Question about Hertzsprung-Russell-diagram

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SUMMARY

The discussion centers on the relationship between a star's temperature, luminosity, and radius as described by the Stefan-Boltzmann equation. The equation L = σT4 * 4πR2 allows for the calculation of a star's radius (R) when its luminosity (L) and temperature (T) are known. This mathematical relationship simplifies the process of determining stellar radii, making it accessible for those studying astrophysics. Participants express appreciation for the clarity of this concept.

PREREQUISITES
  • Understanding of the Stefan-Boltzmann law
  • Familiarity with stellar luminosity and temperature
  • Basic knowledge of mathematical equations involving area and power
  • Concept of the Hertzsprung-Russell diagram
NEXT STEPS
  • Study the derivation and implications of the Stefan-Boltzmann equation
  • Explore the Hertzsprung-Russell diagram and its applications in stellar classification
  • Investigate the relationship between temperature, color, and spectral classification of stars
  • Learn about the methods used to measure stellar luminosity and temperature
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Astronomy students, astrophysicists, and anyone interested in understanding stellar properties and their implications in the field of astrophysics.

Meerio
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Why can you read out the radii of the stars by knowing their temperature and luminosity?
Can't make sense out of it.
 

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The Stefan-Boltzmann equation tells you the amount of radiation emitted from a unit area of the star as a function of temperature. The total luminosity is then given by just summing this over the surface area of the star, so:

L = \sigma T^4 * 4 \pi R^2

So if you know L and T, you can calculate R.
 
wow that was easy thanks!
 

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