B Apparent magnitude / absolute magnitude / luminosity

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1. Oct 28, 2017

mtig

Hello,

When we talk about the luminosity, apparent magnitude or absolute magnitude of a star, are we talking about all wavelengths of EM radiation or just a certain range?

I've read that luminosity is basically the power output of all types of radiation, but the apparent magnitude scale is subjective implying that it only accounts for visible light.

2. Oct 28, 2017

phyzguy

Wikipedia's definition says, "In astronomy, magnitude is a logarithmic measure of the brightness of an object, measured in a specific wavelength or passband, usually in the visible or near-infrared spectrum." This is correct, in that we are usually talking about the radiation in a specific band. When no band is specified, it is usually assumed that the band is visible light. If the radiation at all wavelengths is included, then we usually call the quantity bolometric luminosity or bolometric magnitude. If it is a specific band, then there will often be a subscript, such as $m_B$, which would be the magnitude in the B band of wavelengths.

3. Oct 29, 2017

mtig

Ok thank you.