ASTA02H3 Lecture Notes - Photon, Black-Body Radiation, Sirius
Document Summary
Describes how stars look to human eyes. The brightness of stars is measured using the magnitude scale. Ancient astronomers divided the stars into six magnitudes. A star may have negative or positive magnitude. A. a -1 mv star is brighter than a +3. 5. Distance is measured through ground-based parallax measurements. Its spectrum was amongst the first to be measured. Q. the mv of a number of stars is given- sort them in order of descending brightness. Total electromagnetic output of energy per unit of time. Most convenient way to do measurement of time in astronomy. Apparent magnitude is a function of flux. Defined as the energy (measured in joules) per second per one square meter. By definition obeys the inverse square law. Not a reliable measure for the true brightness of a star. True measurement for the intrinsic brightness of the stars is called absolute magnitude.
