Stardust

"Star Birth" Clouds in M16 (NASA)
"Star Birth" Clouds in M16 (NASA)

If you ask an astrophysicist what is the most beautiful thing about science, a lot of them will answer; we are all made of stardust. Literally.

A star starts out in gas clouds mostly in the spiral arms of galaxies. Dense regions start collapsing in on themselves to form protostars. The protostars keep collapsing which forms ever denser regions which continues until the very core starts burning hydrogen into helium. It also gathers more weight and starts exerting a gravitational effect on the heavenly bodies around itself. And thus, literally, a star is born.

That star, once formed, is on a one way trip toward extinction. Sure, it will take millions of years, but it is inevitable. First it will burn hydrogen into helium. That lasts something like 10 billion years. Then, when there is enough helium, it will start burning helium into carbon. If it’s a regular star, it will pretty much just fizzle out into a white dwarf and die around this time. But, for the purposes of this discussion, that star is a high-mass star around ten times bigger than the sun we know and love.

NASA/ESA, The Hubble Key Project Team and The High-Z Supernova Search Team
NASA/ESA, The Hubble Key Project Team and The High-Z Supernova Search Team

In a high-mass star when the helium in the core runs out the nuclear reaction in the core just keeps on going, turning the carbon in the core into oxygen, neon, sulfur and eventually into iron. The iron, being the most stable nuclear substance, no longer reacts but still keeps contracting in on itself. Once it reaches such density that it will no longer contract things really start going off their hinges. The rest of the matter trying to cascade into the core will start bouncing off and turns into a supernova explosion. For a whole month that star will burn brighter than all the others in the galaxy put together. During that time it will exhaust all manner of elements into interstellar space. Without the fiery death of a star, life would be impossible.

And what happens to the core? That again, depends on the size of the star. If it happens that the star was initially only about ten times the size of our sun, the core will cool down and form a neutron star (which in itself is a concept too large to discuss here and so we’ll return to it another time). If, however, our star is even bigger than that it will simple keep on collapsing in upon itself eventually forming a black hole.

Finally, I’m going to leave you in the utterly capable hands of Neil deGrasse Tyson, who manages to express everything I just said in a sound bite sized piece.

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