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 tex2html_wrap_inline322 ergs/sec.

Start with the Sun

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.

What is the Solar Luminosity at the surface of the Sun?


A REALLY GOOD QUESTION: 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.

We can therefore determine the Luminosity for all the stars for which we have trigonometric parallax measurements. Find out that there is a pretty big range from tex2html_wrap_inline366 down to 0.00001 tex2html_wrap_inline368 .

Michael Bolte
Mon Jan 26 12:32:25 PST 1998