gen-define-the-hertzsprung-russell-diagram-and-give-one-short-wo-b14f

Define the Hertzsprung-Russell diagram and give one short worked example.

# Hertzsprung-Russell Diagram ## Definition The **Hertzsprung-Russell (H-R) diagram** is a scatter plot that shows the relationship between stars' **absolute magnitude (or luminosity)** and their **temperature (or spectral class/color)**. - **Y-axis**: Absolute magnitude or luminosity (brightness increases upward) - **X-axis**: Temperature or spectral class (temperature *decreases* left to right: O, B, A, F, G, K, M) Stars are not randomly distributed but cluster into distinct regions: - **Main Sequence**: diagonal band (90% of stars, including our Sun) - **Giants and Supergiants**: upper right (cool but luminous) - **White Dwarfs**: lower left (hot but dim) ## Worked Example **Question**: A star has surface temperature 3,000 K and absolute magnitude +10. What type of star is it? **Solution**: 1. **Temperature analysis**: 3,000 K is cool (red), corresponding to spectral class M 2. **Luminosity analysis**: Absolute magnitude +10 is quite faint (remember: higher magnitude = dimmer) 3. **Location on H-R diagram**: - Cool temperature → right side of diagram - Low luminosity → bottom of diagram - Bottom-right region = **white dwarf** zone **Answer**: This is likely a **red dwarf** (low main sequence star) or possibly a **white dwarf**, though 3,000 K would be unusually cool for a white dwarf. Most likely a **red dwarf (M-type main sequence star)**.