Web edition: May 31, 2012
Print edition: July 14, 2012; Vol.182 #1 (p. 10)
The monstrous Andromeda galaxy and the Milky Way are destined to hit head-on, not in a glancing blow, new observations from the Hubble Space Telescope show.
By precisely locating the same stars in Andromeda in 2002 and then again in 2010, astronomers at the Space Telescope Science Institute in Baltimore have calculated how the galaxy has moved against the background of deep space — confirming that the galaxy’s sideways motion is but a fraction of the speed at which it’s hurtling toward the Milky Way.
Andromeda is 2.5 million light-years away and closing in on the Milky Way at 250,000 miles per hour. The cosmic collision will transform the heavens into a hallucinogenic swirl 4 billion years from now. Calculations suggest that the sun will be tossed out during this galactic mash-up, to drift erratically in the eventual single, large galaxy that will coalesce from the two.
The work will appear in an upcoming Astrophysical Journal.
S.T. Sohn, J. Anderson and R.P. van der Marel. The M31 velocity vector. I. Hubble Space Telescope proper motion measurements. Astrophysical Journal, in press.
R.P. van der Marel et al. The M31 velocity vector. II. Radial orbit towards the Milky Way and implied local group mass. Astrophysical Journal, in press.
R.P. van der Marel et al. The M31 velocity vector. III. Future Milky Way-M31-M33 orbital evolution, merging and fate of the sun. Astrophysical Journal, in press.
R. Cowen: This just in: Milky Way as massive as 3 trillion suns. Science News. Vol. 175, January 31, 2009, p. 8.
R. Cowen. Foraging among the galaxies: Andromeda's dining habits are documented. Science News. Vol. 165, April 3, 2004, p. 213.
R. Cowen. Andromeda feasts on its satellite galaxies. Science News. Vol. 160, July 7, 2001, p. 5.