- 4539 -
MILKYWAY and ANDROMEDA
GALAXIES COLLIDE? - Are Andromeda and the Milky Way doomed to
collide? Maybe not. There is a predicted
merger between our Milky Way galaxy and the neighboring Andromeda galaxy to
unfold over the next several billion years.
----------------------------- 4539 - MILKYWAY and ANDROMEDA GALAXIES COLLIDE?
- Scientists discovered the Andromeda galaxy,
known as M31, hundreds of years ago, and around a century ago, we realized that
it had negative radial velocity toward the Milky Way. In other words,
eventually, the two galaxies would merge spectacularly. That has been common
knowledge for astronomers since then, but is it really true?
-
- There are several confounding factors,
including the gravitational influence of other galaxies in our local group, and
these tell us there is a 50% chance that the Milky Way will merge with the
Andromeda galaxy in the next 10 billion years.
-
- That seems like a pretty big thing to get the
physics wrong on. So, how did the authors come to that conclusion? They
accounted for a problem that has been popularized in media as of late—the
three-body—or in this case, four-body—problem. And with that problem comes a
lot of uncertainty, which is why there's still a 50% chance that this huge
event might still happen.
-
- Thinking of Andromeda and the Milky Way in
isolation doesn't account for the other galaxies in what we know as the
"Local Group." This comprises approximately 100 smaller galaxies at
various orientations, distances, and speeds.
-
- The largest of the remaining galaxies is the
Triangulum galaxy, M33, which is about 2.7 million light-years away and
consists of upwards of a 40 billion stars. That's about 40% of the
approximately 100 billion stars in the Milky Way but a mere 4% of the nearly 1
trillion stars estimated to exist in Andromeda. Still, they would have their
own gravitational pull, contorting the simplistic dynamic between Andromeda and
the Milky Way.
-
- Further confounding that dynamic is the
Large Magellanic Cloud, which is either the second or third closest galaxy to
our own at a distance of only 163,000 light years. This is slightly larger than
the Milky Way's diameter, at 105,700. It also houses around 20 billion stars,
so while it's even less massive than M33, it still exerts a hefty gravitational
pull.
-
- The authors accounted for the gravitational
pull of both of those other galaxies in their calculations of the paths of the
Milky Way and Andromeda over the next few billion years. They found that the
complicated dance of astronomical giants could potentially result in a scenario
where the two galaxies don't merge. However, there was another significant
factor in their calculations: uncertainty.
-
- Scientists never like uncertainty. In fact,
much of their research tries to place bounds on certain parameters, like the
rotational speed of galaxies or the distances between them. Unfortunately,
despite their proximity, there are many uncertainties surrounding the four
galaxies used in the study, and those uncertainties make precise calculations
of the effects of their gravitational and rotational pull difficult.
-
- If it happens at all, a merger between the
Milky Way and Andromeda will happen long after our own sun has burned out, and
humans will either die out with it or find a way to expand to new stars.
-
- Andromeda and the Milky Way Galaxies doomed
to collide? Maybe Not. Scientists discovered the Andromeda galaxy,
known as M31, hundreds of years ago, and around a century ago, we realized that
it had negative radial velocity toward the Milky Way. In other words,
eventually, the two galaxies would merge spectacularly.
-
- That has been common knowledge for
astronomers since then, but is it really true? A new paper from researchers at
the University of Helsinki looks at several confounding factors, including the
gravitational influence of other galaxies in our local group, and finds only a
50% chance that the Milky Way will merge with the Andromeda galaxy in the next
10 billion years.
-
- That seems like a pretty big thing to get
the physics wrong on. So, how did the authors come to that conclusion? They
accounted for a problem that has been popularized in media as of late – the
three-body – or in this case, four-body – problem. And with that problem comes
a lot of uncertainty, which is why there’s still a 50% chance that this huge
event might still happen.
-
- The “Local Group.” of galaxies comprises
approximately 100 smaller galaxies at various orientations, distances, and
speeds. The largest of the remaining galaxies is the “Triangulum galaxy”, M33,
which is about 2.7 million light-years away and consists of upwards of a mere
40 billion stars. That’s about 40% of the approximately 100 billion stars in
the Milky Way but a mere 4% of the nearly 1 trillion stars estimated to exist
in Andromeda.
-
- Further confounding that dynamic is the
Large Magellanic Cloud, which is either the second or third closest galaxy to
our own at a distance of only 163,000 light years. This is slightly larger than
the Milky Way’s diameter, at 105,700. It also houses around 20 billion stars,
so while it’s even less massive than M33, it still exerts a hefty gravitational
pull.
-
- The authors accounted for the gravitational
pull of both of those other galaxies in their calculations of the paths of the
Milky Way and Andromeda over the next few billion years. They found that the
complicated dance of astronomical giants could potentially result in a scenario
where the two galaxies don’t merge. However, there was another significant
factor in their calculations: uncertainty.
- Developing estimates rather than concrete
numbers is one-way scientists often deal with uncertainty, and in this case,
that estimate fell right at the 50% mark in terms of whether or not the two
galaxies would collide. However, there is still a lot of uncertainty in that
estimate, and plenty more confounding factors, including the other galaxies in
the local group, will influence the final outcome.
-
- Ultimately, time will help solve the
mystery, but that is a very long time on the scale of galaxy mergers. If it
happens at all, a merger between the Milky Way and Andromeda will happen long
after our own Sun has burnt out, and humans will either die out with it or find
a way to expand to new stars. And if, at that point, we get easy access to an
additional galaxy’s worth of resources, it would be all the better for us.
-
-
August 19, 2024 MILKYWAY
and ANDROMEDA GALAXIES COLLIDE? 4539
------------------------------------------------------------------------------------------
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------ “Jim Detrick” -----------
--------------------- --- Tuesday, August 20,
2024
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