LearnStars & evolutionBuilds on the rest
The Hertzsprung–Russell diagram
A plot of luminosity against temperature on which stars fall into a few narrow bands rather than scattering at random.
Why it matters
Its structure is the whole of stellar evolution in one picture: the main sequence is where stars spend most of their lives, and everything off it is a star in transition.
Rests on
- Spectral classificationThe sequence O B A F G K M, ordering stars from hottest and bluest to coolest and reddest by the lines in their spectra.
- Blackbody radiationThe characteristic spectrum any warm, opaque object emits, whose shape depends only on its temperature.
- The magnitude scaleA logarithmic, backwards brightness scale in which smaller numbers are brighter and five magnitudes is a factor of exactly 100.
6 concepts in the full chain back to first principles.
Leads to
Nothing here builds on it yet.