What is the process that produce energy in stars?

Answer 1

Due to gravity the clouds will start to shrink. In the core density and temperature will become high enough so that nuclear fusion can start. The gas cloud becomes a stable star. This is the present state of our Sun.

Around the Sun a disk of gas and dust is left, containing about 1% of the mass of the Sun. In the inner part of the disk it is warm enough so that molecules like water, ammonia and methane tend to stay as gases and not produce grains and clumps and so on. And because they stay in gas form the radiation pressure from the Sun and the solar wind will push them outwards.

Around the orbit of Jupiter it becomes cold enough for ice to form. The gaseous molecules can produce grains and lumps so there's a lot of this less dense material around to accrete into planets. Jupiter and Saturn grew large enough to pull in great quantities of hydrogen and helium from the solar nebula.

The inner planets accreted from grains containing heavier atoms like oxygen and aluminium and silicon as well as iron and nickel and so on.

Consequently inside the ice limit at 5 AU only small, dense planets have formed, while outside there is matter enough to form the gas giants.

At this stage we have a dozen of proto-planets and quite a lot of comet-like, icy, small stuff. The proto-planets swept space clean with their gravitation fields and the comets rained on them. This also helped in making their orbits more circular.

But it was still a period with big collisions. For instance there are clear indications that the Moon was formed after a collision of the proto-Earth with another big object.

Nowadays, what is left over are zones like the asteroid belt, where Jupiter's perturbing gravity inhibited the formation of another planet. And also the Oort cloud, the region outside the orbit of Neptune, where dwarf planets like Pluto and Eris make their long orbits

Answer 2

The energy production in a star depends on where the star lies in its lifecycle. Our Sun, for example, uses a processes called the proton-proton chain. In a nutshell, the core of the Sun, and other stars below it on the main sequence, is at 10-15 million Kelvin. This allows the smashing of hydrogen protons to create helium and energy.

The other fusion process is the CNO cycle. Four protons fuse, using carbon, nitrogen and oxygen isotopes as a catalyst, to produce one alpha particle, two positrons and two electron neutrinos.

Answer 3

It depends on the type of star and where it is in its life.

The basic process is nuclear fusion, which is colloquially sometimes referred to as "burning" even though it's quite different from ordinary burning.

In most stars for most of their lifetimes, the dominant process is hydrogen burning, where hydrogen-1 is converted into helium-4. This occurs by one of two processes: the proton-proton chain, or the CNO cycle. In stars the mass of the Sun or lower the dominant process is the proton-proton chain reaction. As mass increases, the CNO cycle starts to be the main energy producer.

Objects significantly more massive than Jupiter, but not massive enough to be compress the core to the point where hydrogen fusion starts and they become a star, fuse deuterium (starting at about 12 Jupiter masses) and lithium (starting at around 65 Jupiter masses).

Towards the end of their lives, stars "run out" of hydrogen in the core to fuse and start fusing heavier nuclei (some of this occurs earlier as well, but it doesn't become dominant until the hydrogen in the core is depleted). High mass stars may go though a sequence of helium burning, carbon burning, neon burning, oxygen burning, and finally silicon burning, which proceeds via the alpha process (addition of alpha particles to the nucleus) until nickel-56 is reached.

Answer 4

When a protostar has gathered enough mass, its core collapses in on itself. This collapse causes fusion to kickstart, sending energy from the core out ward.

Answer 5

nuclear fusion

Answer 6

Thermonuclear Fusion*