More exact prediction of collision with Andromeda galaxy

[marcus]

A HST team measure the sideways motion of Andromeda so they can be definite about the collision.Here is a movie.
http://hubblesite.org/newscenter/archive/releases/2012/20/video/a/

Here are the technical papers that the movie and press releases are based on:
http://arxiv.org/abs/1205.6865
The M31 Velocity Vector. III. Future Milky Way-M31-M33 Orbital Evolution, Merging, and Fate of the Sun
Roeland P. van der Marel (1), Gurtina Besla (2), T. J. Cox (3), Sangmo Tony Sohn (1), Jay Anderson (1) ((1) STScI, (2) Columbia U, (3) Carnegie Observatories)
Comments: 58 pages, 16 figures, to be published in ApJ. Version with high resolution figures and N-body movies available at http://www-int.stsci.edu/~marel/M31/ . Press materials, graphics, and visualizations available at http://hubblesite.org/newscenter/archive/releases/2012/20

http://arxiv.org/abs/1205.6864
The M31 Velocity Vector. II. Radial Orbit Towards the Milky Way and Implied Local Group Mass
Roeland P. van der Marel (1), Mark Fardal (2), Gurtina Besla (3), Rachael L. Beaton (4), Sangmo Tony Sohn (1), Jay Anderson (1), Tom Brown (1), Puragra Guhathakurta (5) ((1) STScI, (2) U of Massachusetts, (3) Columbia U, (4) U of Virginia, (5) UC Santa Cruz)
Comments: 38 pages, 4 figures, to be published in ApJ. Version with high resolution figures and N-body movies available at this http URL . Press materials, graphics, and visualizations available at this http URL

http://arxiv.org/abs/1205.6863
The M31 Velocity Vector. I. Hubble Space Telescope Proper Motion Measurements
Sangmo Tony Sohn, Jay Anderson, Roeland P. van der Marel (STScI)
(Submitted on 31 May 2012)
We present the first proper motion measurements for the galaxy M31. We obtained new V-band imaging data with the HST ACS/WFC and WFC3/UVIS of a spheroid field near the minor axis, an outer disk field along the major axis, and a field on the Giant Southern Stream. The data provide 5-7 year time baselines with respect to pre-existing deep first-epoch observations. We measure the positions of thousands of M31 stars and hundreds of compact background galaxies in each field. High accuracy and robustness is achieved by building and fitting a unique template for each individual object. The average proper motion for each field is obtained from the average motion of the M31 stars between the epochs with respect to the background galaxies. For the three fields, the observed proper motions (mu_W,mu_N) are (-0.0458, -0.0376), (-0.0533, -0.0104), and (-0.0179,-0.0357) mas/yr, respectively. The ability to average over large numbers of objects and over the three fields yields a final accuracy of 0.012 mas/yr. The robustness of the proper-motion measurements and uncertainties are supported by the fact that data from different instruments, taken at different times and with different telescope orientations, as well as measurements of different fields, all yield statistically consistent results. Papers II and III explore the implications for our understanding of the history, future, and mass of the Local Group. (Abridged)
Comments: 42 pages, 13 figures, to be published in ApJ. Version with high resolution figures and N-body movies available at this http URL . Press materials, graphics, and visualizations available at this http URL

Here is a menu of short movies that the technical papers give a link to:
http://hubblesite.org/newscenter/archive/releases/2012/20/video/

 

[qraal]

Hard to imagine what a "collision" between two such diffuse entities as Galaxies will actually mean. The odds of star-to-star collisions are nigh on zero, except if globular clusters crash into each other. But the wave of star formation will be quite profound - the number of very large stars forming and shortly thereafter exploding will punctuate the chemical history of the combined Galaxy in an unimaginable way.