The Milky Way Might Not Crash Into the Andromeda Galaxy After All 49
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.
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.
Phew! (Score:4, Funny)
Re: Phew! (Score:2)
You can get reliable galaxy-collision prediction (Score:2)
First "they" say Andromeda and Milky Way will fly into each other, now "they say" they won't.
How can you plan our advanced human-minds downloaded into computing machinery civilization without reliable galaxy merger predictions?
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Ignore them.
In the event of a merger, the likelihood of two stars somewhere in the merged galaxies actually colliding is about 50%. 4 stars having two mergers, in the combined galaxies - about 25%. 8 stars in 4 merger events, about 12.5%.
Likelihood of a triple merger -close to zero.
Disruption of molecular clouds and new star formation - substantial, but given a billion or so
Re: Phew! (Score:1)
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The existential dread is over for me thought. They said it was uncertain whether the two galaxies would hit in ten billion years. That's enough for me to be scared. Imagine! In ten billion years! The horror!
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Damn, I was so looking forward to the spectacle :(
I think we have other things to worry about (Score:2)
Long before then Earth will become uninhabitable.
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Long before then Earth will become uninhabitable.
Actually Earth will not exist at all by then. In about 5-6 billion years our sun will run out of Hydrogen fuel, and will turn into a red giant, which will make Earth barren and without life. After another billion years in that state the sun will shrink, only to ignite massive amounts of Helium, and grow even larger in size than before, swallowing Earth. Finally it will shrink to a white dwarf star, and will still be cooling down when the galaxy crash may or may not happen in 10 billion years.
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In about 5-6 billion years our sun will run out of Hydrogen fuel, and will turn into a red giant, which will make Earth barren and without life.
At that point, the surface of the sun will be beyond Earth's current orbit, and this planet will just be a contaminant in the Sun's composition.
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That too is a matter of debate. Just HOW large the sun will expand to is still a bit up in the air. It will swallow Venus and Mercury almost certainly. Earth is in a "likey" zone but not assured. Even outside of that though, depending on the sun losing some mass as it expands the orbit of Earth could shift outwards a bit, so even if it encompasses Earth's current orbit, Earth might no longer be there.
But yes, Earth will indeed long be uninhabitable by then.
Humanity may or may not be extinct though. We'
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We'll have to learn how to turn space rocks of average composition (CHONSPFeNi) into a habitat. Not a natural habitat (feel free to propose your proposals ; but I bet it won't get through the Assembly of the People), but a high-redundancy collection of artificial habitats.
We might even find a naturally habitable planet - which could produce a schism between
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Terraforming a space rock is easy compared to that problem.
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Spin it. Live on the inside.
Even Newton understood inertia and it's pseudo-force consequence "centrifugal force" well enough to have worked that out, if he'd been posed with the question.
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It's about 50:50 whether the Sun's red-giant expansion will reach to Earth's current orbit, I agree.
I also agree that the Earth will be uninhabitable (no oceans ; possibly a Venusian climate) long before then. It might be as much as 2 billion years in the future, not 1 billion, but it's unlikely to be as long as 3 billion.
We may already have the technical capabilities for interstellar travel. Not the necessary experience, but we can envision how to do it. Just not as living individuals, as a living society.
Helium burning (Score:3)
I've studied the advanced-undergraduate textbooks on astrophysics in the Astronomy library at the U so you don' have to. Not saying that what is in those books is the last word, but it differs from the picture in more popular descriptions.
The Sun or any other long-lived lowish-mass star does not become a red giant by running out of hydrogen. It is only the core where hydrogen was fused during its Main Sequence lifetime that runs out, but there is the bulk of the hydrogen left outside the core.
What ha
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Yeah, you're not the only person here to have read university-level astrophysics textbooks. Even more think that reading a single article on IFuckingLoveScience is equivalent to actually getting a degree in astrophysics.
For clarification, that's Jupiter-diameter "size", and tens to hundreds of Jupiter-mass "size" (the density varies significantly thr
T Coronae Borealis (Score:2)
To quote the SCTV parody sketch Celebrity Blowup where celibrities known to over-act would literally explode in front of a TV audience, are you saying T Coronae Borealis could "blow up, real good!"? The literature I have seen is skeptical that ordinary novae, especially recurrent novae can retain enough mass after outbursts over time to blow up, real good in a Type Ia supernova.
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Never heard of "SCTV", and from that description, I wouldn't bother to watch it. Who cares what celebrities do to each other/ have done unto them?
