ASTR 1P01 Lecture 13: lecture 13

• School: Brock University
• Department: Astronomy
• Course: ASTR 1P01
• Professor: Bozidar Mitrovic

Document Summary

Higher the surface temperature the higher the wavelength. Bluish indicates cooler stars, meanwhile red indicates hotter. But, this is dependant on the radius of the body. We need luminosity and surface temperature to find the radius. Measuring the radius of a star (t) using the stefan-boltzmann law: The radius (r) of a star can be determined from its luminosity (l) and surface temperature: a universal constant (5. 7 x 10-8 w/m2k4) (= universal constant) If we determine luminosity and surface temperature, we can use the above relationship to determine the radius of the star. Note: if the temperature(t) is doubled, the luminosity increases by a factor of (24=16). If the radius is doubled the luminosity is increased by a factor of (22=4) Thus, the stars which are very luminous, but cool (red) must have very large: l(luminosity)= 120,000 l (symbol for solar) radii. (a large radius) vice versa, t(temperature)= 3,000 k = .