Distances -- stellar parallax

Distances Parsec -- distance at which a star has a parallax of one second of arc (pc) kiloparsec (kpc) , megaparsec (mpc) Light year – distance light travels in 1 year (lyr) 1 pc ~ 3.3 lyr

Motions --- along the line of sight Doppler Effect Change in l or n divided by rest l 0 or n 0 Equals velocity (v) of approach or recession divided by c l - l 0 = v l 0 c Longer l, redshift , away, vel is + Shorter l, blueshift , toward, vel is - Radial Velocity

Motions -- across the line of sight Proper Motion -- angular motion Plus distance – transverse velocity

“APPARENT VISUAL MAGNITUDES” Sun: m = -27 Moon: -10 Venus: -4 Mars: -2.5 Sirius: -1.4 Vega: 0.0 Antares: 1.0 Polaris: 2.3

“APPARENT VISUAL MAGNITUDES” BRIGHTEST STAR (SIRIUS): m = -1.4 20th BRIGHTEST STAR: +1.5 FAINTEST VISIBLE: ... about 6.5 WITH BINOCULARS: about 8 6-INCH TELESCOPE: about 12 PLUTO: 14 LIMIT WITH MODERN DETECTORS ON BIG TELESCOPES: 20 -- 28

Atomic Spectra – spectra of the elements

Kirchoff’s Laws

The Spectra of the Stars and Spectral Classification Early classification – the Harvard system OBAFGKM -- a temperature sequence – decreasing

Binary Stars – Weighing and Measuring the Stars > 50% of all stars are multiple

Three Types Visual Eclipsing – light curve Spectroscopic – velocity curve

The HR Diagram Fundamental diagram of stellar astrophysics

HR Diagram for solar neighborhood

Relative Sizes

The Largest Stars – Red Supergiants