There is a lot of research into recurrent novae, of which T CrB is the closest (known) and therefore the brightest (known). Fortunately there are some with considerably shorter cycles than T CrB, allowing a better view into their behaviour. Whether they blow off 99% of their accumulation each cycle, or 99.9%, or if the amount blown off is significantly variable, I
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Oh, and the third prospect for evolution of a recurrent nova system : the donor star gets a sudden dose of stellar hiccoughs - say, it swallows a gas giant, and does a sudden big release of gas, which piles up fast enough on the recipient to make it go Boom. Essentially, at random.
But it's unlikely that a donor star would be precisely stable in it's mass loss rate - it is drinking at the Last Hydrogen Saloon, has already left the Main Sequence, and is evolving rapidly (in stellar terms) ; so what it throws
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Whether Earth will be swallowed is hotly debated (no pun intended). It's on the borderline of swallow-vs-non-swallow such that every new bit of research seems to shift the boundary back and forth across the threshold.
A key variable is how much mass the sun will lose before it swells to Earth's orbit. Surface instability typically spits off chunks of the expiring star such that it loses mass. Mass loss will move the orbits of the planets outward, giving Earth more margin, but how much mass is lost is not wel
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Long before then Earth will become uninhabitable.
And long before then Earth will become uninhabited.
Okay, no problem (Score:2)
They don't really need to completely crash into each other for me to collect on my bet, but I do hope Andromeda can beat the spread.
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Poor fools are more common than poor bookies.
Thanks for the reminder to check last week's lottery "lucky dip" tickets.
What a shame (Score:3)
It would have taken awhile, but colliding with the Andromeda galaxy would have been the easiest way for us to travel there.
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Givvit up! The rumors of Linux winning the desktop there are dubious. For one, they mostly use Andrix, which requires tentacles.
I wonder if after this piece of news... (Score:2)
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Not sure what you think an astrophysicist will have to contribute to the effort of eliminating PFAS. That's not really their specialty.
Well, that's embarrassing. (Score:3)
What's the point spread in Vegas? (Score:2)
galaxy crash (Score:2)
Got Published. (Score:2)
Win-Win.
PSAs work! (Score:2)
Those "Don't Drink and Orbit" public-service announcements paid off!
Define crash into (Score:2)
Misleading header, eventually WILL collide (Score:2)
Re: "Might Not"
Eventually it most likely will, it will just take longer than expected. Andromeda is headed in our general direction. The "dark matter halos" cause a kind of friction* such that when they pass, their relative motions will be turned into heat and radiation, causing each to slow down relative to each other.
It's kind of an elliptical spiral that gets closer on each pass [stackexchange.com] until they eventually merge. Initially it was believed it would take one or two passes before they mostly merged, but may inste
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Anyone got an explanation or best theory?
It's called "dynamical friction [wikipedia.org]". Not actual rubbing on things, but if you take an object moving along past a bunch of other objects, and they're all attacting each other via gravity, you get a net force opposite the direction of movement by the combination of all the "slingshot effects" from all the other bodies.
Wikipedia doesn't have a cartoon of this, if I only had a blackboard. Let's see if I can google up a cartoon.... Aha! This is 2025, of course there's a good youtube talk [youtube.com]
about it.
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Okay, thanks, but the outskirts of galaxies are quite sparse of "regular" matter, and thus friction would be very little relative to the mass of the galaxy. Friction from ordinary matter could slow the bodies a tiny bit if they pass mostly adjacent, but not by much.
Dark matter is believed to somehow cause friction based on some things I've read (don't have link yet), and it hangs out at the outskirts of galaxies, where early passes typically occur. Thus, I'm referring to what might be called "non-baryonic f
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Errr, no.
DM is distributed, probably spherically, around galaxies, with the highest concentration in the middle of the galaxy. It's not as closely concentrated as baryonic matter (because it's got fewer interactions, that's what the "dark" means), but when people model the mass distribution of a gravitational lens, for example, the put the centre-of-mass of th
Thank heavens (Score:2)
Thank heavens; this has been keeping me up nights.
Oh Man that was a close call (Score:2)
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Barring unforeseen events (e.g. close-encounter with a 2 Solar-mass star), no.
The Solar system will still exist. The Sun will be a cooling white dwarf ; the planets from Mars out will be in approximately the same orbits (slightly out - the Sun will have lost some mass by stellar wind while a red giant) ; Earth is a 50:50 for existing or not ; Mercury and Venus will be dirt in the Sun.
It could even contain humans - but they'd be living in artificial habitats, not natural ones.
Cone of uncertainty (Score:2)
Those of us who live near US coasts know about hurricane tracks, and how they're really hard to predict even a few days out. The predicted tracks for galaxies might not be quite as unpredictable, but in the space of 10 billion years, a lot can happen. That cone of uncertainty is really, really wide at this point.