Question.

How long will a typical class II (G) star (like our sun) stay on the main sequence before exhausting its fusionable fuel and imploding into a dwarf star, leaving an expanding ring of gas called a planetary nebula, or else going supernova, which will make the star shine for a few days or weeks as bright as the rest of its home galaxy combined, creating the heavier elements up to uranium in the process with which it will then seed dust clouds and pave the way for second and third generation stars, meanwhile leaving its own leftover core of matter in a very bad state, collapsing into either an 'ordinary' neutron star, denser varieties of neutron stars called pulsars or magnetars, or giving up completely and falling into a single point around which a black hole is said to have formed (defined by the Schwartzschild radius and not approachable any closer than its event horizon - which has a radius derived solely from the mass of the collapsed core)? And are there any tricks or assumptions in this question, beyond the main answer, which seem objectionable to you? Open floor, anyone.