PHYS 183 Lecture Notes - Lecture 14: Spectroscopic Notation, Spectroscopy, Measure R

• School: McGill University
• Department: Physics
• Course: PHYS 183
• Professor: Gilbert Holder

Document Summary

Sun is just one example of a star. Star: factory of nuclear fusion, creates heavy elements, produces heat and light. Time scales much longer than human: understand by studying many stars today. Closest star is 260000 times distance to sun. Recall: distance to sun = 1 au = 1. 5x1011m. Closest star (after sun) is proxima centauri: 1 light year = 1 ly = 9. 5x1015m. It is 4. 3 ly away: this is 1. 36 pc or 260000 au. Stars far away: explains why much fainter than sun. Define luminosity: amount of energy star radiates per second: equivalent to power, e. g. 100 w light bulb: 100 joules per second. For a spherical central source, light emitted equally in all direction: radiating isotropically (isotropic radiation) Total energy is conserved, so gets spread out to a larger area: a = 4(pi)d2. Because of the squared nature of the above equation, going twice as far will result in a 4 times decrease.