# Can we compress any object to create black Holes?

In general, when a star runs out of nuclear fuel, gravity gets the upper hand and the material in the core is compressed even further and creates black holes. I am clear till here.

Now the question is: Does that depend on the mass of the star (or object)?

Naturally, the more massive the core of the star, the greater the force of gravity that compresses the material and easy to create Black Hole. For smaller stars, when the nuclear fuel is exhausted and there are no more nuclear reactions to fight gravity, the repulsive forces among electrons within the star eventually create enough pressure to halt further gravitational collapse. The star then cools and dies peacefully.

In science videos and discussions is said that we can create black holes from any object. For example, if we are able to compress Earth to the size of the tennis ball, can we then create a black hole?

Isn't the nuclear fusion / reaction necessary to create a black hole? Of course, to fight against gravity we may require some kind of energy in this case, Nuclear reactions. But I am generally concerned like, does Nuclear Reaction is only to fight gravity, it does not play any other role in creating Black Hole.

• "Can we" ? Who are you calling a star? Feb 15 '21 at 15:44
• The central black hole of M87 has about the density of air. Dec 6 '21 at 3:02

Do you mean, "Can we in principle", or just, "Can we..." ?

The answer to the latter is no. We have no technology to create black holes. It was a remote possibility that was considered when creating the high energy densities in the LHC, but in practice the energies aren't high enough.

Can we in principle do it? The answer is yes. If you can squash enough mass (or energy) into a very small volume then the inevitable consequence is a black hole.

Most would say that the volume in question is governed by the Schwarzschild radius, $r_s$ which is roughly 3km multiplied by the mass in solar units. Thus for an Earth mass $r_s$ is about 1 cm.

Actually the radius within which collapse to a black hole is inevitable is a little bit larger because even the "hardest" equation of state, where the speed of sound equals the speed of light, cannot resist collapse at radii below about $1.5 r_s$.

The problem is that to compress materials this much would be incredibly difficult. For the example of an Earth mass, we are talking densities of order $10^{30}$ kg/m$^3$. But (long) before you got to that stage, yes you would have the problem of overcoming the nuclear fusion reactions would be initiated that would oppose your compression (ie you would end up making a mini-star before you could get to a black hole). Because the Schwarzschild radius depends linearly on mass, then less massive black holes need to be even denser. However, we are again talking about "in principle". So assuming compression could overcome the various opposing forces, then a black hole could be formed.

It really doesn't matter what the black hole is made of. In a star, the sequence of nuclear fusion events is a consequence of the physical conditions in the stellar interior. It is not anything that is required for black hole formation.

Kind of a quick answer, if you don't mind.

Can we compress any object to create black Holes?

The pressure at the bottom of the ocean is enormous, it would kill a person in a fraction of a second, but it's tiny compared to the pressure in the center of the earth, and that's tiny compared to the pressure in the center of Jupiter, and that's tiny compared to the pressure inside the sun, and the pressure inside of the sun is also, tiny-tiny-tiny compared to the pressure required to create a black hole.

In the science videos and discussions, they say that, we can create Black hole from any object, i mean for example, if we are able to compress EARTH to the size of the Tennis Ball, then we can create Black Hole, Is it True?

I think it's closer to the size of a golf-ball, but yes, that's true. But it's also impossible. There's no known way to do that. We probably don't even have the means to crush a single car to the size of a golf-ball or tennis-ball and if we did, it would just rebound once we removed the compression force. Matter is enormously difficult to crush anywhere close to that much. That's why it only happens in the core of large stars. That's the only place where there's enough pressure.

does Nuclear Reaction is only to fight gravity, it does not play any other role in creating Black Hole.

Nuclear reaction doesn't play a role in creating a black hole. A black hole by definition, is gravity strong enough that the escape velocity is greater than the speed of light. Nuclear energy doesn't come close to that. Nuclear fusion prevents black holes form forming when there's enough matter for a black hole to form, but that's about it. Black holes can't happen without an enormous amount of mass, about 3 solar masses and no sustained nuclear fusion.

Short answer: This is not known to be possible because the only place where there is so much pressure is in the core of an extremely massive star. Also, if the star is too massive the pressure may not be enough, as in the case of stars with 140-250 solar masses. Those stars explode in a pair-instability supernova, or in short, the star explodes, leaving no remnant other than the explosion. After that mass range we go back to black holes.

• Welcome on the Astronomy SE! Afaik the "no remnant" case is a narrow part of the configuration space, it also requires low (or high?) metallicity, too. May 5 '20 at 21:13

Theoretically YES But practically NO. In theory if you can compress any matter to its schwarzschild radius you can create a black hole.

But for now we don't have that technology to compress any object to that extent.

For making a black hole of approximately 2cm radius you have to compress whole earth.