Is there any process known (even theoretical/mathematical) that a star can spit into 2 or multiple stars? Has anything like this been observed as having happened?
A collision.
Or if one part of it is denser than the rest, and the rotation is fast enough, it can split off and form a new star.
Rotation would be tough, because then you’d have to account for how it ever became a single star to begin with. If it’s rotating fast enough to split right now, then it was rotating fast enough to split last year, too.
What about interaction with a third, more massive body like a neutron star or black hole? Perhaps a star could come close on a hyperbolic orbit and be spread apart enough to become two stars when it re-coalesces.
Won’t happen. A star disrupted this way will just disperse into gases. The gases may be captured in a disk around the BH, but they won’t recoalesce.
You have to understand that the gas in a star is extremely hot. The surface of the Sun, for example, is 5800 kelvins. But that’s just the surface; the temperature goes up the lower into the star you go. The core of the sun is millions of kelvins. Now with gases, the temperature is equivalent to the speed of the particles that make it up. Those hot particles that make up the Sun (protons and electrons, mostly) want to move really fast. The only thing keeping them from dispersing is the gravity. Take away the gravity by disrupting the star and they all fly off every which way.
Is that specific to gasses? I thought I was taught that was true in all matter.
Didn’t all stars form in the first place by gasses coalescing due to their own gravity, though?
Certainly many bigger stars have plenty enough mater in them to form two, or even many more, smaller stars.
Could have formed that way- there are binary stars and higher multiples. But an existing big star can’t split off into little stars.
The material coalescing would have been much cooler. The temperatures would increase as the bulk increased gravity.
As an analogy, the iron that makes up the earth’s core would have been fairly cool before the planet formed. As it grew, the iron collected and sunk to the core. There the pressure from gravity heated it, first to liquid iron and then to a ball of solid iron at extremely high pressure at the very center. If you took the pressure away, the solid would first return to liquid and then cool off again to a solid.
I’m not convinced. You’re not taking away the gravity, so it won’t be a bunch of free nuclei speeding away freely. The most energetic nuclei will escape, but the remaining ones will be cooler. Further, when the star is disrupted, the surface area will increase, and the hotter gasses will also be more exposed, so it will radiate a lot more energy, cooling the gasses more. The star will expand and stretch along its orbit, and will certainly lose some if its mass, but I don’t see how it will just disperse. The question I see is whether it can be stretched out enough that it will re-coalesce into two bodies, instead of back into only one.
Also, the majority of the gasses won’t be captured in a disk, since the star is coming in on a hyperbolic orbit. Most of the mass will leave again.
It’s true in gases and liquids, but the particles (atoms) in a solid are restrained in where they can go. They just vibrate faster in place as they get hotter. Eventually they will vibrate so fast they can’t stay in place any more, but that’s when the solid reaches its melting temperature.
Yes, but the temperature of the gas and dust clouds that collapse to stars start at about 20 Kelvins. That’s way, way cooler than the gases that make up a star.
The smallest stars (not counting brown dwarfs) have about 8% of a solar mass. So our Sun could, in theory, be partitioned into about 12 very small stars. But I said “in theory”, since there’s no mechanism that will cause this to happen.
Sorry. Think about it this way,. When a star making a close pass to a black hole, there’s only two possible outcomes:
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It gets tidally disrupted. This is where the tidal forces from the black hole overcome the star’s gravity that was holding it together. This is what I meant by taking away the gravity and is what I was talking about in my post. You can find lots of stuff on this by googling for >>black hole star disrupt<< or something similar. For instance, here’s a site with some animations based on emulations.
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It doesn’t come close enough for outcome 1. In this case, the star will be tidally stretched during close approach, but then will resume its spherical shape afterwards. The tidal forces were not strong enough to pull apart the core of the star, so everything goes back to the way it was before.
