Astronomers detect burps of interstellar cannibal from 480 million light years away A multinational team of astronomers has discovered what happens when a large star accidentally eats a black hole or neutron star: it emits a catastrophically violent, galactic-scale burp that can be detected from over 450 million light years away. Stellar boffins have previously theorised what would happen in this situation, …
I'm sure there is flaw in my logic, but if two objects are co-orbiting each other, if one is able to grow large enough to encompass the other, would that not happen with whichever grew to super-giant state first?
[Edit] A quick skim of the paper (thanks for the link) suggests that there is more going on than the suggestion of just the size of the second star growing - there is talk of inspiraling which means they get closer together later.
Edit is correct. When 1st star collapses the two are far off from each other and it does not impinge on 2nd star. 2nd star and corpse of 1st star then slowly spiral in (were already spiralling in in fact before 1st star suffered corpsing) losing energy through gravitational radiation (much too weak and too low frequency to see with current detectors). 2nd star then starts process of corpsification, impinges on corpse of 1st star and ... big fireworks.
Stellar mechanics are the most awesome things that happen in this Universe - or at least, the most energetic.
To think of a supergiant star having a black hole ingest it from the inside. The mechanics of that must be simply insane. The fact that it all ends in a supernova is frankly not surprising. The fact that it expels trillions of times the sun's energy is just a testament to how the Universe can go beyond everything we think we know.
Space is awesome.
> if any of them made it out "by the skin of their teeth"?
Remember this is actually the second supernova in this system. They would have to leave before the first supernova, a long time ago, making it no different than any other star death. By the time this giant-compact merger happens, they've either already left, or it doesn't really matter anymore.
Note giants are (relatively) short-lived, and I can imagine close giant binary suns are not the cosiest place to raise a planet and allow it to live long enough in the habitable zone: Planets around binaries usually orbit a specific sun, which would be quite difficult if the suns are relatively close to each other. As for planets orbiting the gravitational center of both suns, they would be quite far away and extremely likely to get ejected. I don't think there were any higher life forms in that system.
The two compact objects will spiral into each other, most likely creating a black hole, if there wasn't one there before, or making the existing one larger. This will generate gravity waves that LIGO and Virgo will detect if the two compacts are large enough.
There's more to come!
"The ultimate result of all this interstellar argy-bargy is a pair of compact objects – black holes, neutron stars, or one of each – orbiting around each other as before, surrounded by an expanding cloud of very brightly shining gas."
And how does the matter inside the blackhole move in the outer universe? It can only move inwards towards the centre of the black hole. If it could move relative to the outer universe, it could escape the blackhole. So how are these moving around each other?
Ahh but you say, it doesn't actually move, space moves around it moves, distorting to move the blackhole around without actually moving the stuff of the inside of the black hole. As if the blackhole insides stay still, and the universe around it moves.... If I jump off a tree, does the universe distort space under me to move me to the ground? No? But its the same gravity effect. So perhaps then that 'space distortion' never made any sense.
"The remains of the first star, without the nuclear processes required to counteract the immense gravity its mass creates, will collapse into an ultra-dense neutron star or the gravitational singularity of a black hole, phenomena collectively known as compact objects."
Yet the gravity works in one direction, towards the highest mass, and the nuclear processes would have to oppose that direction to oppose that motion. How does that work? Does the nuclear processes know which direction they need to go? Are they non-symmetrical with respect to gravity?
Asking for a friend.
> the nuclear processes would have to oppose that direction to oppose that motion. How does that work?
Those "nuclear processes" are basically a thermonuclear explosion (think H bomb). How does an explosion know in which direction to explode? Well, it doesn't, it just explodes, and stuff flies the only direction possible, outwards (i.e. away from the center).
You can think of the process inside a sun as being a humongous thermonuclear explosion: A sun is a huge H bomb, continuously exploding as long as it has explosives fuel to burn. Now the star's huge gravity tries to counteract the explosion's "outwards flying" motion, till they reach an equilibrium which determines the apparent diameter of a sun (and explains why this diameter isn't always constant).
You can think of a "supernova" as a perturbation in that equilibrium: In the classical single-star case, fuel starts running out, so the "explosion" weakens, and gravity wins out, compressing the star even more (it gets smaller). This compression allows other, previously inert elements to start fusing (exploding), and that new explosion is so violent it beats gravity and manages to spill the stars innards all over the neighborhood. That's a supernova.
Obviously astrophysicists will howl, but this is indeed the simplified, layman version on why stars go "boom" when older...
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