Stimatore Hertzsprung-Russell
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Luminosita (L_sun)
1.0000 L_sun
Luminosity (L_sun) vs Effective Temperature
Formula
## The Hertzsprung-Russell Diagram The HR diagram plots stellar luminosity against temperature. For main-sequence stars, hotter stars are larger and more luminous. ### Empirical Approximation Radius: **R / R_sun ≈ (T / T_sun)^0.8** Luminosity from Stefan-Boltzmann: **L / L_sun = (R/R_sun)² × (T/T_sun)⁴** These are rough main-sequence estimates. Giants, supergiants, and white dwarfs fall off the main sequence.
Esempio Risolto
A star with T = 10 000 K (A-type).
- 01T/T_sun = 10000/5778 = 1.731
- 02R/R_sun ≈ 1.731^0.8 ≈ 1.562
- 03L/L_sun = 1.562² × 1.731⁴ = 2.440 × 8.975 ≈ 21.9
- 04About 22 solar luminosities.
Domande Frequenti
What is the main sequence?
A band on the HR diagram where stars fuse hydrogen in their cores. About 90% of all stars lie on it. Stars spend most of their lives here.
Where do red giants appear?
Above and to the right of the main sequence: cool but very luminous because of their enormous size.
Where do white dwarfs appear?
Below and to the left: hot but very faint because they are tiny (roughly Earth-sized).