2 billion years for the contents of each galaxy to completely merge and reshape into one elliptical galaxy. While this reshaping takes place, it is predicted that our solar system will be thrown much further from the center of the galaxy than we are right now.
Although this collision of galaxies would be unlikely to affect the lives of anyone living in either galaxy, astronomers could have a pretty good time with the event. As Andromeda and the Milky way get really close together, it may be fun for any intelligent lifeforms to observe another galaxy so close up, especially since from Earth, much of our view of our own galaxy is obstructed by dust. Would you want to live through an event like this?
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