1.
Describe the stars in this picture.
2.
Briefly explain how we can learn about the lives of stars,
even though their lives are far longer than human lives.
3.
In what ways are all stars similar? In what ways do they
differ?
4.
How is a star's apparent brightness related to its
luminosity? Explain by describing the inverse square law for light.
5.
Briefly explain how we use stellar parallax to determine a
star's distance. Once we know a star's distance, how can we determine its luminosity?
6.
Other than parallax, is there a way to measure the distance
to stars? Explain carefully
7.
What do we mean by a star's apparent and absolute magnitudes?
How are they related to apparent brightness and luminosity?
8.
What does this illustrate?
9.
What do we mean by a star's spectral type? How is a star's
spectral type related to its surface temperature and color? Which stars are
hottest and coolest in the spectral sequence OBAFGKM?
10.
If stars are mostly hydrogen and helium why don't we see
hydrogen and helium spectral lines in all stars?
11.
I saw a star with a temperature of 10,000K with no hydrogen
lines. What is happening?
12.
What are the three basic types of binary star systems? Why
are binaries so important to measuring masses of stars?
13.
Draw a sketch of a basic Hertzsprung-Russell (H-R) diagram.
Label the main sequence, giants, supergiants, and white dwarfs. Where on this
diagram do we find stars that are cool and dim? Cool and luminous? Hot and dim?
Hot and luminous?
14.
What do we mean by a star's luminosity class? What does the
luminosity class tell us about the star? Briefly explain how we classify stars
by spectral type and luminosity class.
15.
What is the defining characteristic of a main-sequence star?
Briefly explain why massive main-sequence stars are more luminous and have
hotter surfaces than less massive main-sequence stars.
16.
Which stars have longer lifetimes: massive stars or less
massive stars? Explain why.
17.
Why is a star's birth mass its most fundamental property?
18.
How do giants and supergiants differ from main-sequence
stars? What are white dwarfs?
19.
How does the luminosity of a pulsating variable star change
with time?
20.
What is this? About how old is it?
21.
Describe in general terms how open clusters and globular
clusters differ in their numbers of stars, ages, and locations in the galaxy.
22. Explain why H-R diagrams look
different for star clusters of different ages. How does the location of the main-sequence turnoff point tell us the
age of the star cluster?
23.
The table below gives basic data for several bright stars; M
is absolute magnitude, m is apparent magnitude, Sp T is spectral type and Lum
Class is luminosity class. Use these data to answer the following questions.
Include a brief explanation with each answer.
|
Star |
M |
m |
Sp T |
Lum Class |
|
Aldebaran |
-0.2 |
+0.9 |
K5 |
III |
|
Alpha Centauri A |
+4.4 |
0.0 |
G2 |
V |
|
Antares |
-4.5 |
+0.9 |
M1 |
I |
|
Canopus |
-3.1 |
-0.7 |
FO |
II |
|
Fomalhaut |
+2.0 |
+1.2 |
A3 |
V |
|
Regulus |
-0.6 |
+1.4 |
B7 |
V |
|
Sirius |
+1.4 |
-1.4 |
Al |
V |
|
Spica |
-3.6 |
+0.9 |
B1 |
V |
a. Which star appears brightest in our sky? b. Which star
appears faintest in our sky? c. Which star has'
the greatest luminosity? d. Which star has the least
luminosity? e. Which star has the highest surface temperature? f. Which star
has the lowest surface temperature? g. Which star is most similar to the Sun?
h. Which star is a red supergiant? i. Which star has the largest radius? j.
Which stars have finished burning hydrogen in their cores? k.
Among the main-sequence stars listed, which one is the most massive? l. Among the main-sequence stars listed,
which one has the longest lifetime?
24.
Using the information in this H-R diagram,
describe how Proxima Centauri differs from Sirius. Do the same for Sirius B and the Sun.
25.
Suppose you could travel to Jupiter and observe changes in
positions of nearby stars during one orbit of Jupiter around the Sun. Describe
how those changes would be different from what we measure from Earth. How would
your ability to measure the distances to stars be different from the vantage
point of Jupiter?
26.
Describe what would happen to the surface temperature of a
star if its radius doubled in size with no change in luminosity.
27.
This
figure shows an eclipsing binary system consisting of a small blue star and
a larger red star. Explain why the decrease in apparent brightness of the
combined system is greater when the blue star is eclipsed than when the red
star is eclipsed.
28.
Suppose you are observing two binary star systems at the same
distance from Earth. Both are spectroscopic binaries consisting of similar
types of stars, but only one of these binary systems is a visual binary. Which
of these star systems would you expect to have the greater Doppler shifts in
its spectra? Explain your reasoning.
29.
Does the H-R diagram have limits? Why or why not?
Does It Make
Sense?
Decide whether the statement makes sense (or is
clearly true) or does not make sense (or is clearly false). Explain clearly;
not all these have definitive answers, so your explanation is more important
than your chosen answer.
30.
Two stars that look very different must be made of different
kinds of elements.
31.
Two stars that have the same apparent brightness in the sky
must also have the same luminosity.
32.
Sirius looks brighter than Alpha Centauri, but we know that
Alpha Centauri is closet because its apparent position in the sky shifts by a
larger amount as Earth orbits the Sun.
33.
Stars that look red have hotter surfaces than stars that look
blue.
34.
Some of the stars on the main sequence of the H-R diagram are
not converting hydrogen into helium.
35.
The smallest, hottest stars are plotted in the lower
left-hand portion of the H-R diagram.
36.
Stars that begin their lives with the most mass live longer
than less massive stars because they have so much more hydrogen fuel.
37.
Star clusters with lots of bright, blue stars of spectral
type O and B are generally younger than clusters that don't have any such
stars.
38.
All giants, supergiants, and white dwarfs were once
main-sequence stars.
39.
Most of the stars in the sky are more massive than the Sun.
