By Divya Rajagopal
For many years, the astronomers at NASA have been speculating about the real “doomsday”. Well, the world didn’t end in 2012 as it was supposed to, so when will it? After years of calculations, 22 years to be exact, the NASA Hubble Space Telescope team has predicted with certainty that the Milky Way will die in 4 billion years as a result of a galactic collision with our neighbouring galaxy, Andromeda.
A little about the sky
Andromeda, which is also known as M31, is 2.5 million light-years away. It is fast approaching the Milky Way at a speed of about 110 kilometres per second due to the gravitational pull (the speed equal to travelling to the moon in an hour). It has been certain for some time that there will be a collision but research was on-going about the exact details. The Hubble Space Telescope team discovered that it would be a head-on collision, leaving no possibility that the Milky Way would survive.
The Milky Way-Andromeda collision
There will be two phases of the Milky Way-Andromeda collision. The first will be the collision as such. The gravitational pull of the two galaxies is responsible for the momentum they have towards each other. The good news is that the chances of the stars of Milky Way and Andromeda colliding are negligible. For example, the nearest star to the Sun is Proxima Centauri, about 4.2 light-years away. If the Sun were a ping-pong ball, Proxima Centauri would be a pea about 1,100 km away.
It has also been recently found that the Andromeda is not the only galaxy that will get caught up in the action. M31’s small companion, a Triangulum galaxy, M33, will join the collision too. It is speculated that M33 will hit the Milky Way first.
The Merger
The second phase of the collision will be the merger. Since the two galaxies have a strong gravitational pull, they won’t be able to pry apart from each other after the collision. The frisbee-shaped Milky Way and the Andromeda, which is a spiral, will combine to form a new ellipsoid galaxy. The merging process of the two galaxies is predicted to take another 2 billion years. The stars of the two galaxies will find themselves in different orbital positions after the merger. However, it has been estimated that the two black holes currently at the centre of both galaxies will converge near the centre of the newly-formed entity.
What about our Solar System?
There is a 50% probability that in the merged galaxy, the Solar system might be swept away from the galactic core. There is also a 12% chance that the Sun might be ejected from the merged galaxy. The Sun and the Earth might survive the collision but there will be no way to truly find out. During this time of planetary engineering, the surface of the Earth will already be too hot for liquid water to exist, so all life on the planet will long have been extinguished.
The next step forward
During recent space shuttle servicing missions, NASA upgraded the Hubble Telescope with even more powerful cameras. These will help the astronomers to make the critical measurements needed to nail down M31’s motion. But, for now, all that remains certain is that the Milky Way will die forming a new galaxy and its likely the human race won’t be around to name it.
Featured image source: Unsplash