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Luminosity and power?

by Mafia
Tags: luminosity, power
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Apr27-12, 12:47 PM
P: 1
If one star is say 10 times more luminous than another star would that mean it would have 10 times more power as in W? And would that relationship continue with increased luminousity as in a star 1000 times more luminous would have 1000 times more power?
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Apr27-12, 12:52 PM
P: 2,195
Basically, yes. Luminosity has units of energy per time, and is typically measured in ergs/sec(CGS) or joules/sec(MKS), with joules per second being the same as watts.
Apr28-12, 10:08 AM
PF Gold
P: 519
As a layman, the way I read the H-R diagram, white dwarfs have less luminosity and less absolute visual magnitude than most main sequence stars, yet can have higher surface temperature, higher frequency color index (B-V), and higher surface current density. But perhaps this has nothing to do with power?

Respectfully submitted,

Apr28-12, 10:26 AM
P: 2,195
Luminosity and power?

It does have to do with power. The luminosity is the power of the radiation that the stars emit. Since a star is roughly a blackbody, the total luminosity of a star is [tex]L =4\pi r^2 * \sigma T^4 [/tex]
where sigma is the Stefan-Boltzmann constant. White dwarfs emit a lot of radiation per square cm of surface area because their temperature is high, but their total luminosity is low because their radius is so small.

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