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Title: The Milky Way Might Not Crash Into the Andromeda Galaxy After All

Link: https://science.slashdot.org/story/25/06/03/0...

New simulations suggest that the long-assumed collision between the Milky Way
and Andromeda galaxies is not guaranteed, with the odds now estimated at just
over 50% within the next 10 billion years. Factoring in other massive
galaxies like M33 and the Large Magellanic Cloud revealed that their
gravitational influence significantly alters the likelihood of a merger.
ScienceAlert reports: The Milky Way and Andromeda are not, however, alone in
this little corner of the cosmos. They belong to a small group of galaxies
within a radius of about 5 million light-years from the Milky Way known as
the Local Group. The Milky Way and Andromeda are the largest members, but
there are quite a few other objects hanging out that need to be taken into
consideration when modeling the future. [Astrophysicist Till Sawala of the
University of Helsinki] and his colleagues took the latest data from the
Hubble and Gaia space telescopes, and the most recent mass estimates for the
four most massive objects in the Local Group -- the Milky Way, Andromeda, the
Triangulum galaxy (M33), and the Large Magellanic Cloud (LMC). Then, they set
about running simulations of the next 10 billion years, adding and removing
galaxies to see how that changed the results. Their results showed that the
presence of M33 and LMC dramatically altered the probability of a collision
between the Milky Way and Andromeda. When it is just the two large spiral
galaxies, the merger occurred in slightly less than half the simulation runs.
The addition of M33 increased the merger probability to two in three. Taking
M33 back out and adding LMC had the opposite effect, decreasing the
probability to one in three. When all four galaxies were present, the
probability of a merger between the Milky Way and Andromeda within 10 billion
years is slightly more than 50 percent. "We find that there are basically two
types of outcomes," Sawala said. "The Milky Way and Andromeda will either
come close enough on their first encounter (first 'pericenter' that
dynamical friction between the two dark matter haloes will drag the orbit to
an eventual merger, which very likely happens before 10 billion years, or
they do not come close enough, in which case dynamical friction is not
effective, and they can still orbit for a very long time thereafter." "The
main result of our work is that there is still significant uncertainty about
the future evolution -- and eventual fate -- of our galaxy," Sawala added.
"Of course, as a working astrophysicist, the best results are those that
motivate future studies, and I think our paper provides motivation both for
more comprehensive models and for more precise observations." The research
has been published in Nature Astronomy.

Read more of this story at Slashdot.

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