1. What is Star Luminosity?

Star luminosity is the total amount of energy emitted by a star per unit time. It's a fundamental property that helps astronomers understand stellar characteristics and evolution.

2. How Does the Calculator Work?

The calculator uses the Stefan-Boltzmann law:

Where:

• \( L \) — Luminosity (Watts)
• \( R \) — Radius of the star (meters)
• \( \sigma \) — Stefan-Boltzmann constant (5.670374419×10⁻⁸ W/m²·K⁴)
• \( T \) — Effective temperature (Kelvin)

Explanation: The equation shows that luminosity depends strongly on temperature (to the fourth power) and on the star's surface area (4πR²).

3. Importance of Luminosity Calculation

Details: Luminosity is crucial for determining a star's size, distance, and life stage. It helps classify stars on the Hertzsprung-Russell diagram and understand stellar evolution.

4. Using the Calculator

Tips: Enter the star's radius in meters and its effective temperature in Kelvin. Both values must be positive numbers.

5. Frequently Asked Questions (FAQ)

Q1: How does luminosity relate to apparent brightness?
A: Apparent brightness is luminosity divided by 4πd², where d is the distance to the star. The same star appears dimmer when farther away.

Q2: What are typical luminosity values for stars?
A: Our Sun has L ≈ 3.828×10²⁶ W. Stars range from 10⁻⁴ L☉ (red dwarfs) to 10⁶ L☉ (supergiants).

Q3: Why use Kelvin for temperature?
A: Kelvin is an absolute temperature scale required for the Stefan-Boltzmann law (0 K = absolute zero).

Q4: Can this calculate solar luminosity?
A: Yes, using R☉ ≈ 6.957×10⁸ m and T☉ ≈ 5778 K gives the Sun's luminosity.

Q5: What if I only know the star's mass?
A: For main sequence stars, luminosity roughly follows L ∝ M³.⁵, but this calculator requires radius and temperature.