Standard candles

Need to know

What you need to know

• 25.1 Standard candles.
• Luminosity L is defined as the total power output of radiation emitted by a star .
• It is measured in Watts.
• The observed amount of intensity F is the observed amount of intensity, or the radiant power transmitted normally through a surface per unit of area, of radiation measured on defined as Earth.
• Light leaving a star can be assumed to be a uniformly spread out like a spherical shell.
• Hence, the inverse square law of flux can therefore be calculated using 𝐹 = 𝐿 4𝜋𝑑 2 Here L is the luminosity of the source (watts), d is the distance between the star and Earth (m).

Explanation

Standard candles

1. 25.1 Standard candles.
2. Luminosity L is defined as the total power output of radiation emitted by a star .
3. It is measured in Watts.
4. The observed amount of intensity F is the observed amount of intensity, or the radiant power transmitted normally through a surface per unit of area, of radiation measured on defined as Earth.