# How can a star turn into a black hole, with the law of conservation of mass?

• ilikefun411
In summary, black holes have a mass that is either the same or less than the star that collapsed into it. If there is a nova event during the collapse, most of the mass will be scattered into space, while the remaining mass will form the black hole. Black holes have immense gravitational fields and act like stars or planets from far away. However, the closer you get to a black hole, the more its gravity behaves strangely. This is because gravity is proportional to the distance from the center of an object squared. While the mass/energy remains the same, it may not all be in the form of particles of matter. This concept can also be referred to as the law of conservation of mass or energy.
ilikefun411
where does all the mass go?

Astronomy news on Phys.org
Black holes have a mass that is the same or less then the mass of the star that collapsed into the black hole. If there is a nova event connected to the collapase, most of the mass will be scattered into space, if the remaining mass is large enough then it will collapase into a black hole.

It should be noted that black stars don't have an immense gravitational field. From far away, a black hole acts just like a star, or a planet. It's only when you get really close to a black hole that the gravity starts acting strange... because gravity is proportional to the distance from the center of an object squared, if you're, say, standing on the surface of the earth, you're 4,000 miles from the center of the earth. A black hole with the mass of earth, however, may have a radius of 4 miles. So if you're 10,000,000 miles away from earth, it has the same gravitational pull as if you're 10,000,000 miles away from the black hole. But if you're 1 mile above the surface of the earth, you're 4001 miles away from the center. If you're 1 mile above the surface of the black hole with the same mass, you're 5 miles from the center

ilikefun411 said:
where does all the mass go?
I haven't heard of "conservation of mass", only conservation of energy. But, since mass = energy (e=mc2) I guess it could be called either.(?)

A BH can form from several methods; direct collapse of a massive star, large core remaining from a Type II supernova, merger of two massive bodies etc. Any BH formation mechanism causes some mass loss and since mass = energy, some "mass loss" is carried away as EM radiation, gravitational radiation and sometimes conversion of angular momentum.

So, mass/energy will actually remain at the same total, just not all as "particles of matter".

for conservation of mass, replace energy with mass in the law of conservation of energy. it's the same thing, like you said.

## 1. How can a star turn into a black hole?

When a massive star runs out of nuclear fuel, it can no longer produce enough energy to counteract its own gravity. The core of the star collapses inward, and the outer layers are violently expelled in a supernova explosion. If the remaining core is at least three times the mass of the sun, its gravity becomes so strong that it can trap even light. This results in the formation of a black hole.

## 2. What is the law of conservation of mass?

The law of conservation of mass, also known as the law of conservation of matter, states that mass cannot be created or destroyed in a chemical reaction or a physical transformation. This means that the total mass of the reactants in a reaction must equal the total mass of the products.

## 3. How does the law of conservation of mass apply to the formation of a black hole?

The law of conservation of mass applies to the formation of a black hole because even though the star's mass is increasing during the collapse, the total mass of the system remains the same. The mass is simply concentrated in a smaller volume, resulting in a higher density and stronger gravitational pull.

## 4. Can a star of any size turn into a black hole?

No, only stars with a mass of at least three times that of the sun can turn into black holes. This is because the star needs to have enough mass to overcome the repulsive force of electron degeneracy pressure and the gravitational force of its own mass.

## 5. Is it possible for a black hole to lose mass and violate the law of conservation of mass?

According to the law of conservation of mass, mass cannot be created or destroyed. However, black holes can lose mass through the process of Hawking radiation, which is the emission of particles from the black hole's event horizon. This does not violate the law of conservation of mass, as the mass is not being created or destroyed, but rather converted into energy.

Replies
11
Views
992
Replies
6
Views
1K
Replies
5
Views
2K
Replies
13
Views
1K
Replies
10
Views
1K
Replies
11
Views
2K
Replies
5
Views
2K
Replies
4
Views
2K
Replies
1
Views
1K
Replies
1
Views
1K