By stating “there’s only two possible outcomes”, you’re just assuming the answer. You haven’t shown that those are the only two possibilities There’s a a third possibility between 1 and 2:
1.5) The star is tidally disrupted, stretched out into a string much longer in one dimension than the other two. Afterwards, the gravity of the line keeps it together, but it’s so stretched out when it re-coalesces, it doesn’t form a single star, but two (or more). See for example the first simulation in your link. The yellow and white particles won’t recombine, since the white particles are gravitationally bound to the black hole, and the yellow are not . But that doesn’t mean the yellow particles won’t recombine to form a star. Possibly more than one, depending on their mass. And while some of the white particles will form a ring near the black hole, the remainder could combine to form a star in orbit around the black hole. Follow that simulation for years instead of just 22 days, and you may find that he’s already found a case where a star is split into two daughter stars.
That’s just a single simulation, with one value for the mass of the black hole, one value for the mass of the star, one value for closest approach, and one value of incoming velocity. I’ve got four parameters to play with. That doesn’t even include the age or composition of the star itself, or the spin of the star and black hole, and their orientations relative to the plane of the stars orbit. There’s no way you can hand wave away the possibility of two stars forming. We’ve already got a case that’s at least close, and there are just too many details to consider.
So far the only one that is not contested is panache45 input of a collision. In that I can see that one star impacting another could cause 2 new stars from the remnants of the 2 old ones. Yes it is a star splitting itself in two parts (which combine with a likewise splitting itself in two parts second star), but because of the two in two out nature of this it seems a bit lacking.
Could a collision produce more stars then initially went into it. The simple case is a low mass star colliding with a body that is just under the minimum weight of being a star may produce 2 stars, but perhaps that sub-steller mass would seem to be a gas giant and be ripped apart. Perhaps a burnt out star colliding with star could. Also could a collision of stars produce more stars then then the number that what when into the collision.
One way of looking at it would be via entropy. I’m not sure how best to calculate it, but I’m sure that a single large star would have a lower entropy than two smaller stars (as evidenced by the fact that the small stars can merge to form the large star without any external influence). For objects as large as stars, the entropy difference is presumably quite large. So you wouldn’t be able to split a star without some other object being present whose entropy could increase by an amount greater than the decrease in entropy of the star you’re splitting.
This is easy enough to do for the limiting case, i.e. black holes; and in fact, Johannes Koelmann has considered just this setting in a very nice blog post, giving first the argument why it can’t be done just splitting a single black hole (because the surface area, and thus, entropy of the resulting black holes would be smaller than that of their progenitor), and then showing how it can be done for certain black hole collisions. However, in a follow-up post, he has also demonstrated that these processes, while physically possible, are nevertheless vanishingly unlikely.
In how far this kind of reasoning can be applied to stars, though, I don’t know.
True, but you have to come up with an at least somewhat plausible mechanism for how a star could fragment into two or more other stars. I don’t think you have.
The idea you gave is essentially the same as the Jeans-Jeffreys tidal hypothesis for the formation of the solar system. There were a number of problems with it, most not relevant here since they show the hypothesis couldn’t have formed our specific solar system, but one was the same I gave above, The mass drawn out of the star is too hot to collapse. It’ll explode. Even if the mass drawn out is enough to form a small star, its temperature is that of a much larger star. It won’t be able to stay together.
Curiously, I couldn’t find a Wiki-page for the Jeans-Jeffreys hypothesis or I’d give a link to it.
Also note that the cooling mechanisms you gave above would not be significant in the short time that the tidal disruption would take. Cooling of astronomical objects is virtually always a very slow process, especially when it’s a radiative cooling, which it almost always is.
Erm, you might want to take another run at this one.
I’m not sure you’re being consistent with yourself, or with the principle that isolated systems spontaneously evolve towards increasing entropy.
erm, nothing inconsistent there. Large star, lower entropy than 2 smaller. To make 2 smaller would require increase in entropy of another system that is greater than the decrease of this one.
Should re read chronos’s post and parse it correctly.
:dubious: Seriously? You really don’t think the mechanism I gave rises to the level of plausible?
I don’t think I can ever give you an answer you’d accept, even if I could run simulations myself showing two stars emerge.
Well, when a mommy star and daddy star love each other very much …