The Milky Way and Andromeda: A Cosmic Collision Course

The cosmic catastrophe that will change everything (and how to prepare for it)
The Milky Way is on a collision course with Andromeda. Don’t worry, it will only happen in 4 billion years. Plenty of time to pack your bags.


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For those in a hurry

  • The Milky Way and Andromeda are the two largest galaxies in the Local Group.
  • They are moving towards each other at about 110 km/s due to gravity.
  • They will collide in about 4.5 billion years and merge into a new galaxy called Milkomeda.
  • The stars are so far apart that they will not crash into each other, but some may be ejected from the new galaxy.
  • The sun and the Earth will survive the collision, but they may end up in a different location in the galaxy.

How do we know this?

  • Astronomers used the Hubble Space Telescope to measure the motion of Andromeda relative to hundreds of distant background galaxies.
  • They found that Andromeda is moving southeast in the sky at less than 0.1 milliarc-seconds per year, which means it is heading straight for us.
  • They also used computer simulations to predict how the collision will unfold over the next several billion years.

What will it look like?

  • The collision will be a spectacular show in the night sky, but it will take a long time to complete.
  • As Andromeda gets closer, it will appear larger and larger, eventually filling the whole sky.
  • The two galaxies will twist and distort each other with tidal forces, forming long streams of stars and gas.
  • The galactic cores will pass through each other, then swing back and forth until they settle into a new center.
  • The new galaxy will be an elliptical shape, unlike the spiral shapes of the original galaxies.

Why should we care?

  • The collision of the Milky Way and Andromeda is a rare and fascinating event that reveals the nature of galaxies and their evolution.
  • It also shows us how small and fragile we are in the vastness of space and time.
  • It reminds us that nothing lasts forever, not even the stars and planets we call home.
  • But it also gives us hope that life can endure and adapt to cosmic changes, as long as we don’t destroy ourselves first.