Fusion, sure. The catastrophic runaway fusion in the last few moments of a star’s existence before death in a nova or a supernova spawns all of the naturally-occurring elements heavier than iron. Again, it’s not exothermic–it sucks down energy like I drink bourbon, but in those moments there’s ample energy to spare from the cataclysmic kinetic energy of super-dense plasma colliding with itself at a significant fraction of lightspeed (in the case of a Type II supernova).
No, I was more wondering about fissioning stable “iron peak” elements. Everything I’ve read seems to talk about fission in the heaviest parts of the periodic table.
What you would get depends on how good your magic freeze ray is. If you can extract every bit of energy all the way to the core (quite a challenge with a very massive object like a star), it seems to me that electrostatic repulsion would eventually be overcome by weak-force binding, probably resulting in a big ball of “neutronium” (a giant atomic nucleus or neutron star). If, as would seem likely, you can only effectively draw heat off the surface, the increasing pressure of compaction would make the core get hotter. You would have to continually draw off an increasing amount of energy to get enough pressure-driven heat out of the center to prevent ignition. Where you would put that energy is a troubling question in and of itself (even “magic” has limitations).
Then, of course, you have general relativity to deal with. As the star contracts, its gravitational gradient gets steeper, causing time to dilate more toward the center. Your energy extraction must accelerate greatly to keep up with the difference in your frame of reference. At a rate that is not comparable to a supernova (which quickly blows off a lot of mass as it collapses), I doubt you could reach the neutronium threshold, meaning you would have a rather unstable ball of hydrogen and other stuff. But space is not an inert, empty void, there is lots of energy in the sparest vacuum, and some of it will get to tickling the core of your frozen star. It would not take much under those conditions. Ignition looks like it would be all but inevitable.
A ball of gas 0.08 solar masses can, indeed, form a small and very dim (red dwarf) star, with hydrogen fusion going on in its teensy-weensy core. However, this assumes that said ball of gas consists primarily of hydrogen, i.e. about 75% hydrogen. An ice cube, being frozen water, is only 11% hydrogen by mass – the rest being oxygen.
I submit to you that a 0.08 solar mass ball of water – or even a 0.33 solar mass ball of water – would have too low a hydrogen concentration to sustain nuclear fusion at its core, even if the material that formed the ball infell from an infinite height.
I’m not an astrophysicist but I thought any element would achieve nuclear fusion if it was raised to a high enough pressure and temperature. Is hydrogen required for the process?
I’m not astrophysicist either, but as far as I know it takes a massive star to fuse oxygen.
And more massive elements than even iron can fuse - it’s just a process that consumes energy instead of producing it for iron and anything more massive.
And how would that work? A laser would add energy, not subtract it.
Now if you could somehow make the Sun generate a laser, and pump that energy out via the laser, that would be some mega powerful laser, cutting across the galaxy like a hot knife through butter. But wouldn’t that take something like a core collapse?
Note: it would have to be a significantly powerful laser output to be more than the Sun is already dumping via electromagnetic radiation.
The assumption would be that the mass requirement of 0.08 is dictating the amount of material needed for the density to increase to a point where the temperature could increase enough to ignite fusion. So in this case the ice cube could still slowly collapse and heat up to above the required temperature. Now what happens as that occurs is a good question. The assumption was that since this would happen slowly the molecules would free up their atoms and then the atoms form a plasma state, and in that plasma state the density difference would migrate the oxygen to the center, while the hydrogen formed a shell around it. While on a mass basis the hydrogen would be smaller than the oxygen, on a volumetric basis the resulting protostar would be mostly hydrogen. So would the hydrogen portion be dense enough or hot enough to ignite? Maybe, maybe not.
It’s also possible that given the time required, starting with a solid object collapsing rather than a gas cloud, I wonder if enough heat or radiation might be radiated away before the temperature rose to the proper level.
Laser cooling is a thing. It works quite well for single atoms and molecules, although apparently progress is also being made on laser cooling of macroscopic objects (unfortunately, the most recent research I can find on the subject is a few years old).
Good point. Niven did use a magnetically-induced induced coronal mass ejection event plus magnetic containment to make the Ringworld’s sun lase as a system-wide self-defense system. I admired the chutzpah of making your star into one big laser pump.
MOD NOTE: There were two threads on the same topic (although slightly different slants) which I’ve now merged. That possibly makes for a little bit of discontinuity in the fabric of space-time (well, at least in the reading of the now merged thread.) Please be sure to QUOTE the material that you’re commenting on, so as to avoid future confusions.
Very well written