From what I understand, in the equation [itex]P=\sigma AT^4[/itex], P is the power output of the star which is the energy radiated per second in EM radiation of all frequencies, and I think luminosity is also defined as the energy radiated per second in EM radiation of all frequencies. Therefore luminosity is equal to power output, so the equation tells us the luminsoty.(adsbygoogle = window.adsbygoogle || []).push({});

But then I get confused trying to relate this to intensity, brightness and magnitudes. I have read than absolute magnitude is a measure of luminosity on a logarithmic scale, and apparent magnitude is a measure of intensity on a logarithmic scale, however it seems to me that both intensity and luminsoty refer to energy from all frequencies of radiation, but absolute and apparent magnitudes refer only to the energy from visible light. I am also trying to figure out how brightness fits in. Is brightness more of a qualitative term and apparent magnitude is a quantitative measure of brightness, and absolute magnitude a quantitative measure of inherent brightness? This would make more sense to me as it seems that brightness and magnitudes refer to visible light only, while lumnosity and intensity refer to EM radiation of all freqencies...

Thank you in advance for any help clearing this up :)

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# Stefan-Boltzmann law, luminosity, brightness and magnitude?

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