Quirks & Quarks

How is it possible in the vastness of space that our sun ever had the density of gasses needed to form a star?

Dr. Jesse Rogerson goes way back to the very first fraction of a second after the Big Bang for the answer.
The Sun's gases were only dense enough to form a star only after gravity could work. (Pixabay)

Greg Burke in Ottawa asks: "How is it possible in the vastness of space that our sun ever had the density of gasses required to form a star?"

At its base, the question is why all the matter didn't just spread out in the universe, but rather collapsed into dense areas like stars, galaxies and — eventually — us.

Dr. Jesse Rogerson, science advisor with the Canada Aviation and Space Museum in Ottawa, went back to the very first fraction of a second after the Big Bang for the answer. 

Way back then, the rules of the universe were completely different. They were on a quantum scale.

"There's this weird rule that says the universe can play with the energy density on small scales for short periods of time," Rogerson says. "In the first fraction of a second, there was some bubbling happening. It wasn't perfectly uniform. That's the first piece."

Gravity takes over

The second piece is cosmic inflation — the principle in cosmology that there were massive amounts of inflation where the universe went from smaller than a proton at the beginning to the size of basketball in a super-short amount of time.

Rogerson says it happened quickly enough to take those initial, microscopic quantum fluctuations or "bubbling" and stretch them out to a macro scales where energy density was hotter in some places and cooler in others. 

Those fluctuations or imperfections in the early universe became stuff. 

"That creates denser regions and eventually gravity takes over and pulls everything together and makes stars, people and you and me."

Once gravity could work, ta-da: so could matter.