1.
1a.
2.
2a.
3.
3a.
6.
6a.
7.
7a.
8.
8a.
9.
9a.
10.
10a.
11.
11a.
12.
12a.
12.
12a.
13.
13a.
14.
14a.
15.
15a.
16.
16a.
17.
17a.
18.
18a.
19.
19a.
20.
20a.
21.
Star A has a distance of 3 parsecs. What is its parallax angle?
1/3 arcsecs.
Star A has a parallax angle of 5 arcseconds. What is its distance?
1/5 parsecs.
If you move closer to a light source, say going from 10m away to 5m away, what happens to the brightness
of the light source perceived by your eye?
The light source gets brighter by a factor of 4 since its closer to you by a factor of two.
The Earth is about 150 million kilometers from the Sun. The apparent brightness of the Sun in our sky
is 1300W/m2. Using just these two facts alone work out the luminosity of the Sun.
Use B = L/4πd2 , where B is the brightness, L is the luminosity and d is the distance. Then B =
1300W/m2 and d, the distance from Earth to Sun is 150 × 109 m. So L = B × 4 × πd2 = 1300 × 4 ×
3.141 × 150 × 109 W atts.
What would be the apparent brightness of the Sun if we were located at half Earth’s distance from the
Sun.
It woul dbe 4 times as bright, ie. 4 × 1300W/m2.
What would be the apparent brightness of the Sun if we were located at twice Earth’s distance from
the Sun.
It would be four times less ie. 1300/4W/m2.
What would be the apparent brightness of the Sun if we were located at five times Earth’s distance
from the Sun.
It would be 1300/25W/m2.
Stars A and B have absolute magnitudes of -2 and 0 respectively. Which is brighter and by how much?
Which appears brighter and by how much?
A is brighter by a factor of 2.512 × 2.512. Cant say anything about how bright they appear.
Stars A and B have apparent magnitudes of -2 and 0 respectively. WHich is brighter and by how much?
Which appears brighter and by how much?
Cant say anything about which is brighter but star A appears brighter by a factor (2.512 × 2.512).
Which has a greater luminosity, a star with absolute magnitude -4 or a star with absolute magnitude
+6? By how much?
The -4 magntude star has a greater luminosity by a factor 2.51210 .
Star I is of spectral type O2 and star II is of spectral type O3. Which star is hotter?
Star I.
Which of the following stars is the most massive: a) G2V b) K8V c) O1V?
c) because its the hottest and hence brightest and hence most luminous.
What do all the stars in question 13) have in common?
They all lie on the main sequence and hence are burning hydrogen to helium on the main sequence.
Star X has its radius increased by a factor of 3 and its temperature increased by a factor of two. What
happens to its luminosity?
Its luminosity increases by a factor of 9 × 16.
Why does a M type luminosity class I star have to be really big?
Its really cool yet its a supergiant (class I). The only way it can do this is if its really big.
Which of the following layers of the Sun is the coolest? a) photosphere b) chromosphere c) corona?
a)
Is it true that in the convective transport of energy, material actually moves from point A to B delivering
energy?
Yes.
If the Sun’s central temperature increased a bit, would more or less energy be created there?
Temperature increases - more energy generated in core, more pressure created which halts the contraction.
If the Sun’s central temperature were to increase a little bit, why would it not be cause for worldwide
panic?
The solar thermostat would ensure that the SUn would remain stable.
True or False: there were no rocks beyond the frost line in the initial Solar Nebula.
1
21a.
22.
22a.
23.
23a.
24.
24a.
25.
25a.
26.
26a.
False, there were some rocks. There was much more hydrogen compounds in solid form though.
True or False: there was no hydrogen inside the frost line in the initial Solar Nebula.
False, there was hydrogen in gaseous form.
True or False: Terrestrial Planets have to be more dense than Jovian planets.
True.
True or False: Hydrogen compounds were gaseous outside the frost line in the initial Solar Nebula.
False. Outside the frost line hydrogen compounds were in solid form.
True or False: All the planets pretty much orbit the Sun in the same plane.
True.
Sirius A has a luminosity of 26L . And a surface temperature of 9400K. What is its radius?
Use the formula L = 4πσR2 T 4 , using L = 26 × 1026 W, and T = 9400K.
2