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Stars & Stellar Evolution

How stars are born from cold clouds of gas, how they burn for millions or billions of years, and how they die — sometimes as quiet white dwarfs, sometimes as black holes. The physics behind every point of light.

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The HR Diagram: The Single Most Useful Chart in Astronomy

The Hertzsprung–Russell diagram plots stars by luminosity and temperature. Nearly every question in stellar astronomy starts here.

Dmitry Shteynbuk · March 12, 2026 · 3 min read

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Terms to know

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HR diagram
The Hertzsprung–Russell diagram: luminosity plotted against temperature.
Main sequence
The diagonal band on the HR diagram where stars spend most of their lives fusing hydrogen.
White dwarf
The exposed carbon-oxygen core left after a Sun-like star sheds its outer layers.
Neutron star
The compact remnant of a massive star's core collapse.
Black hole
A region where gravity is strong enough that not even light escapes.
Parallax
The apparent shift of a nearby star against the background as Earth orbits the Sun.

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