Well, it is official and a certainty: in 4 billion years our Milky Way Galaxy and our closest big galactic neighbor the Andromeda Galaxy (M31) will collide head on. NASA announced in a live web cast on Thursday May 31 the results of precise observations done of M31 with the Hubble Space Telescope (HST).
For about a hundred years we have known that the two galaxies were speeding towards one another at about 250,000 miles per hour - roughly the distance to the Moon. What we didn't know until now, was the circumstances of any possible collision, when it might happen AND what it might look like.
Years of measuring the movement of stars within M31 using HST has now given us the when, how and possible visual result - thanks to computer simulations - of this collision and subsequent merger of the Milky Way Galaxy, M31 and possibly third galaxy, M33.
The galaxies will collide head on and then take another two billion years to finally complete the merger. The Sun and our solar system are expected to survive intact as will the stars of each galaxy as there is so much space between individual stars in each galaxy.
The Milky Way, Andromeda and M-33 are currently all spiral galaxies but will merge to become a giant elliptical galaxy. Our solar system is projected to be farther from the new galactic core than where we are now in the Milky Way.
Such collisions and mergers are seen throughout the Universe and were far more common when the Universe was younger and more compact than it is now.
M31 is currently the most distant object you can see with your unaided eye at about 2.5 million light years away and closing "fast" on our galaxy. It should be quite a sight in the distant future to see M31 filling our sky and seeing the cosmic dance of the galaxies unfold.
Read More About It and see the great video of the collision and merger: http://www.nasa.gov/mission_pages/hubble/science/milky-way-collide.html and
Sky Guy in VA