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ASTRONOMY SCIENCE OLYMPIAD MASTER
EXAM QUESTIONS AND ANSWERS 2025
Optical double - ...ANSWER... ✔ ✔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 - ...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
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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
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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
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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
ASTRONOMY SCIENCE OLYMPIAD MASTER
EXAM QUESTIONS AND ANSWERS 2025
Optical double - ...ANSWER... ✔ ✔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 - ...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
,2|Page
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
,3|Page
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
, 4|Page
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
