Please help if you want to or can

Question

What is the source of the heat produced by the Sun? How long (approximately) will the Sun maintain the current levels of heat and brightness? What is likely to happen afterwards? What is likely to happen to Earth as the Sun evolves?

What is the "main sequence?"

Name the possible ways a star can evolve after the main sequence.

Answer 1

Nuclear fusion.

Four to five billion years

It will expand as it fuses the last of its core hydrogen. The outer layers of gas will swallow some inner planets.  Then the inner parts of the Sun will stop fusing, contract, and become a white dwarf. It will remain a small, hot, slowly- cooling dwarf for many tens of billions of years after that. It will have most of the heat of a full-sized star, but only a tiny surface area with which to radiate it. Therefore, it will take a very long time to cool down.

it will be too cold to support life on Earth by then, even if the Earth could survive the red giant phase.

During most of the lifetime of a star, the interior heat and radiation is provided by nuclear reactions near the center. this phase of the star's life is called the main sequence.

after the main sequence, most of the nuclear fuel in the center has been used up. The star now requires a series of less efficient nuclear reactions for internal heat, before finally collapsing when these no longer generate sufficient heat to support the star against its own gravity.

Answer 2

the sun is basically a large ball of hydrogen;  at some point, due to gravity, the pressure and temperture grew to the point that the it began to fuse the hydrogen into helium.   So, billions of times a second, the sun takes 4 hydrogen atoms and fuses them together to form 1 helium atom.

The sun has enough fuel for about another 5 billion years... when the fuel runs out, the sun will swell, and become a Red Giant. During this phase, the solar atmosphere will expand past the orbits of Mercury, Venus, and Earth, and those 3 planets will slowly, due to atmospheric friction with the sun, spiral in until they join with the Sun's core.

Then, after the sun has blasted off it's outter layers, it'll be a small "white dwarf" - really just the core of the sun, quite dead - and will slowly cool over millions of years, until it becomes just a dark cinder.

Our sun is quite small, and not very massive.  Stars with masses 3 to 8 times larger than the sun can "implode" - once the fusion stops in their cores, the energy keeping the star "inflated" is gone, and the surface comes crashing in on the core.  The sudden over-pressure creates a huge explosion called a Super Nova.  The exposion blows off massive amounts of stellar material, and compresses the core of the star - sometimes, it compresses it so much, that the electrons and protons in atoms are crushed into each other, forming a mass of nothing but neutrons.  This is a "Neutron star" - they're quite mall - 10 to 20 miles across, and dense.  A teaspoon of it's material would weigh more than Mt. Everest.

If the star is more massive, then the collapse may not stop at the Neutron star stage - it may continue until space itself cannot support such a great mass in such a small space - and a black hole is formed. It's basically a dimensionless point in space-time.  The only indication of it's mass is how large the "Event Horizon" around it is... the Event Horizon is the border where normal space stops, and where the realm of the black hole begins.  The speed needed to escape a black hole's gravity within the event horizon is greater than the speed of light - which is impossible (at least, in our universe).  

Answer 3

nuclear fusion creates the heat

and the sun will start to bloat (and get hotter) in about 4-5 billion years

as i said before, the sun bloats up, to huge proportions, it will consume mercury and venus, by completely 'eating' their orbits...

what happens to the earth afterwards is debatable... some say the earth will be consumed as well, others say the suns gravity (and since it's final bloat size is so near our orbit) will push earth just beyond inceneration range.

dunno the other two off the top of my head.

Answer 4

Click on this link, all your answers are there.

http://en.wikipedia.org/wiki/Sun