Andromeda-Milky Way collision

The Andromeda-Milky Way collision is a predicted galaxy collision, due to take place in approximately three billion years time, between the two largest galaxies in the Local Group, the Milky Way and the Andromeda GalaxyHazel Muir, " [http://space.newscientist.com/article/dn11852-galactic-merger-to-evict-sun-and-earth.html Galactic merger to 'evict' Sun and Earth," "New Scientist" 4 May 2007] ] [Astronomy, June 2008, page 28, by Abraham Loeb and T.J.Cox] . It is often used as an example of the kind of phenomena associated with such collisions in simulations. [cite web|url = http://www.foxnews.com/story/0,2933,272562,00.html|title = Andromeda Galaxy May Steal Our Solar System From Milky Way] 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, 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 three billion years. [cite news|author=Young, Kelly|title=Galactic collision — a taste of things to come?|work=New Scientist|date=2006-08-26|url=http://space.newscientist.com/article/dn7916] If the collision occurs, the galaxies will likely merge into one larger galaxy. Various names have been proposed for the resulting merged galaxy, the most dominant being "Milkomeda".

It is worth noting that 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 (or "proper motion") cannot be directly measured. Thus, while it is known that the Andromeda galaxy is getting closer to the Milky Way by about 120 km/sec, 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/sec [Abraham Loeb, Mark J. Reid, Andreas Brunthaler, and Heino Falcke [http://www.journals.uchicago.edu/doi/abs/10.1086/491644 "The Astrophysical Journal, 633":894–898] , November 10 2005] . 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 around 2011, is intended to measure the positions of stars in the Andromeda galaxy with sufficient precision to pin down the transverse velocity.

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. [ [http://hubblesite.org/newscenter/archive/releases/galaxy/2002/09/text/ "Hubblesite Newscenter:" Hubble Astronomer Creates Spectacular Galaxy Collision Visualization for the National Air and Space Museum] ]

Such collisions are relatively common—Andromeda, for example, is believed to have collided with at least one other galaxy in the past. [ [http://www.msnbc.msn.com/id/16872449/ "Andromeda involved in galactic collision"] MSNBC 10:38 a.m. PT 29 January 2007] It is possible, but not certain, that our Solar System may be ejected from the new galaxy some time during the collision. Such an event would have no adverse effect on the system (especially since Sun is projected to enter red giant phase in 5-6 billion years). Chances of any sort of disturbance to the Sun or planets themselves are remote.cite web|title=When Our Galaxy Smashes Into Andromeda, What Happens to the Sun?|author=Cain, Fraser | work=Universe Today|url=http://www.universetoday.com/2007/05/10/when-our-galaxy-smashes-into-andromeda-what-happens-to-the-sun/|year=2007|accessdate=2007-05-16] [cite journal|title=The Collision Between The Milky Way And Andromeda | author=Cox, T. J.; Loeb, Abraham | journal=Monthly Notices of the Royal Astronomical Society | id=arxiv|0705.1170 | year=2007 | doi=10.1111/j.1365-2966.2008.13048.x|volume=386|pages=461]

References

Bibliography

* [http://www.cita.utoronto.ca/%7Edubinski/tflops/ The Merger of the Milky Way and Andromeda Galaxies] University of Toronto (website), John Dubinski, January 2001 (includes simulation)
* [http://haydenplanetarium.org/resources/ava/page/index.php?file=G0601andmilwy "Milky Way–Andromeda Galaxy Collision"] , Haydenplanetarium.org, John Dubinski (University of Toronto)
* [http://www.msnbc.msn.com/id/11605847/#storyContinued "Milky Way, Andromeda had similar origins"] MSNBC 8:11 p.m. PT 28 February 2006
* [http://www.msnbc.msn.com/id/16872449/ "Andromeda involved in galactic collision"] MSNBC 10:38 a.m. PT 29 January 2007
* [http://www.newsandevents.utoronto.ca/bin/000414b.asp "Astrophysicist maps out our own galaxy's end"] University of Toronto (website), by Janet Wong, April 14 2000
* [http://www.space.com/scienceastronomy/astronomy/galaxy_collides_020507-1.html "Crash Course: Simulating the Fate of Our Milky Way"] By Tariq Malik, SPACE.com Staff Writer, posted: 07:00 a.m. ET 7 May 2002
* [http://www.nasa.gov/audience/forstudents/5-8/features/F_When_Gallaxies_Collide.html "Milky Way vs. Andromeda"] NASA (website)
* [http://cfa-www.harvard.edu/press/pr0628.html "Busted! Astronomers Nab Culprit in Galactic Hit-and-Run"] Harvard University (website) Press Release No.: 06-28, October 18 2006
* [http://planetquest.jpl.nasa.gov/news/collision.cfm SIM PlanetQuest to predict date of cosmic collision] NASA/JPL PlanetQuest, January 4 2007