What will happen during Collision of Milky Way with Andromeda Galaxy?

Andromeda Galaxy
Andromeda Galaxy is 50% bigger than our Milky Way. (Credit: NASA)

You must have heard about the collision of an asteroid with the planet and aware of the destruction that can be caused by such an event. But there is one bigger cosmic event that is the collision of our Milky Way Galaxy with the Andromeda Galaxy. These two galaxies will merge to form a new galaxy in future. This was the common process of formation of new galaxies after the big bang.

Before talking about collision let us first look at these galaxies. Milky Way is a spiral galaxy consisting of nearly 100 billion stars and has the diameter of nearly 100,000 light years. Our sun is present in the middle of the spiral arm and revolves around galaxy within the spiral disk.Our galaxy is part of a local group of galaxies which has nearly 50 big or small galaxies.

Andromeda Galaxy is our neighbouring galaxy which is spiral in shape with diameter 50 % more than the Milky Way. Andromeda Galaxy is present at the distance of 2.5 million

Our galaxy is part of a local group of galaxies which has nearly 50 big or small galaxies. Andromeda Galaxy is our neighbouring galaxy which is spiral in shape with diameter 50 % more than the Milky Way. Andromeda Galaxy is present at the distance of 2.5 million light-years from us.

In early years of 20th century, Hubble and many other astronomers observed that the galaxies are moving away from each other which lead to the expanding universe then why this Andromeda Galaxy is moving towards us.

As we know that these two galaxies are part of the local group, so they are bound by the gravitational interaction which is bringing them close to each other. Andromeda galaxy is moving towards Milky Way with the velocity of 250000 miles/h.

Collision of Milky Way with Andromeda Galaxy
The Milky Way and Andromeda are moving toward each other under the inexorable pull of gravity. Also shown is a smaller galaxy, Triangulum, which may be part of the smash up. (Credit: NASA; ESA; A. Feild and R. van der Marel, STScI)

“After nearly a century of speculation about the future destiny of Andromeda and our Milky Way, we, at last, have a clear picture of how events will unfold over the coming billions of years,” says Sangmo Tony Sohn of the Space Telescope Science Institute (STScI) in Baltimore.”Our findings are statistically consistent with a head-on collision between the Andromeda galaxy and our Milky Way galaxy,” adds Roeland van der Marel of the STScI.

“Our findings are statistically consistent with a head-on collision between the Andromeda galaxy and our Milky Way galaxy,” adds Roeland van der Marel of the STScI.

Next question arises, when will these two galaxies collide?

In spite of moving with such a high velocity, Andromeda Galaxy will take 3 billion years to reach Milky Way and another one billion years will be required for formation of a new galaxy. The Collision may become complicated because of another galaxy called Triangulum (M33) which may join the collision during the period when two galaxies will be merging into each other. Whether Triangulum Galaxy will reach before or after Andromeda Galaxy, it is still not clear.

Illustration of Collision of Milky way with Andromeda Galaxy
This series of photo illustrations shows the predicted merger between the Milky Way and Andromeda as seen from the Earth. The first frame is the present day; the last frame is 7 billion years from now. (Source: NASA, ESA, Z, Levay and R. van der Marel (STScl), T. Hallas, and A. Mellinger )

An important question is still there, what will happen to galaxies during the collision? Will it harm the Earth?

When two galaxies will merge, there centres which have big black holes tries to engulf each other but the other revolving stars in the spiral arms will not be harmed due to vast empty space between them. Star collision will be rare in spiral arms. The transformation of two centres into one centre is not so peaceful because due to gravity the pressure increases on the clouds and material of centre which results in the high temperature and formation of new stars. Supernovae and X- ray emission will be there. The rate of generation of new stars is as high as 100 times of normal rate. The centre of the new deformed galaxy will be glowing for millions for years due high formation new stars and finally with the end of raw material the centre will become dark and fade.

All this rearrangement will not affect our sun and solar system. Our sun along with its solar system will be thrown into the new region of the galaxy. There are two possibilities, one is the Sun will be thrown towards the edge of galaxies where we will have very few stars in the sky and our sky will be much darker than today. Now, the Sun will revolve around the newly formed galaxy. The other possibility is slightly dangerous which will include the throwing of the Sun towards the centre where X- ray emission may harm us. But we do not need to worry about that because in these 4 billion years, the Sun will run out of fuel and grow in size which will result in the destruction of life due to heat.

Anyway there is rare possibility that this collision will harm solar system or Earth. For example, according to these scientists: It is likely the sun will be flung into a new region of our galaxy, but our Earth and solar system are in no danger of being destroyed.

References:

http://earthsky.org/space/milky-way-and-andromeda-galaxies-to-collide-when-four-billion-years

http://csep10.phys.utk.edu/astr162/lect/galaxies/colliding.html

http://cas.sdss.org/DR3/en/proj/basic/galaxies/collisions.asp

http://www.galaxydynamics.org/tflops.html

http://science.nasa.gov/science-news/science-at-nasa/2012/31may_andromeda/

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