Getting Frugal with the Sun

How long is the Sun going to last? According to our best understanding of astrophysics today, the total lifespan should be around 12 billion years, of which we have arrived at about the halfway point.

But what if we built a Dyson sphere? Could we extend the life of the Sun indefinately? One astronomer thinks so:

So just how much energy is available? If all the Sun’s mass converted to energy at current output it would last 14.5 trillion years. But it’s a giant fusion reactor instead. Proton-proton fusion, and associated reactions, convert 0.7% of the mass into energy. As the Sun is currently 74% hydrogen, proton-proton fusion would last 75 billion years using all the hydrogen. If we ignited helium fusion after that we might get another 30 billion years.

Some of the energy involved in the Sun’s evolution is from gravitational collapse. About half the Sun’s mass will collapse into a white dwarf liberating a few billion years worth. If the Sun could be collapsed further then even more would be liberated. The absolute limit is, of course, when the Schwarzschild radius is reached and we’ve made a black hole. If we collapsed the Sun into a quark-star just 6 km in radius we might extra a few trillion years of energy out of it.

Via reverse baryogenesis we might then extract all the mass-energy out of the remaining quark mass, thus getting the full 14.5 trillion years. All up we might extract 20 trillion years out of the Sun. But what happens then?

It's an interesting article, here.

The exactly, polar opposite is here.