Problem Set 4:
Ch 16: 2
What is Kelvin-Helmholtz contraction? Why is it ruled out as a source
of the present-day Sun’s energy?
Ch 16: 14
What is a neutrino? Why is it useful to study neutrinos coming from
the Sun? What do they tell us that cannot be learned from other avenues of research?
Ch 16: 32
(a) Estimate how many kilograms of hydrogen the Sun has consumed
over the past 4.56 billion years, and estimate the amount of mass that the Sun has lost
as a result. Assume that the Sun’s luminosity has remained constant during that time.
(b) In fact, the Sun’s luminosity when it first formed was only about 70% of its
present value. With this in mind, explain whether your answers to part (a ) were an
overestimate or an underestimate.
Ch 17: 1
luminosity.
Explain the difference between a star’s apparent brightness and its
Ch 17: 16
If a red star and a blue star both have the same radius and both are the
same distance from Earth, which one has the larger radius? Explain why.
Ch 17: 19
Sketch a Hertzsprung-Russell diagram. Indicate the regions on your
diagram occupied by (a) main-sequence stars, (b) red giants, (c) supergiants, (d) white
dwarfs, and (e) the Sun.
Ch 19: 5
On what grounds are astronomers able to say that the Sun has about 7
9
x 10 years remaining in its main-sequence stage?
Ch 19: 21
What is the difference between Population I and Population II stars?
In what swense can the stars of one population be regarded as the “children” of the
other population?
Ch 19: 24
Why do Cepheid stars pulsate? Why are these stars important to
astronomers who study galaxies beyond the Milky Way?
Ch 20: 14
On an H-R diagram, sketch the evolutionary track that the Sun will
follow from when it leaves the main sequence to when it becomes a white dwarf.
Approximately how much mass will the Sun have when it becomes a white dwarf?
Where will the rest of the mass go?
Ch 20: 39
The Ring Nebula is a planetary nebula in the constellation Lyra. It has
an angular size of 1.4 arcmin x 1.0 arcmin and is expanding at the rate of about 20
km/s. Approximately how long ago did the central star shed its outer layers? Assume
that the nebula is 2,700 ly from Earth.
Ch 20: 41
(a) Calculate the wavelength of maximum emission of the white dwarf
Sirius B. In what part of the electromagnetic spectrum does this wavelength lie? (b)
In a visible-light photograph such as Figure 20-8, Sirius B appears much fainter than
its primary star. By in an image made with an X-ray telescope, Sirius B is the
brighter star. Explain the difference.