Astronomy for all
Wednesday January 18th 2012

M31-Milky Way simulated collision

 It may be a few billion years away(about 4.5), but it is believed that the two largest galaxies in our local group will merge.   The radial velocity of the Andromeda galaxy with respect to the Milky Way can be measured by examining the Doppler shift of spectral lines from stars in the galaxy, but the transverse velocity cannot be directly measured. Thus, while it is known that the Andromeda galaxy is getting closer to the Milky Way by about 120 km/s, there is no way to tell whether it is going to collide or miss.  There are lots of examples from Hubble of galaxy collision as shown below.

Galaxy Collision: Picture Source: NASA, Hubble Space Telescope

You can  get a much closer look using a zoomable image of the Antenna Galaxies at the NASA website. 

There is also a  cool simulation of what the Andromeda and Milky Way merge might actually look like.

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