ASTRON 1F03 Lecture Notes - Lecture 12: Angular Distance, Parsec, Proper Motion

• School: McMaster University
• Department: Astronomy
• Course: ASTRON 1F03
• Professor: Hugh Couchman

Document Summary

Measuring the stars. distance(parsecs)= 1/parallax (arcseconds), 1 parsec is the distance to the earth of a star that has an observed parallax of 1 arc second. Proper motion: angular distance travelled in one year. Transverse motion: motion perpendicular to our line of sight. Radial motion: motion parallel lo our line of sight. Luminosity (absolute brightness) : total power radiated by an object. Apparent brightness: depends on luminosity and distance=> apparent brightness= l/(4pi r^2) The lower the magnitude the brighter the star m-m= 5log(d/10pc), m= apparent magnitude, m= absolute magnitude (magnitude the star would have if viewed from a distance of 10 pc). There are 7 types of stella spectra, correspondent to different temperatures: O b a f g k m, 10 subdivisions 0 (hottest)-10(coolest) Luminosity is a strong function of mass=> l= cm^4. => the more massive and thus luminous the star, the shorter its lifespan.