Gas giant collision.
- Thread starter parmasson
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Andrew Boulton
The Adminator
I think it would be messy. You'd probably get moons thrown out in random directions, and God knows what the GGs would do. If their cores miss, one or both might go for a wander through the system.
Depends on velocity. If we assume 100 kps closing velocity (which is only a bit over escape velocity, and is thus a minimum value) and that each object has a mass of 1.9e27 kg, total energy release is 2.4e36J, some large part of which would go into heating up the gas giants (average initial temperature, after collision, should be several hundred thousand kelvin). There may be some fusion caused by compression waves, and a large amount of gas will be scattered in space. If we assume that 1% of the energy is released as radiation within the first thousand seconds (which is a rough order of magnitude for the initial collision duration) power output is 2.4e31W, or about 60,000 times as bright as the sun, which at 5 AU drops down to 2,400x brighter.
Overall, unless the planet is lucky enough to be in the shadow of the star, this will be an extinction event for life in that solar system. The velocity of the remnant may also result in the remnant going into an extremely elliptical orbit, which will eject inner planets into interstellar space even if they survive the first effect.
Overall, unless the planet is lucky enough to be in the shadow of the star, this will be an extinction event for life in that solar system. The velocity of the remnant may also result in the remnant going into an extremely elliptical orbit, which will eject inner planets into interstellar space even if they survive the first effect.
Fritz_Brown
Super Moderator
Would you get any kind of stripping of the atmospheres? Since GGs are giant balls of gas, would one passing "through" another leave one as just a rock?
Edit: Well, I think Anthony sort of answered the question....
It wouldn't so much "strip" the atmosphere as blow it off dramatically. end edit
Edit: Well, I think Anthony sort of answered the question....
M
Malenfant
Guest
I should re-iterate that this would be a very unlikely event... I can't really think of any reason why this would happen (I dunno, maybe a black hole passing through a system throws planets into wobbly orbits that brings two gas giants together?). I guess it might be possible very early in a system's history if gas giants are in eccentric orbits that cross, but I really can't see it happening later on after things have stabilised.
But it would be pretty spectacular
But it would be pretty spectacular
The most likely cause for such an event would the the intersection of 2 solar systems.
As one passed through the other, orbits would be disrupted, the energy from the second star should raise temperatures dramatically. Every living soul in both systems would be trying like mad to catch a ride to somewhere safe. Religeous extremists would be trying to sabotage anyone from leaving so they would meet their intended fate.
Sounds like a great setting for a traveller adventure.
As one passed through the other, orbits would be disrupted, the energy from the second star should raise temperatures dramatically. Every living soul in both systems would be trying like mad to catch a ride to somewhere safe. Religeous extremists would be trying to sabotage anyone from leaving so they would meet their intended fate.
Sounds like a great setting for a traveller adventure.
M
Malenfant
Guest
Again though, that's very unlikely out here. There's a lot of space for stars to be in while they're orbiting the galactic core, the chance that two with planets come so close to eachother that their systems intersect is phenomenally low. It's probably more likely in the galactic core or in a globular cluster but not out here where stars are relatively spread out.
This doesn't affect the thought experiment of what would happen if they did collide, but I'm just saying that in a realistic TU it's incredibly unlikely to occur naturally.
This all happens during planetary formation. A Mars-sized body collided with Earth to form Earth's moon, so on a larger scale you could have two gas giants colliding with each other, once things are settled and most of the system material is used up then this doesn't happen, but it can be used to explain some rather large moons orbiting gas giants.
Well, lets see; lets take a more reasonable situation:
GG 1 is slowly spiraling in, and two is relatively stable.
As they approach each other, they begin to bulge towards each other; this becomes more disk-like as they approach.
Overall, once they capture, both are now spiraling inward together. Many of the moons are likely to be sucked up. Depending upon final orbital distance, they could wind up looking vaguely like a contact binary pair without the light, the larger sucking in the smaller ever faster.
Now, if it's a more direct "Smack" type meeting, you get a huge cloud which may coalesce into a planet, or a ring, or maybe even just be blown off into deep space, depending upon velocities, solar wind, and impact angles. Again, it's likely that the wholl mess is now spiraling inward or highly eccentric.
GG 1 is slowly spiraling in, and two is relatively stable.
As they approach each other, they begin to bulge towards each other; this becomes more disk-like as they approach.
Overall, once they capture, both are now spiraling inward together. Many of the moons are likely to be sucked up. Depending upon final orbital distance, they could wind up looking vaguely like a contact binary pair without the light, the larger sucking in the smaller ever faster.
Now, if it's a more direct "Smack" type meeting, you get a huge cloud which may coalesce into a planet, or a ring, or maybe even just be blown off into deep space, depending upon velocities, solar wind, and impact angles. Again, it's likely that the wholl mess is now spiraling inward or highly eccentric.
Incidentally, Scientific American published a study on stellar collisions several years ago, which suggested that they may occur (and account for anomalous blue giants in globular clusters).
I have no idea how much of the energy from a collision would actually be released as prompt radiation; it might be much much less than I suggested.
I have no idea how much of the energy from a collision would actually be released as prompt radiation; it might be much much less than I suggested.
Plankowner
SOC-13
I would tend to agree with Laryssa and think that early in Solar System formation, large body collisions might be much more common than they are today. While still unlikely, it could happen.
Some of the theories of how the Hot Jupiters got to be where they are assume that they formed farther out and spiraled in. If another GG was in the way, they might merge/collide.
