Astronomy Science Olympiad Master Latest Update Graded A+

Astronomy Science Olympiad Master Latest Update Graded A+ Optical double not actually binaries simply two stars lying along same line of sight (similar RA & dec) Not gravitationally bound Not usefull in determining stellar masses Visual binary both stars resolved independently if orbital pd not too long, can monitor motion provides angular separation from center of mass If dist known, linear separations can be calculated Astrometric binary If one significantly brighter, not possible to see both directly Exitence deduced by observing oscillatory motion of visible member Spectrum binary two superimposed independent discernible spectra Doppler effect causes shifting of spectral lines Spectroscopic binary if period not too long Orbital motion has component along line of sight Periodic shift in spectral lines observable Only 1 set of periodically varying spectral lines seen Systems able to provide us with mass determination Visual binaries combined with parallax info Visual binaries with radial velocities available over complete orbit Eclipsing double-line spectroscopic binaries O stars Hottest blue-white stars with few lines Strong He II absorption (sometimes emission) lines He I absorption lines becoming stronger B stars Hot blue-white He I absorption lines strongest at B2 H I (Balmer) absorption lines getting stronger A stars White Balmer absorption lines strongest at A), becoming weaker later Ca II absorption lines becoming stronger F stars Yellow-white Ca II lines continue to increase, Balmer lines decrease Neutral metal absorption lines (Fe I, Cr I) G stars Yellow Solar-type spectra Ca II increase Fe I, other neutral metal increase K stars Cool orange Ca II H & K strongest K0, then decrease dominated by metal absorption M stars Cool red Molecular absorption bands (TiO, VO) Neutral metal absorption lines remain strong L stars Very cool, dark red Stronger in infrared Strong molecular absorption bands of metal hydrides, water, CO, Na, K, Rb, Cs, Alkalis TiO, VO decrease T stars Coolest, Infrared Strong methane, CO decrease Wolf-Rayet stars discovered by C.J.E. Wolf and G. Rayet Paris Observatory in 1867 more than 220 WR identified, most likely more 25,000 to 100,000 K losing mass at over 10^-5 Solar masses per year Wind speeds of 800 to 3000+ kilometers per second Rapidly rotating Can have starting masses of under 20 solar masses No dramatic variability P Cygni profile Absorption trough at short-wavelength edge superimposed on rather broad emission peak FU Orionis contain instabilities in circumstellar accretion disk Results in 0.01 solar masses being dumped T-Tauri may go through several stages Herbig Ae/Be named for George Herbig spectral type A or B strong emission lines 2 to 10 solar masses