chapter 24 study questions (astronomy)

19. Which of the following can a black hole not "eat" (swallow)?

another black hole

25. Far away from a black hole (at the distance of another star), which of the following is a possible way to detect it?

search for flickering x-rays being given off from an accretion disk around the black hole, as it "eats" part of a neighbor star.

1. The equivalence principle (principle of equivalence) says that....

the effects of gravity are equivalent to the effects of acceleration.

17. The astronomer who first worked out the mathematical description of black hole event horizons was....

Karl Schwarzschild

6. Einstein suggested that the regular change (advance) in the perihelion of the planet Mercury could be explained by:

a distortion in spacetime caused by the gravity of the Sun.

12. According to the general theory of relativity, light and other radiation coming from a white dwarf or a neutron star should (and experiments show that it does) exhibit.

a gravitational redshift

15. Deep inside a black hole (and hidden from our view) is the compressed center, where all the "stuff" of the star goes. Astronomer call this central point....

a singularity.

10. When a light wave leaves a region of strong gravity, compared to the same wave leaving a spaceship in empty space, the wave in strong gravity will have.

all of the above.

24. What type of main sequence star is most likely to become a black hole?

an O-type star.

20. Suppose each of the following objects could collapse into a black hole. Each black hole would have a sphere around it that is the limit for escape -- once you are inside this region, you cannot get away. For which object would this region be the largest in diameter?

an entire galaxy of stars (with about a billion stars in it).

28. Astronomers have concluded that growing supermassive black holes (which have millions of times the Sun's mass or more) is pretty unlikely at our location in the Milky Way Galaxy. Where do they think is the most likely place in the Milky Way for such a supermassive black hole?

at the center of the Milky Way Galaxy, where matter is more crowded.

2. If you are in a freely falling elevator near the top of a tall building, as the elevator falls, your weight would be:

equal to zero - you would be weightless

27. When one member of a binary star system is a black hole, and astronomers detect flickering x-rays coming from the system, where are these x-rays usually coming from?

from a disk of material around the black hole (material that has been pulled from the companion star and is falling toward the black hole).

29. What is a key reason that gravitational waves are so much harder to detect than electro-magnetic (e-m) waves?

gravitational waves are much weaker than e-m waves, and therefore require very, very precise equipment to detect.

23. A handsome, rich, but vain movie star notices that he is starting to age, and consults you as his astronomy expert, to see if you can find an astronomical way to slow down his aging. Putting aside practical considerations (such as the fact that we cannot travel to other stars), which of the following strategies would IN THEORY allow him to age more slowly than the rest of humanity.

he should be in orbit around the Earth, and expose himself to as many cosmic rays as possible.

13. To predict whether a star will ultimately become a black hole, what is the key property of the star we should look at?

mass

21. Wearing a very accurate watch, you volunteer to go on a mission to a black hole in a spaceship that has powerful rockets. You are able to orbit the black hole and stay a little distance outside of the event horizon. Compared to watches on Earth, your watch near the black hole will run:

more slowly

33. Some years after college (and after you recover from your astronomy class,) you get married and exchange gold rings with your sweetheart. What connection is there between the gold in those rings and recent observations of gravitational waves?

our new understanding is that significant amounts of gold in the universe are produced in the mergers of neutron stars, which can be detected with gravitational waves

22. When scientists say that "black holes have no hair", what do they mean?

that once a black hole forms, very little information can be extracted from it about the material that is now inside.

When astronauts aboard the International Space Station (ISS) in space let go of an orange, it just floats there. Why is that?

the ISS is falling around the Earth, and in free fall, things feel no weight.

30. The first, indirect detection of gravitational waves in the 1970s involved...

the black hole in the Cygnus X-1 system.

9. In 1959, Pound and Rebka did an experiment to test the prediction of Einstein's theory of general relativity about the relationship between the pace of time and the strength of gravity. When two identical atomic clocks, one on the ground floor and one on the top floor, were compared,

the clock on the top floor ran a tiny bit slower.

14. The region around a black hole where everything is trapped, and nothing can get out to interact with the rest of the universe, is called....

the event horizon.

18. Once a black hole forms, the size of its event horizon is determined only by....

the mass inside the event horizon

In the first direct detection of gravitational waves by LIGO in 2015, the waves came from....

the merger of two black holes.

16. In the far future, a starship becomes trapped inside the event horizon of a black hole. Although the crew discovers that their ship cannot out, they at least want to send a message to other ships in the area to stay away from the danger zone. If they send out a message in the form of a radio wave, what will be its fate?

the message will never emerge from the event horizon.

8. According to Einstein's general theory of relativity, the stronger a star's gravity,

the slower time run near it.

32. The first time that astronomers observed both gravitational waves and electro-magnetic waves from the same event, what they were observing was:

the spiraling toward each other of two neutron stars.

11. From which of the following will a wave of light show the greatest gravitational redshift:

the sun

5. Which of the following statements about the way the mass of a white dwarf affects spacetime is correct?

the white dwarf mass will attract light, and pull it in a curved path; spacetime is not affected.

26. Which of the following objects do many astronomers believe is a black hole?

Cygnus X-1

7. When Einstein proposed his General Theory of Relativity, he suggested some pretty strange ideas about space, time, and gravity. How did scientists in 1919 show that Einstein's theory described the behavior of the real world and wasn't just a crazy hypothesis?

by observing starlight coming close to the Sun during an eclipse.

4. According to the general theory of relativity, the presence of mass...

causes a curvature (or warping) of spacetime.