Starstuff

Starstuff

According to the laws of nature two stars of roughly the same mass will evolve in parallel. A more massif star will spend however its nuclear fuel faster and become then a red giant sooner than the other one.

As it is the first to enter the final white dwarf decline. There should therefore be many cases of binary stars at least in our galaxy, one component a red giant, the other a white dwarf, as it is the case!

Some such pairs are very close to each other. The glowing stellar atmosphere flows from the distended red giant to the compact white dwarf. The hydrogen accumulates in this case compressed to higher and higher temperatures and pressures by the intense gravity of the white dwarf, until the stolen atmosphere of the red giant undergoes thermonuclear reactions.

Don’t worry, you’ll stay alive till the end of the days, because you are made of starstuff (quotation and image: © Elena

Then the white dwarf briefly flares into brilliance. Such a binary is called a nova. It has quite a different origin from a supernova, because novae occur only in binary systems and are powered by hydrogen fusion. Supernovae occur in single stars and are powered by silicon fusion.

Red giants find their outer atmospheres blowing away into space as atoms synthesized in the interiors of stars return to the interstellar gas. Thus planetary neubulae are the final stages of Sunlike stars blowing their tops.

Finally, supernovae violently eject much of their stellar mass into space. Hydrogen fuses into helium, helium into carbon, carbon into oxygen and thereafter, in massive stars, by the successive addition of further helium nuclei, neon, magnesium, silicon, sulfur, and so on. Fusion of silicon also generates iron, a pair of silicon atoms, each with twenty-eight protons and neutrons, joining, at a temperature of billions of degrees, to make an atom of iron with fifty-six protons and neutrons.

These are all familiar chemical elements. But stellar nuclear reactions do not readily generate erbium, dysprosium, hafnium, praseodymium or yttrium.

Let’s say that all the elements of the Earth except hydrogen and some helium have been cooked by a kind of stellar alchemy billions of years ago in stars, some of which are today inconspicuous white dwarfs on the other side of the Milky Way Galaxy.

The nitrogen of our DNA, the calcium in our teeth, the iron in our blood, the carbon in our apple pies were made in the interiors of collapsing stars. We are made of starstuff!