Why does it take a star billions of years to fuse all it's Hydrogen into Helium?

Question

Why not all in a few seconds like an H-bomb?

Answer 1

The fusion reaction rate depends on temperature and pressure. The conditions required for fusion to occur are only present in the core of a star. The larger the star, the larger, hotter, and denser the active region, and the faster the star uses up its fuel. There's a theoretical limit to star size, around 120 solar masses, I think, though it varies with the purity of the hydrogen. Above this size limit, a star will indeed blow itself apart as soon as fusion begins.

Answer 2

Because there's just so much Hydrogen to burn in a star. The sun is 1.9891×10^30 kg (332,950 Earths) -that's a whole lot more hydrogen than in an H-Bomb which is just a couple kilograms of hydrogen (if that).

Also once the star done burning all its Hydrogen, a star will collapse in on itself and start fusing the helium into heavier elements and if its big enough it will fuse those heavier elements into even heavier elements.

Answer 3

The solar won't be able to bypass on invariably. at the same time as all the hydrogen has been fused into Helium, the solar will substitute fairly and commence to fuse the helium nuclei. this does no longer launch as a lot ability because the fusion of hydrogen, besides the undeniable fact that. this can proceed by ability of different aspects till the in straightforward words ingredient left is gaseous iron, and the solar ultimately dies. do not problem about that, besides the undeniable fact that, our solar has yet another reliable 5 billion years left in the previous it dies! The solar will go by ability of a substitute of sorts in the previous it is going out. it is going to change right into a red large on the top of its existence. as quickly because it has almost depleted it hydrogen and starts burning the helium byproduct that that's been storing for billions of years, it is going to improve to easily about 256 situations its present day radius. That boost could take about 5 million years to finish.

Answer 4

To fuse, two hydrogen nuclei have to crash into each other at high speed. Even at the temperatures and pressures in the core of the sun, most nuclei simply miss colliding with all the others. But since the Sun is so huge, enough collisions do take place each second to make enough energy to keep the Sun shining. By the way, the Sun fuses as much hydrogen and makes as much energy as BILLIONS of thermonuclear weapons every SECOND!

Answer 5

H-bomb only fuses a very small amount of hydrogen into helium


it has to do with the "positioning" of the nuclei in close proximity
under apropriate conditions.

If you set off an H-bomb on the surface of the sun,
nobody would notice .... it is an infinitesimal amout
of fusion-reaction in the "REAL WORLD" of stellar
mechanics.

Answer 6

Because it is only at the core (a small % of the bulk of the star) that the added pressure makes it reach the needed temperature for fusion. The rest of the star, most of it, is only there as some sort of blanket, and is not fusing.

Answer 7

The Earth is about 13 thousand kilometers (8000 miles) wide, whereas the Sun is roughly 1.4 million kilometers (900,000 miles) across. This means it would take more than 100 Earths to span the width of the Sun! If the Sun were a hollow ball, you could fit about one million Earths inside of it!
A hydrogen atom is approximatly 0.12nm (nanometers) in size. I'm going to round it to 0.10nm, so there are 10 hydrogen atoms per nanometer.
one meter = 1,000,000,000 nanometers, so there are 10,000,000,000 hydrogen atoms per meter.
1 Kilometer = 1000 meters, so there are 10,000,000,000,000 hydrogen atoms per kilometer
the Sun is 1,400,000 km in diameter, which makes the volume of the sun 58,893,870 cubic kilometers, which means that there are approximately
588,938,700,000,000,000,000 hydrogen atoms in the sun (if my calculations are correct, it's entirely possible I'm wrong) That is a LOT of hydrogen to fuse.

Answer 8

Fusion reaction gives off so much energy that it seems though the whole star should undergo fusion quickly, but in reality, there is so much fuel in this star that it takes years of high pressure and heat to convert all of it.

Answer 9

Now and then they do. The reasons are unclear. Then they are called Novas or Supernovas. But those are fairly rare events.

Answer 10

because the pressure valve is stuck on low