Andromeda–Milky Way collision

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The Andromeda-Milky Way collision is a predicted galaxy collision that could possibly take place in approximately 3 billion years' time between the two largest galaxies in the Local Group – the Andromeda Galaxy and the Milky Way which contains Earth.[1][2]

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[edit] Illustration

It is often used as an example of the kind of phenomena associated with such collisions in simulations.[3] As with all such collisions, it is unlikely that objects such as stars contained within each galaxy will actually collide, as galaxies are in fact very diffuse—the nearest star to the Sun is in fact almost thirty million solar diameters away from the Earth. (If the sun were scaled to the size of an American quarter, 24.26 mm (0.955 in), the next closest quarter/star would be 700 km [475 miles] away.) If the theory is correct, the stars and gas contained in Andromeda will be visible to a naked-eye viewer in approximately 2 billion years.[4] If the collision occurs, the galaxies will likely merge into one larger galaxy.

[edit] Uncertainty

There is, as yet, no way to know whether the possible collision is definitely going to happen or not. 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. The best indirect estimates of the transverse velocity indicate that it is less than 100 km/s.[5] This suggests that the dark matter halos, although possibly not the actual disks, of the galaxies will collide. A future European Space Agency spacecraft, the Gaia mission, expected to launch in the Spring of 2012, is intended to measure the positions of stars in the Andromeda galaxy with sufficient precision to pin down the transverse velocity.[1]

Frank Summers of the Space Telescope Science Institute has created a CGI visualization of the predicted event, based on research by Professors Chris Mihos of Case Western Reserve University and Lars Hernquist of Harvard University.[6]

Such collisions are relatively common however. Andromeda, for example, is believed to have collided with at least one other galaxy in the past.[7]

[edit] The fate of the Solar System

Two scientists with the Harvard-Smithsonian Center for Astrophysics stated that when, and even whether, the two galaxies collide depend on Andromeda's sideways speed.[1] Based on current calculations they predict a 50% chance that in a merged galaxy the solar system will be swept out three times further from the galactic core than it is currently located.[1] They also predict a 12% chance that the Solar System will be ejected from the new galaxy some time during the collision.[8] Such an event would have no adverse effect on the system and chances of any sort of disturbance to the Sun or planets themselves may be remote.[8][9]

By the time that the two galaxies collide, the surface of the Earth will have already become far too hot for liquid water to exist, ending all terrestrial life, which is currently estimated to occur in about 1b years due to gradually increasing warmth of the Sun.[10][11] (See also: Stellar evolution)

[edit] See also

[edit] References

  1. ^ a b c d Hazel Muir, "Galactic merger to 'evict' Sun and Earth," New Scientist 4 May 2007
  2. ^ Astronomy, June 2008, page 28, by Abraham Loeb and T.J.Cox
  3. ^ "Andromeda Galaxy May Steal Our Solar System From Milky Way". http://www.foxnews.com/story/0,2933,272562,00.html. 
  4. ^ Young, Kelly (2006-08-26). "Galactic collision — a taste of things to come?". New Scientist. http://space.newscientist.com/article/dn7916. 
  5. ^ Abraham Loeb, Mark J. Reid, Andreas Brunthaler, and Heino Falcke The Astrophysical Journal, 633:894–898, November 10 2005
  6. ^ Hubblesite Newscenter: Hubble Astronomer Creates Spectacular Galaxy Collision Visualization for the National Air and Space Museum
  7. ^ "Andromeda involved in galactic collision" MSNBC 10:38 a.m. PT 29 January 2007
  8. ^ a b Cain, Fraser (2007). "When Our Galaxy Smashes Into Andromeda, What Happens to the Sun?". Universe Today. http://www.universetoday.com/2007/05/10/when-our-galaxy-smashes-into-andromeda-what-happens-to-the-sun/. Retrieved 2007-05-16. 
  9. ^ Cox, T. J.; Loeb, Abraham (2007). "The Collision Between The Milky Way And Andromeda". Monthly Notices of the Royal Astronomical Society 386: 461. doi:10.1111/j.1365-2966.2008.13048.x. arΧiv:0705.1170. 
  10. ^ Schröder, K.-P.; Smith, R.C. (2008). "Distant future of the Sun and Earth revisited". Monthly Notices of the Royal Astronomical Society 386 (1): 155. doi:10.1111/j.1365-2966.2008.13022.x. arΧiv:0801.4031. 
  11. ^ Carrington, D. (2000). "Date set for desert Earth". BBC News. http://news.bbc.co.uk/1/hi/sci/tech/specials/washington_2000/649913.stm. Retrieved 2007-03-31. 

[edit] Bibliography

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