Luminosity

Definition

Luminosity is the total amount of energy a star emits per unit of time, measured in watts. It depends on both the star's temperature and radius.

5 Must Know Facts For Your Next Test

1. Luminosity is different from apparent brightness, which is how bright a star appears from Earth.
2. The formula to calculate luminosity involves the Stefan-Boltzmann law: L = 4πR²σT⁴, where R is the radius and T is the temperature.
3. Stars with higher temperatures and larger radii have greater luminosities.
4. Luminosity can be compared using the Sun as a reference unit called solar luminosity (L☉).
5. Hertzsprung-Russell (H-R) diagrams plot stars based on their luminosities and temperatures.

Review Questions

• What factors determine a star's luminosity?
• How does luminosity differ from apparent brightness?
• What does an H-R diagram show in terms of stellar properties?

Related terms

ApparentBrightness: The observed brightness of a star from Earth, affected by distance and interstellar dust.

StefanBoltzmannLaw: A principle stating that the energy radiated by a blackbody per unit area is proportional to the fourth power of its temperature.

HertzsprungRussellDiagram: A graph plotting stars' luminosities against their temperatures, revealing patterns among different types of stars.