DEATH OF THE MILKY WAY – THE ANDROMEDA-MILKY WAY COLLISION

You’d probably be scared if I told you a huge asteroid is going to collide with our planet sometime in the future, right? Of course you’d be, anyone would be. Now forget the asteroid, what if I told you an entire galaxy is coming your way, racing towards you at the speed of 110 Km/s and would smash into all of us one day eventually? Yes, you heard it right, an ENTIRE GALAXY would collide into our beloved Milky Way & the countdown is already on. 

So, come let’s dig into this Game of Galaxies. Fasten your seat belts & brace for the impact!

THE JOURNEY

Andromeda is our closest neighboring galaxy, 2.5 million light years away from us. If I was to write this distance in kilometres, it would have 20 digits, so yes, it’s a huge distance!

Fueled by gravity, the galaxies are moving towards each other at a speed of 110 Km/s or 402,000 Km/h. To put this speed into perspective, moving at 110 km/s, you could go around the Earth in just 6 minutes. 

(Source : https://www.nasa.gov/mission_pages/hubble/science/milky-way-collide.html)

After 4 Billion years, the first contact between the two galaxies would happen, the galactic collision would begin, and would continue to take place over the span of another 2 Billion years.

THE SHOW BEGINS

As the galaxies would close in, one would see Andromeda getting bigger and bigger in the night sky. However, the magnificent spiral in the sky would be just the beginning, soon a show of cosmic choreography would begin, a dance of stars & planets on the rhythm of gravity would follow in one of the most ecstatic galactic collisions the human race might ever come to experience.

Below is an illustration by NASA on what a person on Earth would witness in the sky, during the course of 6 Billion years. Each picture differs by roughly 0.7 Billion years, which means the first picture is the night sky, today, and the last one is the night sky, 6 Billion years later.

(Source : https://www.nasa.gov/mission_pages/hubble/science/milky-way-collide.html)

During the course of 4 Billion years, Andromeda would keep getting closer and closer to us, until we have touchdown. Now the collision finally begins, we’re in the endgame.

ENDGAME

So, what happens next?

Well, simply put, now the two galaxies would “collide”. However, a galactic collision differs greatly from a collision of two solid objects, like footballs because of what galaxies are made up of and how they work. A galaxy is a gravitationally bound system of stars, dust, gas & planets. They generally also have a Black Hole at their center, which holds the complete system together. 

Enough with the theory, now let us visualize the collision. 

So, arrange two pieces of transparent paper, and make a disk outline on both of these. Fill this disk with tiny dots using your pen, make a lot of dots. Do the same for both the papers. Now, overlap the two papers. You would notice some dots overlap, while some do not. 

The disk is the galaxy, the dots are the stars. The overlapping dots are the stars that would collide into each other, while the non-overlapping ones are the ones who would survive without a scratch. 

This is a simulation by NASA where you can see how the showdown would happen.

(Click the image to open the link)

So, now the two galaxies & their central black holes would merge over the course of another 2 billion years to form a new central black hole & a new system of stars & planets around it. The two galaxies would combine to form a new galaxy!

But what happens to the stars and planets, wouldn’t all of them collide and get destroyed?

Yes, some would. But surprisingly enough, most stars & even our solar system might survive the collision, the reason is that stars have a lot of empty space between them, so it gets really difficult for two stars to land at just the right spot to collide. Most stars would pass right beside each other. 

THE AFTERMATH

The darkest of nights lead to the brightest of mornings.

After 6 Billion years, as the dust settles, things would start to calm down. The stellar cosmic choreography would come to an end and the two galaxies would become one, the “Milkdromeda”.

The galaxy would contain a much bigger, Super Super Massive Black Hole at its center and our solar system would probably be thrown out somewhere on the outskirts of the galaxy.

But where would we be?

It’s incredible how much our humankind has advanced into technology & space exploration. As time passes by, newer technologies arrive, discoveries are made, and we make one more step into deep space, far away from our Earth and Solar System.

But we would soon be put to a test. Much before the galaxy comes racing our way, our own Sun would end up consuming us. In 1 billion years, it would be so luminous it would evaporate all the water on Earth! LIfe on Earth as you know it, wouldn’t be possible and it’s evident that we need to leave!

Our survival is on the line, the humans to come would be the ones who’d have to make us an intergalactic race, they’d have to migrate to another stellar system, go out into the unknown, so that a kid like me, or a kid like you, would then be able to look up in the sky, and see what we would miss.

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