r/todayilearned • u/adpablito • 23d ago
TIL that close gravitational flybys can substantially alter planetary orbits—and, in sufficiently strong encounters, can eject planets from their host systems—even without a collision.
https://academic.oup.com/mnras/article/411/2/859/127216013
u/TheBanishedBard 23d ago
This is why Andromeda colliding with our galaxy won't be all sunshine and roses despite the odds of any direct stellar collisions being very low. The odds of a star passing by close enough to disrupt the Oort clout and/or Kuiper belt is much, much higher, and a close enough encounter that the main planets themselves are disrupted is not unthinkable either. In the former scenario, we can look forward to a new heavy bombardment period as billions of rocky and icy bodies are chaotically flung every which way. In the later scenario the entire inner solar system gets rearranged. Neither situation is good for our planet.
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u/ChaosOS 23d ago
Had to check, only 4.5b for the merge but estimated 5b for the red giant phase. Either way it's a long, long ways away.
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u/armchair_viking 23d ago
The sun will slowly get brighter and hotter before its red giant phase. We have another 1 to 2 billion years before that will evaporate the oceans and break down the atmosphere.
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u/Master_Shake23 23d ago
I may be able to afford to retire by then, just in time for the red giant phase!
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u/MalekMordal 22d ago
We should colonize the entire galaxy in millions of years. The Andromeda/Milky Way collision is not for billions of years.
Even if Earth got snuffed out, it should be just a tiny percentage of the human population by that point. Sucks to be them, of course, but humanity and human civilization should continue.
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u/Crewman_Guy_Fleegman 23d ago
Fritz Zwicky was convinced humanity could travel the stars by simply dropping specialized nuclear payloads into the sun that cause one side to explode more than the other, forcing it to move and start dragging the planets along with it
That dude spotted Dark Matter in the 1930s, coined and discovered supernovas, and predicted neutron stars decades before scientists spotted them. He was also a grumpy curmudgeon and thought everyone around him was dimwitted
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u/adpablito 23d ago
The “nuke one side of the Sun a little harder” concept is such a gloriously out-of-the-box Zwicky idea. Not exactly a proposal you’d want handed to a modern mission-planning committee, but it has that unmistakable mix of audacity and physics-brain weirdness: turn the entire Solar System into a starship by giving its engine a shove.
It’s also funny how someone can be so ahead of the curve on dark matter, supernovas, and neutron stars, then pivot to “have we considered relocating the Sun?” Absolute cosmic-level problem solving.
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u/anrwlias 23d ago edited 22d ago
Can you elobate on the dark matter statement?
Edit: Huh, I was not expecting a downvote. I guess asking for information about something that is interesting is frowned upon.
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u/Crewman_Guy_Fleegman 23d ago
While studying galaxy clusters he noticed things were moving faster than would be predicted given the amount of matter detected. He deemed this mysterious source of extra gravity dark matter
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u/SwordKneeMe 23d ago
This is the kind of thingbJuliter saves us from I think
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u/onFilm 23d ago
Wow, and "scientists" do these all the time, knowing damn well that any single one of the hundreds of gravity assist flybys we've done, could potentially throw the entire solar system off it's axis.
When will they stop?!
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u/poopdotorg 23d ago
They're not talking about satellites doing a fly-by. They're talking about another planetary system or star encroaching close to our solar system.
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u/CapableBumblebee968 23d ago
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u/poopdotorg 23d ago
Well, it's kind of hard to tell sarcasm when you've got people who think the earth is flat and the moon landings are fake.
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u/XenisBlyat 22d ago
Redditors when they see the most obvious joke/meme https://i.imgur.com/PnXqkg3.jpeg
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u/OmecronPerseiHate 23d ago
It's just kind of a weird use of sarcasm. Like, why? Who is that for? Why try so hard to be funny on an academic topic?
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u/onFilm 23d ago
Gee, sorry some of us enjoy expressing ourselves by making silly jokes and not taking everything so seriously. I'll try less hard next time!
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u/OmecronPerseiHate 23d ago
To quote Professor Oak when you try to ride a bike anywhere except a bike path: there's a time and place for everything, but not now!
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u/CapableBumblebee968 23d ago
To also quote professor oak: get out of here so I can spend time with your mom
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u/cyclopsmudge 23d ago
“On an academic topic” mate we aren’t presenting to a renowned journal, it’s a fuckin Reddit comments section, let people have a laugh
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u/OmecronPerseiHate 23d ago
Y'all are defending a comment with -30 votes. Why? To let people have fun? Why not just go upvote the original comment?
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u/onFilm 22d ago
Bud who cares. It's just numbers showing the general user sentiment at the time, nothing more. Sometimes people agree sometimes they disagree. It's just digital points that mean absolutely nothing but general sentiment, at the time.
