Page "Luminosity" Paragraph 3

Hertzsprung – Russell diagram identifying stellar luminosity as a function of temperature for many stars in our solar neighborhood. In astronomy, luminosity is the amount of electromagnetic energy a body radiates per unit of time.

It is measured in two forms: apparent ( visible light only ) and bolometric ( total radiant energy ).

A bolometer is the instrument used to measure radiant energy over a wide band by absorption and measurement of heating.

When not qualified, the term " luminosity " means bolometric luminosity, which is measured either in the SI units, watts, or in terms of solar luminosities.

A star also radiates neutrinos, which carry off some energy, about 2 % in case of our Sun, producing a stellar wind and contributing to the star's total luminosity.