Q&A: Milky Way Galaxy

Q:
If the Milky way is 50 percent more massive then previously thought, by how much will that decrease the time before we approach, collide with Andromeda?

A:
Thanks for the question, which is a good one. They don't mention in the press release how much sooner they think the collision will occur, but I found this explanation in an article in Science News:

"The more mass in the big galaxies - the Milky Way and Andromeda - ... the sooner they will collide," says Reid. Researchers had previously calculated that the two galaxies will merge in about 5 billion years. Reid says he is not certain exactly how much sooner the two giants would collide because the full three-dimensional motion of each galaxy has not yet been determined. A heavier Milky Way might also have a greater retinue of satellite galaxies - tiny galaxies, like the Large and Small Magellanic clouds - that orbit it, he adds.

In other words, they haven't estimated a time yet.

You can see the full article at:
http://www.sciencenews.org/view/generic/id/39709/title/This_just_in_Milky_Way_as_massive_as_3_trillion_suns