Should something like that happen though, after a few million years you probably wouldn't be able to tell. Similar to the contact Binary star example. They only stay that way for a while then they merge into a single star. There was also an article about contact binaries in Astronomy several years ago. One of the authors even suggested that our sun could have been a contact binary in the early solar system, but that there would be no way to prove it now.
Some of the theories of how the Hot Jupiters got to be where they are assume that they formed farther out and spiraled in. If another GG was in the way, they might merge/collide.
Should something like that happen though, after a few million years you probably wouldn't be able to tell. Similar to the contact Binary star example. They only stay that way for a while then they merge into a single star. There was also an article about contact binaries in Astronomy several years ago. One of the authors even suggested that our sun could have been a contact binary in the early solar system, but that there would be no way to prove it now.
Which would take millions of years, I would think, and possibly disrupt any other smaller bodies in the system. I'm not sure how this could happen - wouldn't the GasGiant slingshot out of orbit (the much postulated "10th" planet theory) without direct contact?
M
Malenfant
Guest
Yes, stars can and do merge. But they're usually contact binaries that start off in very close orbit around eachother. Gas giants usually don't do that, and they haven't got magnetic fields strong enough to brake them like the merging stars do.
Terrestrial planets can collide and form large satellites because both target and impactor are around the same sort of size.
But the things hitting gas giants are more than likely to be the same sort of size as terrestrial planets (or smaller) at most. You just don't get jupiter-sized objects wandering around solar systems in random orbits. You can get terrestrial/asteroidal bodies doing that because their orbits are easily perturbable by more massive objects, but you can't get that with gas giants because they're so much more massive.
If you had a situation where a gas giant was spiralling in and hit another then I suspect what would happen is that they'd gravitationally affect eachother's orbit before any collisions happened so that one was either ejected from the system or torn apart or flung into a different orbit (and though the orbits may cross, the planets themselves may be on opposite sides of the sun at the time of the crossover). The chance of a collision is probably very low because of that, because unlike two terrestrial planets the jovians can affect eachother at a much larger distance because of their greater mass.
I really can't see any remotely likely scenario where gas giants can collide.
Terrestrial planets can collide and form large satellites because both target and impactor are around the same sort of size.
But the things hitting gas giants are more than likely to be the same sort of size as terrestrial planets (or smaller) at most. You just don't get jupiter-sized objects wandering around solar systems in random orbits. You can get terrestrial/asteroidal bodies doing that because their orbits are easily perturbable by more massive objects, but you can't get that with gas giants because they're so much more massive.
If you had a situation where a gas giant was spiralling in and hit another then I suspect what would happen is that they'd gravitationally affect eachother's orbit before any collisions happened so that one was either ejected from the system or torn apart or flung into a different orbit (and though the orbits may cross, the planets themselves may be on opposite sides of the sun at the time of the crossover). The chance of a collision is probably very low because of that, because unlike two terrestrial planets the jovians can affect eachother at a much larger distance because of their greater mass.
I really can't see any remotely likely scenario where gas giants can collide.
How about two star systems pass close to each other and they exchange gas giants in the process. No doubt if the stars pass close enough to each other, two gas giants could collide, and what if a super-terrestial planet rams a gas giant? some of that suff may end up orbiting the gas giant.
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Malenfant
Guest
You might as well say "what if a gas giant pops out of a pocket universe at random next to another one and hits it?".
Don't confuse "possible" with "likely". It's possible that all the molecules of milk that you've stirred and mixed into your coffee could spontaneously arrange themselves back into a separate masses of milk and coffee, but the likelihood is so low that it'll effectively never happen.
edit: used the wrong analogy originally
Don't confuse "possible" with "likely". It's possible that all the molecules of milk that you've stirred and mixed into your coffee could spontaneously arrange themselves back into a separate masses of milk and coffee, but the likelihood is so low that it'll effectively never happen.
edit: used the wrong analogy originally
Plankowner
SOC-13
OK Mal, I'm convinced that they may not COLLIDE, but they WOULD greatly affect each other. That in itself could be a fun scenario.
Laryssa, even if the Milky Way and Andromeda galaxies were to pass through each other right now, the chances of 2 stars coming close enough to each other to affect their solar systems are still almost nill. There is a LOT of empty space in a galaxy...
Now, early during formation, within a star cluster, or a globular cluster or the central hub of a galaxy, things are different, but you are not going to have habitable planets, or many planets at all, in those regions. So star collisions, or even near misses CAN happen, but EXTREMELY rarely and even then, probably no planets involved.
Globular clusters and galactic hubs have stars that have such a low metalicity that they probably don't have planets and star forming regions are so young, the planets probably haven't formed yet. Exceptions exist, but not many.
Laryssa, even if the Milky Way and Andromeda galaxies were to pass through each other right now, the chances of 2 stars coming close enough to each other to affect their solar systems are still almost nill. There is a LOT of empty space in a galaxy...
Now, early during formation, within a star cluster, or a globular cluster or the central hub of a galaxy, things are different, but you are not going to have habitable planets, or many planets at all, in those regions. So star collisions, or even near misses CAN happen, but EXTREMELY rarely and even then, probably no planets involved.
Globular clusters and galactic hubs have stars that have such a low metalicity that they probably don't have planets and star forming regions are so young, the planets probably haven't formed yet. Exceptions exist, but not many.
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