Celebrate All Scientists: Chushiro Hayashi

Celebrate All Scientists

Today, LSC celebrates the work of astrophysicist Chushiro Hayashi on the 102nd anniversary of his birthday!

Hayashi was a Japanese astrophysicist whose work led to our modern understanding of the early life of a star.

Stars form when a nebula, which is mostly hydrogen gas floating in space, contracts due to gravity. Over time, the proto-star builds up more and more gas, until finally the pressure is high enough that it begins a process called nuclear fusion. That's when it becomes a proper star, because nuclear fusion creates the light we see from a star.

But that's not the whole story. There's a period when small stars have just formed, before they begin burning hydrogen, but when they're already producing light. This is called the “pre-main sequence” phase. In this phase of the star's life, the star is contracting; it heats up as it contracts, causing it to light up and become visible, before it starts burning its hydrogen.

Hayashi's work led to our understanding of this phase. Because of this, the small stars that develop this way are said to follow the “Hayashi track” rather than the “main sequence” of development that most stars follow.

Besides this monumental contribution to our understanding of stars, Hayashi discovered a limit to how big a star can get, depending on its mass, which is called the Hayashi Limit. He also contributed to our understanding of how elements were formed in the Big Bang.

Hayashi’s work greatly improved scientific understanding of the universe!

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