Why does nuclear fusion work inside the Sun but not inside Jupiter, which is also made of hydrogen and helium?

Answer 1

Jupiter was never quite large enough for nuclear fusion to start. If it would have been larger it would have started nuclear fusion and become a star.

A little about nuclear fusion and the sun.

The Sun, like most stars, is a main sequence star. This means that it generates its energy by nuclear fusion of hydrogen nuclei into helium and is in a state of hydrostatic balance, neither contracting nor expanding over time. About 3.6×1038 protons (hydrogen nuclei) are converted into helium nuclei every second, releasing energy at the matter-energy conversion rate of 4.3 million tonnes per second, 380 yottawatts (3.8×1026 W) or 9.1×1010 megatons of TNT per second. The rate of nuclear fusion depends strongly on density, so the fusion rate in the core is in a self-correcting equilibrium: a slightly higher rate of fusion would cause the core to heat up more and expand slightly against the weight of the outer layers, reducing the fusion rate and correcting the perturbation; and a slightly lower rate would cause the core to cool and shrink slightly, increasing the fusion rate and again reverting it to its present level.

Answer 2

Because of Jupiter's mass.

Jupiter just doesn't have the mass (or weight) to sustain an ongoing burning nuclear reaction.

The perfect explanation of this is in the book, 2010: A Space Odyessy by Arthur C. Clarke.

Jupiter: The Star that Might Have Been
http://starryskies.com/articles/dln/1-02/jupiter.star.html
Jupiter does radiate about twice as much heat energy as it receives from the Sun, but this heat comes from an internal reservoir left over from the planet's birth some 4.6 billion years ago. The Sun produces it's heat energy through nuclear fusion. The core of the Sun is about 16 million C (29 million F,) so hot that a pinhead would kill a person up to 100 miles away! Jupiter's core is about 33,000 C (54,000 F,) nearly 500 times cooler than the Sun. If Jupiter's composition is so similar to the Sun, then why doesn't it shine like the Sun?

The factor which prevents Jupiter from burning like our Sun is mass. If our king of the planets were about sixty times more massive than it is, it would indeed be a star!. More mass would not make Jupiter grow in size, but rather, cause the planet to collapse from compression under gravity. At this point, thermonuclear reactions would ignite and Jupiter would become a luminous star with a diameter of about 100,000 miles (161,000 km.)

Answer 3

Fusion reactions need the high pressure and temperature in stellar cores to work. Without enough pressure hydrogen atoms still have their electron clouds, which repel each other so other hydrogen nuclei can't get close enough to fuse into helium and release all that energy.

When the mass is great enough, however, two things happen: the atoms are racing around at a higher speed with a better chance of hitting another nucleus, and at high enough temperatures the electrons separate from the nuclei (forming a plasma) anyway, making them easier targets.

Answer 4

One big difference is that the core of jupiter is solid, and probably made of iron and other metals, and the sun has no solid compnents, only plasma.But the real issue is that the sun has reached many billion years ago what uis called a ¨critical mass¨ , an quantity that created enormous amounts of inner pressure, wich elevated the hydrogen pressure and it´s temperature to above a milion degrees centigrade, temeperature necessary for the fusion to happen. Jupiter is to¨cold¨to make fusion work.

Answer 5

Two comments on the above answers.

1) The core of Jupiter is NOT currently known to be solid.

2) Not all stellar fusion cores are hydrogen-helium reactors. All known regularly occuring elements in our universe are the result of stellar fusion. Oxygen is made in stars.

Answer 6

Nuclear fusion of hydrogen requires a temperature of at least 10-million degrees Kelvin. That temperature was reached by our sun billions of years ago strictly due to the immense pressure caused by its mass. Jupiter would need at least 80% more mass for the required pressure to raise its core temperature to 10-million degrees Kelvin.

Answer 7

There is actually some excess heat going out from Jupiter so who knows.

I think that the response is that Jupiter is not massive enough and does not have enough pressure to start the reaction.

We are waiting for the monolith to light Jupiter up.

Answer 8

I believe its mass isn't high enough, it is also too cold, you need temperatures at millions of degrees for nuclear fusion to work as the particles have to be forced together as they are the same charge and would usually repel. Helium is also not required for fusion, it is one of the products of fusion.

Answer 9

Gravity, Jupiter lacks the density and the gravity to start and sustain NF

Answer 10

it does but the reason it does not turn into a star is because it does not have enough mass.But it does produce heat but not heat.And there is not enough helium.