Luminosity is an absolute measure of radiated electromagnetic power (light), the radiant power emitted by a light-emitting object over time. ... In SI units, luminosity is measured in joules per second, or watts. In astronomy, values for luminosity are often given in the terms of the luminosity of the Sun, L_⊙.

How is luminosity calculated?

A star's luminosity, which is how much energy is emitted per second from the star, is measured in Watts or in solar luminosities (L⊙) where 1L⊙ = 3.85 x 1026 Watt. We determine a star's luminosity by measuring its distance and its apparent brightness, which we call its apparent magnitude.

What is luminosity and How Is It measured?

The luminosity of an object is a measure of its intrinsic brightness and is defined as the amount of energy the object emits in a fixed time. It is essentially the power output of the object and, as such, it can be measured in units such as Watts.