So there you are. I’d say somewhere between 25 pounds and 1 ton give them a call. Foil is a bit more dense than plastic wrap, so I’d think you’d need 100 pounds or better of the stuff to impress anyone there.
Someone was working on a foil ball for years, but no updates since '98:
I should have been a little more weasly with my “so far as we know”. Quark stars do seem to be a theoretical possibility (though nobody would be surprised if the theory turned out to be wrong), and we’ve seen some things which look like they might be quark stars, but there’s no really solid evidence for them yet. But in any event, there’s a very narrow window of initial conditions (mostly mass) which will get you a quark star.
As I think about this some more, by the way: You will probably get fusion before you collapse to a balck hole, but since aluminum won’t fuse as efficiently as hydrogen or helium, you’re going to get to the neutron star stage at least as easily, or more so, than you would with a normal star. And once you have a neutron star, it doesn’t matter what material you started with. I still don’t want to do the calculations, but in this case, I don’t need to, since Chandrasekar already did them for me. So, three solar masses is the limit before it turns into a black hole.
Thinking about this yet more, though, that’s still not the answer we want. Sure, a black hole isn’t a ball of aluminum any more, but then again, neither is a neutron star. If we’re going to disqualify a black hole, then the cutoff we really want it the threshold for fusion ignition, because that’s when it starts being not aluminum.
Ok, I am not a nuclear physicist, but: as Chronos said
I didn’t know about the alpha capture mechanism that Achernar mentioned, but presumably if conditions are extreme enough to crunch matter to the neutron degeneracy stage, you have reached the point where anything lighter than iron will fuse. What I don’t know is if there would be a distinct “aluminum fusion” stage, or if it would be concurrent with the collapse of the aluminum into neutronium.
Aluminum has an atomic number of 13, and iron conveniently enough is 26, so two aluminum nuclei have exactly enough protons to make one iron nucleus. The only hitch is that there aren’t enough neutrons; aluminum-27 and iron-56 are the most stable isotopes respectively, so you’re two neutrons short of being able to have direct fusion.
I do know that if you collapsed aluminum into neutronium, there would be a very large energy release representing the average difference in binding energy between aluminum and iron. You might have a core of neutronium, with a very hot shell of aluminum undergoing collapse onto the core, similar to a red giant situation (hydrogen fusing onto a helium core), only much, much hotter and denser.
Assuming a quark star is a possibility does your post mean that a neutron star can go directly to a black hole or must it pass through the quark star step on the way down to a black hole?
I am by no means an expert, but according to the various general interest books I have read, there is no minimum mass required to create a black hole. In fact some theories indicate that the universe used to be filled with micro black holes created during the big bang wizzing around the universe while slowly evaporating.
But to get to my original point, one book I have says that a black hole weighing as much as the earth would be 1/3 of an inch in diameter.
Of course it isn’t going to get that way on its own. It requires considerable pressure. It would probably take at least two of the office workers falling on the ding-dong ball to compress it enough to turn it into a black hole.
You’re correct, however, we are discussing the necessary mass to create a black hole purely from the gravitational collapse of a slowly-growing body. And that’s 3.2 solar masses of material, disregarding heating efects due to fusion, and other similar factors. If you compress a golf ball enough, you can turn it into a very tiny black hole, but that’s not quite what the OP is asking about.
There are certainly cases where you can bypass the quark star stage, if you add enough mass at once. Collide two neutron stars together, and you’ll get a black hole. But if we’re slowly adding mass… I don’t know. But I think that you’d probably get a quark star (if they exist) between the neutron and hole stages.
Great first post, rbroome, and you’re correct on the size of an Earth-mass black hole. Except that there’s no known way in the current Universe to produce a hole that small. But then, what do theoretical physicists care about silly little details like that ;)?