Where does the sun start ?Where does the sun finish?

Question

Where does the sun start ?Where does the sun finish?

Answer 1

Where?  Possibly inside a globular cluster, depending on what you mean by "start".  Since the energy/matter ALL started with the Big Bang, we could say that thats the start.  But perhaps you mean after the sun became a proto-stellar nebula?

It finishes up being torn apart as the expansion of the fabric of space time accelerates, prior to that it is a brown dwaft with little energy left to radiate.

As far a dimension, the solar wind extends far out beyond Pluto, so all of the Major planets are enveloped in the Sun.

Answer 2

The sun starts as a proto-star.

A proto-star is born when hydrogen gas in space starts to spin creating a dense center. Once there's enough hydrogen; the dense space becomes so compact that these hyrdrogen atoms start to smash into each other forming helium and thus fusion.

The fusion emits heat and light (or photons). The proto-star then becomes a main-sequence star. The duration of the fuel or energy release by the star depends on how large the star is; our sun is currently half way in it's life cycle. In about 4.5 billion years the sun will then undergo the next stage, the red giant phase. The sun will expand when the hydrogen atoms are no longer.

The red giant will eventually shed layers and form a planetary nebula with a white dwarf star (our now sun) near the middle; the white dwarf will be approximately about the same size of the Earth but will be considerly more dense.

The end or finish of our sun:

The white dwarf will eventually die out and become a black dwarf. So far, we know of no white dwarfs that have entered this stage; it's purely theoretical, but strongly assumed.