PCS 181 Lecture Notes - Lecture 5: Large Magellanic Cloud, Proper Motion, Main Sequence

• School: Ryerson University
• Department: Physics
• Course: PCS 181
• Professor: Margaret Buckby

Document Summary

Distance units: lightyear = ly: distance that light travels in one year, 1 ly = 9. 5 1015 m, parsec = pc: 1 pc = 3. 26 ly, astronomical unit = au: average distance between earth and sun. Apparent magnitude (m) problem: w pegasi is an 8th magnitude (m = 8) star, fomalhaut is 1st magnitude (m=1) M=6 is barely visible, m=8 is even fainter. So fomalhaut (m=1) is brighter than w pegasi. We know by absolute magnitude: absolute magnitude = apparent magnitude (m) of star at a distance of 10 parsecs (=32. 6 light year) from us, to convert m to m. M = m + 5 5log(d) on the formula sheet. 1 parsec is more than 3 times bigger than 1 light year. Most apparent magnitude is -26. 5 (= brightest celestial object) (more negative apparent magnitude => brighter. ) M = -26. 5 + 5 5log(4. 7 x 10-6) Given: dacen = 4. 4 ly, apparent magnitude is m = -0. 01.