Remember that luminosity is the total amount of energy produced in a star and radiated into space in the form of E-M radiation. The Sun radiates 3.9 x 10 33 ergs/sec.   An "erg" is not a joke, it is a unit of energy

Start with the Sun

Can you answer these questions...

Q. What is the Solar Luminosity at the distance of Mars (1.5 AU)?

Still the same, 1 solar luminosity. The Martian "solar constant" will be smaller by a factor of 1.5 x 1.5, but added up over the entire surface of the sphere centered on the Sun with radius 1.5AU, the luminosity is the same. Luminosity is an intrinsic property of the Sun.

Q. What is the Solar Luminosity at the surface of the Sun?   Right, it's still 1 solar luminosity.


How does the Sun manage to produce all that energy and maintain that production for at least 4.5 billions years?

What about the Luminosity of those other stars?

Once we have the distance to any other star, we can combine that with the apparent brightness and the inverse-square law for light dimming to determine the "intrinsic brightness" or luminosity of the star.

We can therefore determine a luminosity for all the stars for which we have trigonometric parallax measurements.
You will find out that there is a pretty big range from 25 L down to 0.00001 L