ASTRONOMY CERTIFICATION
EVALUATION EXAMS SET FULL QUESTIONS
AND COMPLETE SOLUTION
●● Visual binary
Answer: 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
Answer: If one significantly brighter, not possible to see both directly
Exitence deduced by observing oscillatory motion of visible member
●● Spectrum binary
Answer: two superimposed independent discernible spectra
Doppler effect causes shifting of spectral lines
●● Spectroscopic binary
Answer: 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
Answer: Visual binaries combined with parallax info
Visual binaries with radial velocities available over complete orbit
Eclipsing double-line spectroscopic binaries
●● O stars
Answer: Hottest blue-white stars with few lines
Strong He II absorption (sometimes emission) lines
He I absorption lines becoming stronger
●● B stars
Answer: Hot blue-white
He I absorption lines strongest at B2
H I (Balmer) absorption lines getting stronger
●● A stars
Answer: White
Balmer absorption lines strongest at A), becoming weaker later
Ca II absorption lines becoming stronger
,●● F stars
Answer: Yellow-white
Ca II lines continue to increase, Balmer lines decrease
Neutral metal absorption lines (Fe I, Cr I)
●● G stars
Answer: Yellow
Solar-type spectra
Ca II increase
Fe I, other neutral metal increase
●● K stars
Answer: Cool orange
Ca II H & K strongest K0, then decrease
dominated by metal absorption
●● M stars
Answer: Cool red
Molecular absorption bands (TiO, VO)
Neutral metal absorption lines remain strong
, ●● L stars
Answer: 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
Answer: Coolest, Infrared
Strong methane, CO decrease
●● Wolf-Rayet stars
Answer: 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
EVALUATION EXAMS SET FULL QUESTIONS
AND COMPLETE SOLUTION
●● Visual binary
Answer: 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
Answer: If one significantly brighter, not possible to see both directly
Exitence deduced by observing oscillatory motion of visible member
●● Spectrum binary
Answer: two superimposed independent discernible spectra
Doppler effect causes shifting of spectral lines
●● Spectroscopic binary
Answer: 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
Answer: Visual binaries combined with parallax info
Visual binaries with radial velocities available over complete orbit
Eclipsing double-line spectroscopic binaries
●● O stars
Answer: Hottest blue-white stars with few lines
Strong He II absorption (sometimes emission) lines
He I absorption lines becoming stronger
●● B stars
Answer: Hot blue-white
He I absorption lines strongest at B2
H I (Balmer) absorption lines getting stronger
●● A stars
Answer: White
Balmer absorption lines strongest at A), becoming weaker later
Ca II absorption lines becoming stronger
,●● F stars
Answer: Yellow-white
Ca II lines continue to increase, Balmer lines decrease
Neutral metal absorption lines (Fe I, Cr I)
●● G stars
Answer: Yellow
Solar-type spectra
Ca II increase
Fe I, other neutral metal increase
●● K stars
Answer: Cool orange
Ca II H & K strongest K0, then decrease
dominated by metal absorption
●● M stars
Answer: Cool red
Molecular absorption bands (TiO, VO)
Neutral metal absorption lines remain strong
, ●● L stars
Answer: 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
Answer: Coolest, Infrared
Strong methane, CO decrease
●● Wolf-Rayet stars
Answer: 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
