QUIZ 5 YOUR NAME:___

Possibly useful formula: or

Where L=angular momentum, M=mass, R= radius, spin rate

1. For a star, core-collapse models for SNII predict that a ``neutron'' star will be left behind at the center of the SNII remnant. Which of the following properties are predicted for the neutron star?

   ___ Rapid rotation

   ___ Large abundances of S- and R-process elements

   ___ Mass less than

   ___ Strong magnetic field

2. If the Sun expanded to 4 times its current radius

   (a) would it spin faster, slower or the same as it does now (1/30 revolution per day)?

   (b) By what factor?

3. What is the best explanation for a pulsar?

   ___ Rapidly spinning Black Hole with a large magnetic field

   ___ Rapidly spinning neutron star that has collapsed to within it's event horizon

   ___ Rapidly spinning neutron star with a strong magnetic field aligned with along its spin axis

   ___ None of these is correct

4. Suppose we observe a SNII remnant and do not find a pulsar. Which of the following are possible explanations for this non-detection?

   ___ The beamed radiation of the pulsar is oriented such that it does not reach the earth

   ___ Instead of forming a neutron star, the core collapse resulted in a black hole

   ___ The star that exploded was not massive enough to form a neutron core

   ___ None of the above are correct

5. If the Earth could be compressed to a small enough radius, it would become a black hole, True or False?

6. Which of the following are predictions of Special Relativity?

   ___ The clock in a spaceship traveling at a high velocity with respect to the Earth will run more slowly than a clock on Earth

   ___ If you perform an experiment to measure the speed of light, you will always get the same answer independent of your velocity

   ___ Neutron stars will be observable as pulsars

   ___ Clocks near black holes will run backwards

7. To the best of our current knowledge, if a neutron star exceeds then the gravitational forces overcome neutron degeneracy forces and the neutron star begins to collapse. What stops the collapse?

8. The equation for escape velocity is where G is a constant, M is the mass of the object from which escape is to be attempted and R is the radius from which the escape will be made. Given this equation

   (a) Compare the escape velocities from the surface of the Earth for a hydrogen atom (with a mass of grams) and the Space Shuttle (with a mass of grams). Think about this carefully - it is right on the edge of being a trick question.

   (b) Use a little algebra to manipulate the equation to solve for radius in terms of the other variables.

9. What is an event horizon?

   ___ The outer surface of the collapsed core of a massive star

   ___ the extent of the gravitational pull from a black hole

   ___ the boundary near a singularity inside of which the escape velocity exceeds the speed of light

   ___ all of the above are correct