ASTRO/PHYS 1040: Elementary Astronomy, Dr. Sohl, Homework Chapters 9 & 10
Due at start of class, Tuesday November 1, 2011
score: ___/45 Name:
Name:
Name:
Part 1. Definitions and vocabulary.
Match the following words with the definitions below.
accretion disk
gravitational contraction
black hole
gravitational equilibrium
brown dwarf
gravitational redshift
Chandrasekhar limit
hydrogen shell burning
degeneracy pressure
main sequence turnoff point
electron degeneracy pressure
molecular clouds
escape velocity
neutron degeneracy pressure
event horizon
neutron star
evolutionary track
nova
general relativity
planetary nebula
protostar
pulsar
red giant
Schwarzschild radius
singularity
special relativity
stellar thermostat
supermassive black hole
supernova
white dwarf
1. Giant, cold, dark, clouds—made mostly of hydrogen molecules—where stars are born.
1.
2. For a star to be stable it must balance the forces of gravity and gas pressure, this is…
2.
3. Gravitational equilibrium and energy balance must be maintained, this acts like a…
3.
4. The internal pressure in stars and gas giants arising from atoms having no place else to go. 4.
5. When our Sun runs out of hydrogen in its core the surrounding layers collapse and start...
5.
6. When our Sun dies it will blow its outer layers off into space and becoming a large…
6.
7. The very hot dead corpse of our Sun. This will slowly cool down in time and fade away.
7.
8. The iron core of a massive star cannot produce energy. It collapses and explodes as a…
8.
9. We use this to determine the age of a cluster of stars.
9.
10. The laws of quantum mechanics don’t allow electrons to share the same space.
10.
11. A white dwarf’s mass must be <1.4MSun or else it will collapse. This is the…
11.
12. The explosion that comes from hydrogen gas accreting onto the surface of a white dwarf. 12.
13. In these stars gravitational pressure exceeds the limit of electron degeneracy pressure.
13.
14. Neutron stars are bizarrely massive; only this keeps it from collapsing more.
14.
15. A rapidly spinning neutron star. At first we thought this might be alien communications. 15.
16. When neutron degeneracy pressure can no longer support the star it collapses into a…
16.
17. A measure of the amount of energy needed to escape from the gravity of an object.
17.
18. Einstein’s theory, published in 1915, which explains gravity and the curvature of space.
18.
19. This is the point of no return for an object entering too close to a black hole.
19.
20. The size of a black hole, this is determined by the amount of mass.
20.
21. The center of a black hole, >3MSun, is an infinitely dense, infinitesimally small particle.
21.
22. Many spiral galaxies contain one of these massive objects at their centers.
22.
23. The plot of a star’s life on an H-R diagram.
23.
Part 2. Questions (2 points each, except problems 4 & 6, total = 22 points)
1. Which one property of a star will tell us almost everything we need to know about the star?
1.
2. Suppose the universe contained only low-mass stars. Would elements heavier than carbon exist? Why or why not?
3. Carefully and clearly sketch the evolutionary track of the rest
of the life of our Sun on the H-R diagram shown here. I’ve
marked the starting point for you.
4. (4 points) List the shells, in order from the center, for a high
mass star that has an inert core of iron. There are 8 shells.
Inner most shell
1. Silicon
5.
2.
6.
3.
7.
4.
8.
Outer most shell
5. If you came home to visit our solar system in 10 billion
years, what would you be most likely to find?
6. (4 points) The Schwarzschild radius can be calculated by knowing the mass of the black hole. The Schwarzschild radius is
the radius of the event horizon and it is 3km for every one solar mass unit of mass. What would be the diameter of a black
hole’s event horizon for a black hole of 4.5MSun? (You must clearly show your work to get credit and you must circle your
answer.)
7. This is impossible, but, what would happen to Earth’s orbit if the Sun were to suddenly become a black hole of exactly the
same mass?
8. Which of these objects would have the largest radius? (Circle it.)
1.2MSun white dwarf
1.5MSun neutron star
3.0MSun black hole
9. How do we measure the mass of the supermassive black hole at the center of our galaxy?
Jupiter