can we say that the sun started its..?

Question

i came to know that the nuclear fusion is going on in the sun making hydrogen to helium. what activity would have initiated this fusion.can we say that the sun started giving light only after this fusion.previous to that what was the sun actually

i do agree that sun is a star.

so is it that our sun was once upon a time an ordinary star without this nuclear fusion.

can we come to the conclusion that all the stars will one day become a sun and some planets may form around them?

Answer 1

It's a good question and some of the others have touched on good points. Let me try to answer without overwhelming you with numbers and big words (accurate though they might have been)

In general, stars are formed when large clouds of hydrogen (a little helium and some trace amounts of other stuff) are influenced by a gravitational force and begin to draw in upon itself. This is a very long process at first, because the dust particles and hydrogen atoms do not have much gravity when they are all spread out as a cloud.

Eventually, though the cloud condenses and starts to take on a spinning (it is spinning because angular momentum is conserved) ball of gas. As it gets more and more dense, the friction of the compression (gravity is much stronger now) causes the ball to heat up.

At some point, the temperatures of these hydrogen atoms gets high enough to ionize the electrons from the nuclei. And a little later, the temperature and the density has those hydrogen nuclei packed so closely that the Strong Nulcear Force (which has a very short range) causes two colliding hydrogen nuclei to merge.

There is a lot more that can be said here, and if you really want to know the play-by-play of the proton proton chain of fusion, I suggest you start another question. But to make a long story short, suffice it to say that fusion occurs.

The energy of fusion has an outward explosive force which opposes that of gravity. This outward force is called "radiation pressure" and it will push outwards against the inward pulling gravitational force until they balance out. That balancing point is called "Hydrostatic Equilibirium".

And that is when the star settles down for the vast majority of its life. The sun has been in that stage for around 4.5 billion years and will stay that way for another 5 billion years or so.

Now to be perfectly clear, it is only when fusion starts that a protostar (ball of hot gas shining from the friction of gravitational compression) is actually a star.

Even so, you are correct in that the sun did radiate light before it became a star (fusion started) Anything that is hot glows, although sometimes it is a frequency of light that we do not see.

Jupiter is a sort of protostar. It never will start fusion on its own, but if it had been a little bit bigger, it might have.
Even so, Jupiter actually emits more energy than it receives from the sun. Much of that energy is in the form of radio waves, though.

Hope that helps and thanks for asking.

Answer 2

No, stars begin to glow before fusion begins, due to gravitational energy. The initial ball of gas must become quite hot (millions of degrees) to begin fusion, and at these temperatures there will certainly be energy emitted. However, the beginning of fusion creates a large increase in energy output.

Gravitational energy is not insignificant though, and astronomers can spot some classes of very young stars by the additional energy output due to gravitational contraction.

Answer 3

In physics, nuclear fusion is the process by which multiple nuclei join together to form a heavier nucleus. It is accompanied by the release or absorption of energy depending on the masses of the nuclei involved. Iron and nickel nuclei have the largest binding energies per nucleon of all nuclei and therefore are the most stable. The fusion of two nuclei lighter than iron or nickel generally releases energy while the fusion of nuclei heavier than them absorbs energy; vice-versa for the reverse process, nuclear fission.

At the center of the Sun, where its density reaches up to 150,000 kg/m3 (150 times the density of water on Earth), thermonuclear reactions (nuclear fusion) convert hydrogen into helium, releasing the energy that keeps the Sun in a state of equilibrium. About 8.9 ×1037 protons (hydrogen nuclei) are converted into helium nuclei every second, releasing energy at the matter-energy conversion rate of 4.26 million tonnes per second, 383 yottawatts (383 ×1024 W) or 9.15 ×1010 megatons of TNT per second. 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 shrink slightly, increasing the fusion rate and again reverting it to its present level.

Answer 4

No No No.............the sun is still a star. its just a few planets came into its path and are now orbiting it. the sun will always be a star until it reaches its death. All the other stars will stay stars forever and if they get planets orbiting them then that will be a seporate solar system altogether.
if you have any more questins email me for a real answer.

Answer 5

The pressure of the star falling in on itself.