Download Chapter #10 Question #27: (c) Four individual protons. During

Chapter #10
Question #27:
(c) Four individual protons. During nuclear fusion, four protons are converted into a helium
nucleus. The mass of the helium nucleus is lesser than the combined mass of the individual
protons. The difference in mass is converted into energy in accord with Einstein’s equation
E = mc2
Question #31:
(a) They are cooler than their surroundings. Sunspots occur where the magnetic field lines loop
out of the solar interior. These magnetic field lines suppress convection within the sunspot from
occurring. As a result, the hot plasma is unable to enter the region. The sunspot plasma is cooler
than the surrounding regions and hence appear darker.
Chapter #11
Question #26:
(b) get smaller. According to the equation d = 1/p, if the distance to a star increases, its parallax
angle must decrease and vice versa.
Question #27:
(c) apparent brightness and distance. The luminosity of a star is related both to its apparent
brightness as well as its distance given by the inverse square law: L = 4d2b; where d is the
distance to the star and b is its apparent brightness.
Question #30:
(a) a main sequence A star. Mass is the most important property of stars on the main sequence.
Stars further up on the main sequence have more mass than stars down on the main sequence.
Thus, a main sequence A star will have more mass than a main sequence G star which will have
more mass than a main sequence M star.
Chapter #12
Question #17:
This statement makes sense. Massive stars fuse higher elements in their core during their death.
The final result is an iron core which is released to the interstellar space during a high mass star
supernova. A massive star supernova that blew up before the formation of the solar system
would have released iron into the surrounding space which was used up by our solar system
during its formation.
Question #28:
(a) An object not quite massive enough to be a star. If the mass of the protostar is less than 0.08
solar masses, gravity is unable to contract the core to a point where it is able to get hot enough
for hydrogen fusion to occur. These failed stars are known as brown dwarfs.
Question #34:
(b) a white dwarf. Our sun is a low mass star. Death of low mass stars results in a white dwarf.
Thus, when our sun dies, it will turn into a white dwarf the size of our Earth.
Chapter #13
Problem #19:
This statement makes sense. The Schwarschild radius of the black hole with a 1Msun mass is
3km. The effects of the black hole would be seen only at a distance of 10 times the Schwarschild
radius i.e. 30km. The closest planet from the sun, Mercury is at a distance much greater than
30km from the sun. Thus, the orbits of the planets orbiting the sun would not change if the sun
suddenly became a 1Msun black hole.
Problem #33:
(c) a 106Msun black hole. The larger the radius of the event horizon, the weaker is the tidal force.
Thus, the 106Msun has the largest event horizon and thus the weakest tidal force.
Extra Credit
Chapter #12, Problem #44
According to the inverse square law:
bBeteleuse = Betelgeuse
4dBetelgeuse2
bSirius =
LSirius
4dSirius2
Apparent Brightness of Betelgeuse = LBetelgeuse/ 4dBetelgeuse2
Apparent Brightness of Sirius
LSirius / 4dSirius2
= LBetelgeuse * dSirius2
LSirius
dBetelgeuse2
= 1010 * 8.62
26
4272
= 156*103
Thus, Betelgeuse would appear 156*103 times brighter than Sirius when it explodes as a
supernova.