When is the solar system going to end?

Answer 1

This depends on what you use as your definition of end. Certainly a dramatic series of events will occur some five billion years from now. At that point the Sun will run out of hydrogen in its core (which it uses as its fuel) and will switch to other types of fuel (e.g. helium, carbon). What exactly happens is quite complex and would take us far into stellar evolution theory; but basically the Sun will swell up and become big enough to engulf the Earth's orbit.

At that point the Earth and the interior planets (Mercury and Venus) will be completely destroyed, although life on Earth will probably have perished some time before that because of increased temperatures.

Eventually the Sun will lose most of its mass through pulsations and the shedding of a planetary nebula (which is just gas and has nothing to do with planets; it is just called that way because the ancient Greeks thought planetary nebula to be distant planets), and become a small star called a white dwarf. This white dwarf is about the same size as the Earth.

The outer planets may survive all this, although life (if any) on them probably won't. In the end the white dwarf will turn into a black dwarf and all that remains of the solar system are a few dead planets orbiting a dark small star.