Stars about the size of our sun go through the same first four stages as does any other star. They begin their lives as a nebula, then become a Protostar, eventually becoming a main sequence star and finally a red giant.

These three pieces of evidence, 1) stellar evolu- tion theory, 2) expanding OB associations and 3) the interstellar medium, constitute three basic “proofs” of ongoing star formation in the Milky Way.

The exact stages of evolutions are: Subgiant Branch (SGB) – hydrogen shell burning – outer layers swell. Red Giant Branch – helium ash core compresses – increased hydrogen shell burning. First Dredge Up – expanding atmosphere cools star – stirs carbon, nitrogen and oxygen upward – star heats up.

Low mass stars (stars with masses less than half the mass of the Sun) are the smallest, coolest and dimmest Main Sequence stars and orange, red or brown in colour. Low mass stars use up their hydrogen fuel very slowly and consequently have long lives.

For low-mass stars (left hand side), after the helium has fused into carbon, the core collapses again. As the core collapses, the outer layers of the star are expelled. A planetary nebula is formed by the outer layers. The core remains as a white dwarf and eventually cools to become a black dwarf.

While the sun will spend about 10 billion years on the main sequence, a star 10 times as massive will stick around for only 20 million years. A red dwarf, which is half as massive as the sun, can last 80 to 100 billion years, which is far longer than the universe’s age of 13.8 billion years.

The formation and life cycle of stars

• A nebula. A star forms from massive clouds of dust and gas in space, also known as a nebula.
• Protostar. As the mass falls together it gets hot.
• Main sequence star.
• Red giant star.
• White dwarf.
• Supernova.
• Neutron star or black hole.

A planetary nebula is the final stage of a Sun-like star. As such, planetary nebulas allow us a glimpse into the future of our own solar system. A star like our Sun will, at the end of its life, transform into a red giant. Stars are sustained by the nuclear fusion that occurs in their core, which creates energy.

about 4.5 billion years

In either case, an exploding Moon, by natural means at least, is pretty unlikely for now. That leaves artificial methods — probably some kind of enormous bomb. It is not impossible to blow up the Moon with a bomb, but it would be a massive job (a single nuke isn’t going to cut it, you’d need millions).

The universe will die. Eventually it will become nothing. In roughly a quadrillion years, a last star will give its last twinkle, and black holes will devour everything before they completely evaporate. And in a googol years (that’s 10 to the hundredth power, which is a lot), the universe will be empty.

The trace signals from the explosion that set the universe in motion 13.7 billion years ago will likely be all gone 1 trillion years from now, the researchers said. (In fact, by that time, our own Milky Way galaxy will have collided with its neighbor, Andromeda, to create the Milkomeda galaxy.)

I think a quintillion years are a billion billion years, so we are looking at 31.7 billion years. That’ll be 31,700,000,000 years.