Mid-Term Exam
1. Which lives longer a B star or a G star? Justify your answer.
2. Balmer hydrogen lines are not seen in the spectra of either O stars or K stars. Why not?
3. What source of opacity
(a) Is independent of wavelength?
(b) Is strongly peaked a
Astronomy 310 Final Exam
1. The parallax of a star is 10 milli-arcseconds, and its apparent visual magnitude is 3.5. What is its
absolute visual magnitude?
(a) 5.5
(b) 3.5
(c) 1.5
(d) -1.5
(e) -3.5
2. A star has a radius of 3 Rd , and an eective temperatu
Astronomy 310 Final Exam
1. The parallax of a star is 10 milli-arcseconds, and its apparent visual magnitude is 3.5. What is its
absolute visual magnitude?
(a) 5.5
(b) 3.5
(c) 1.5
(d) -1.5 [*]
(e) -3.5
2. A star has a radius of 3 Rd , and an eective tempe
Assignment 6 Solutions [Revision : 1.2]
1. See Fig. 1 for the HRD.
(a) The ZAMS is at the beginning of all of the tracks.
(b) The KH contraction episode during H burning occurs on the massive-star tracks where
they turn to the blue, toward the end of the
Assignment 5 Solutions [Revision : 1.2]
1. See Figs. 1 and 2 for the plots of the
s as a function of log T .
(a) Zones where convection is taking place have
rad
ad .
(b) Convection is ecient when ad (i.e., the temperature gradient is close to adiabatic);
Assignment 4 Solutions [Revision : 1.2]
1. (a) Rearranging the rst-moment equation,
rad
c dPdr ,
F
Substituting in the expression for Prad, , this becomes
F
B
4
3 ddr .
The chain rule is used to write
dB
dr
ddB dT ,
T dr
from which we obtain the result
Assignment 2 Solutions [Revision : 1.2]
1. Because the enclosure is in thermal equilibrium, the radiation inside it will be blackbody
radiation.
(a) BB radiation is isotropic, and has a specic intensity given by the Planck function:
2
I
hc
B 25
(b) Integ
Assignment 1 Solutions [Revision : 1.2]
1. The Rayleigh-Jeans tail is the part of the blackbody spectrum where the photon energy h
hccfw_ is very small compared to the average energy per classical oscillator kT . The BB energy
density formula
8hccfw_5
u