Tag Archives: luminosity

Solar Model

The Sun, a typical main-sequence star of spectral class G2, with a surface of composition X = 0.73 (mass fraction of hydrogen) and Z = 0.02 (mass fraction of metals). Current estimated age: 4.52e9 years. The standard solar model applies physical stellar … Continue reading

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Energy Sources and Luminosity

Where does the energy emitted by a star come from? One source is obviously gravitational potential energy U. If r decreases, U decreases too, and can be converted into radiated energy. However, because of the Virial Theorem (E = <U>/2) only 1/2 of … Continue reading

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Magnitude

Apparent magnitude (m): Apparent “brightness” of a star, as seen from Earth. Hipparcus first measured it, using a scale from 1 (brightest) to 6 (dimmest). Note that smaller values correspond to brighter starts! This scale was adopted and extended in … Continue reading

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