Description
Transcript: The Stephan-Boltzmann Law says that the luminosity of a star is proportional to its surface area and the fourth power of the temperature. If the luminosity is in watts, the radius is in meters, the temperature is in Kelvins, then the constant of proportionality, the Stefan-Boltzmann constant, is 5.67 times 10-8. This means that a star with twice the area has twice the luminosity, twice the number of photons emitted per second, but a star with twice the temperature has 24 or sixteen times the luminosity, sixteen times as much light emitted per second. So hotter stars emit more light per second and more light per unit area.
Transcript: Since light has a finite speed, three hundred thousand kilometers per second, there’s an inevitable consequence called light travel time. In terrestrial environments light essentially travels instantly or appears to travel fast. The finite speed of light, three hundred thousand...
Published 07/24/11
Transcript: Some stars in the sky, somewhat hotter than the Sun with temperatures of 5 thousand to 10 thousand Kelvin, have very low luminosities in the range of one-hundredth to one-thousandth the Sun’s luminosity. Application of the Stephan-Boltzmann Law shows that they must be physically...
Published 07/24/11
Transcript: Certain rare stars in the sky with either red or blue colors are extremely luminous, up to a million times the luminosity of the Sun. Application of the Stephan-Boltzmann Law shows that their sizes must be in the range of ten to a thousand times the size of the Sun. These...
Published 07/24/11