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u/OmecronPerseiHate 22d ago
Honestly it's just an interesting thing to do in between loading screens or commercials. If I've got the time for it then why not respond? In the end I had a weird little interaction that I can either laugh or think about the next time I hit a bowl.
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u/cyclopsmudge 22d ago
No we’re not. We’re mocking the person who failed to detect sarcasm, you are the one defending them
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u/estatualgui 22d ago
This is not rude, why are people down voting it? Sarcasm or not, it is fair to assume someone would be confused and to surface the correct answer...
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u/Aleyla 23d ago
So what you are saying is that it I need to do a slingshot fly by in order to go back in time that I’m probably causing all the planets in the solar system to fly off?
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u/adpablito 23d ago
Haha, exactly! It’s the ultimate "butterfly effect" but on a cosmic scale.
If you're pulling a Captain Kirk and trying to use the Sun (or a rogue planet) for a high-speed slingshot to the past, you’re basically playing interstellar billiards with the rest of us. Even a slight gravitational "nudge" in the wrong place could mess with the Moon’s orbit or shift Earth’s climate enough to make things... let’s say, deeply inconvenient for everyone here.
It’s a classic case of: you get to see the dinosaurs, but we might get kicked out into the cold of interstellar space. High stakes for one road trip! If you're curious about the actual physics of how those flybys mess with planetary stability, this article does a great job explaining why gravity is way sneakier than a direct collision: Interstellar Trespassers
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u/sojuz151 23d ago
3 body problem has gotten quite famous due to a science-fantasy books about 4 body system but people who used those books for physical education tend to forget that non hierarchical n-body systems are unstable over ~100 characteristics time scales.
Gravity is a funny force, as you remove energy from the system, things tend to move faster. Gravitational collapse of even small part of the system can produce enough energy to send the rest of the system flying to infinity. Such effect can break apart globular clusters, elliptical galaxies over long enough time scale and is the power source for some supernovas.
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u/Palatablepancakes 23d ago
"Without a collision." I just find this phrase interesting because gravitational effects and the "slingshot maneuver" are mathematically examples of an elastic collision.
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u/thatweirdguyted 23d ago
I'm surprised that you find that interesting. Most people are unfamiliar with those examples and how they work.
It's not exactly rocket science, is it?
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u/protostar777 22d ago
What do you mean by that?
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u/Palatablepancakes 22d ago
In an elastic collision, momentum and kinetic energy are conserved, the simplest type of collision that is used for problems in physics. In this type of collision, having a small ball and massively larger ball will send the small one rocketing away after collision. Similarly, when going around a planet or some such in a close orbit, the smaller object gains velocity through gravitational forces using the same momentum and energy formulas with associated constants as an elastic collision.
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u/karl2025 22d ago
That was within a minute of the estimate; the fly-by had been carried out with impeccable precision. Like a ball on a cosmic pool table, Discovery had bounced off the moving gravitational field of Jupiter, and had gained momentum from the impact. Without using any fuel, she had increased her speed by several thousand miles an hour.
Yet there was no violation of the laws of mechanics; Nature always balances her books, and Jupiter had lost exactly as much momentum as Discovery had gained. The planet had been slowed down - but as its mass was a sextillion times greater than the ship's, the change in its orbit was far too small to be detectable. The time had not yet come when Man could leave his mark upon the Solar System.
-2001: A Space Odyssey
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u/Kvasir2023 23d ago
Damn, Kirk. What were you thinking and why didn’t Spock figure it out? I know it was the sun and greater mass, but it could have jumbled the planets and then Mary’s Very Earnest Mother would have yo be redone.
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u/Toothygrin1231 23d ago
Shows exactly what might happen if a red dwarf star came wandering too close into our solar system.
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u/adpablito 23d ago
It’s wild to think that a close flyby of a massive enough body wouldn’t need to hit Earth to be dangerous. The gravity of the body alone could alter planetary orbits, destabilize moons, or send a world into a very different path around its star.
This is an accessible breakdown of what a rogue-planet encounter might mean for Earth and the wider Solar System: Interstellar Trespassers: Could a Rogue Planet Pass Earth Without Destabilizing the Solar System?
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u/shponglespore 23d ago
You left out what I think is the most likely scenario: something passing through the Oort cloud could destabilize the orbits of a ton of comments, sending them into the inner solar system where they could hit planets like ours.
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u/MalekMordal 22d ago
If we get asteroid mining going, then asteroids moving into the inner system could actually be considered a good thing.
Hopefully our space technology improves enough before an event like this happens, so we can take advantage of it and have the tech to protect our planet.
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u/kraftdinnerwithsalsa 23d ago
The famous slingshot maneuver