What must the inward and outward forces within the sun be in order for the sun to be stable?

Answer 1

If the forces on a planet were balanced, the planet would move in a straight line, not in an orbit.

The force on a planet that keeps it in a closed orbit, and is not balanced by any other force, is

the force of gravitation between the planet and the sun.

Answer 2

For the Sun to be stable, the inward force of gravity must be balanced by the outward force of radiation pressure caused by nuclear fusion reactions in its core. These forces must be in equilibrium to maintain the Sun's shape and prevent collapse or expansion.

Answer 3

The sun has massive gravity, and it is gravity that is attempting to pull all the material in the sun into a tiny ball. But the massive amount of thermal energy generated by all the nuclear fusion reactions that are occurring in our local star are attempting to force all the material outward. It is this "standoff" between gravity and fusion-generated thermal energy that set the hydrostatic equilibrium of the sun.

Answer 4

Mass, which is a measure of the amount of matter in an object, is affected by the force of gravity.

That would tend to keep the nebula from flying apart.

The collapse of the nebula could be prevented by the motion of the particles in the nebula, causing centrifugal effects. This is sometimes called the "centrifugal force".

(The question probably meant "collapsing or flying apart".)

Answer 5

Pressure and gravity are the two forces at work in a nebula.

We understand that a nebula is a cloud composed of gases and dust. And when we recall that gasses expand if not contained, we will understand the internal gas pressure pushing outward. This pressure will be acting against the attractive force of gravity that is characteristic of all matter, including gasses and dust. It's gas pressure versus gravity, which is a common theme in cosmology.

Answer 6

The outward force of the internal nuclear explosions in the core of the star try to push the material away from the continual explosions. This is balanced by the intense gravity of the star's mass which is trying to crush the star to a point.

Answer 7

Nuclear Fusion and Gravity. _________________________ The nuclear fusion provides heat and energy, which tries to cause the star to expand. It is, after all, a nuclear bomb going off thousands of times each second, and it ought o blast itself to pieces.

Gravity, on the other hand, tries to pull all matter in to itself. Without nuclear fusion, the gravity of the star would crush its mass into degenerate matter, without the normal space in between the protons and electrons.

These two forces, working in opposition, keep the star stable. As long as the star has hydrogen fuel, it will remain in balance. But when the hydrogen fuel begins to run low, then all hell will break loose; the nuclear fire will not have enough energy to keep the Sun from starting to collapse.

But the collapse itself will set off the next phase of growth! The intense gravitational pressure will cause a corresponding increase in the temperature of the core of the star. At 15 million degrees, hydrogen fuses into helium. But as the hydrogen is depleted and the star begins to collapse, the temperature continues to rise because of gravity. And at about 35 million degrees, the helium which is now so prevalent in the star's core will begin to fuse into carbon and oxygen, releasing vastly MORE heat and power, and causing the star to expand hundreds or thousands of times, becoming a red giant.

Answer 8

A nebula only collapses if the gravitational forces overcome the forces associated with gas pressure.

(Layman's example:)

For instance, a liter of water fits in about a liter - but if you'd boil the entire liter of water into a gas, it would take up a lot more space because the energy you added made the water molecules move very rapidly.

Gravity, a very weak force between matter, has to at the very least be stronger than this force or the nebula will not become more compact.

Furthermore, nebula with only very light materials (such as Helium) are not very capable of radiating heat into space, and because a gas becomes hotter when you compact it more, gravity essentially tries to make the gas more dense, heats it up, so it becomes less dense.

So the nebula just 'hangs' there, and does nothing until the gravitational forces are strong enough (or in this example the nebula can radiate heat more efficiently, by for instance being infused by heavier atoms such as Iron from a nearby supernova - which are better at radiating heat).

~ Anon666

Answer 9

The internal pressure of the star, and the 20 million degree heat, cause the star to expand. The massive gravity of the star causes it to collapse.

As long as the Sun's nuclear fusion reaction is going on, it will maintain that balance. About 4 or 5 billion years from now, the Sun's hydrogen fuel will begin to run out, and it will start to collapse. The increasing pressure from the collapse will also increase the temperature, and when it reaches about 100 million degrees, the helium of the Sun will start fusing, causing the Sun to expand into a red giant.

After a few billion more years, the Sun will slowly collapse again into a white dwarf star.

Answer 10

The force of gravity from the Sun's mass causes the Sun to contract; the power and heat generated by the hydrogen fusion reaction at the Sun's core causes the Sun to expand. These two forces are in balance; otherwise, the Sun would be compressed to the point where the heat of fusion DID equal the compressive force of gravity.