an old star of average size that has begun to run out?

Answer 1

jrleite01's answer is close though a little misleading.
A star like the sun gets hotter and brighter as it ages. And at some point, when the hydrogen in the sun's core starts to run out, it begins its death phase.
The sun (and all stars) spend most of thier life in a state of hydrostatic equilibrium in which the crushing contraction of gravity is balanced by the energy produced by fusion in the star's core. But when the fuel for that fusion starts to run out, the gravity is still present and there and continues to try to crush the star down onto itself. This causes the temperature in the core to increase dramatically and the core expands to include even more hydrogen from the area that was previously outside the core. (You see not all hydrogen in a star gets converted to helium by fusion. Only the hydrogen in the core does because that is the only place where the temperature is hot enough to sustain fusion.) Now when this convulsion happens (gravity squeezes, temperature goes up higher) then the core gets hotter and not only does it expand to include more hydrogen, but at this point the temperature gets hot enough to start fusing helium. The amount of energy coming from the core is now much greater and so the star expands and becomes truely huge. This is the red giant phase and in a star like the sun, it will swell up to engulf both Mercury and Venus and possibly even the earth itself.
This goes on until once again the amount of hydrogen in the core starts to run out. Then the whole thing repeats itself.
The cycle goes on until at some point the crushing effect of gravity can not generate temperatures hight enough to fuse the material in the core (probably carbon, nitrogen and oxygen by now) into something heavier. Then there will be a final crushing effect. The temperatures will not ignite the fusion of the heavier elements, but it will be enough to cause the outer layers of the sun to "puff" off (not explode). It will almost look like a big smoke ring.
Those outer layers will drift off into the universe (a planetary nebula) to mix with gas and dust from other nebulae and maybe be part of a new star billions of years later.
All that will remain fo the now dead star will be it's exposed core. There will be no fusion. But it will still be hot for a long time. This is the white dwarf. It will slowly cool and eventually become a black dwarf that will have very strong gravity, but not strong enough to be a neutron star or black hole.

Answer 2

well if ur saying like our sun, it starts to grow and grow, because the hydrogen is ruining out and the star is expanding, then it start pulsing like a heart beat , Lots and lots of energy is released and eventually the sun explodes and all there is left is a object mearly the size of earth glowing white, called while dwarf

Answer 3

this is normal
all stars eventually burn out.