3.1

Calculate the escape velocity from a neutron star. Here's what to do: 1. Look up the mass of the Sun in kilograms (one 'solar mass'). 2. Assume the mass of the neutron star is two solar masses, M = 2 x (answer from 1). 3. Assume the radius of the Neutron Star is 10,000 meters (= R). 4. With these units, use G = 6.67 x 10-11 . 5. Calculate the escape velocity in m/s by plugging the above numbers into the formula vesc = square root of 2 G M divided by R end root 77,000,000 m/s 154,000,000 m/s 231,000,000 m/s 462,000,000 m/s

231,000,000 m/s

Calculate the Schwarzschild radius for the Sun. Here's what to do: 1. Use M = 1 solar mass = ______ kg, use the number you looked up in the previous problem. 2. To get an answer in meters, use G = 6.67 x 10-11 and c = 300,000,000 . 3. Plug the numbers into the formula RS = 2 G M / c2 . 2964 m 29,644 m 296,444 m 296,444,444 m

2964 m

Which of the following is a remnant of a dying star? White dwarfs Neutron star Black hole All of the above

All of the above

Gravitational waves Are how pulsars pulse. Carry material into black holes. Are traveling distortions of space and time. Do not carry energy.

Are traveling distortions of space and time

Two important properties of young pulsars are Rapid rotation and no magnetic field. No rotation and strong magnetic field. Extremely rapid rotation and a weak magnetic field. Extremely rapid rotation and a strong magnetic field.

Extremely rapid rotation and a strong magnetic field.

A method for identifying a black hole is to Observe them directly through the space-based telescopes. Look for voids (holes) in the star fields. Look for its effect on nearby companions. Search for radio waves from the accretion disk.

Look for its effect on nearby companions

Can astronomers see black holes? No, but they can sometimes see disks of gas being drawn into the black hole. No, but with their enormous size they frequently block our view of more distant objects. Yes, but most of the emitted light is infrared radiation. Yes, many of the "stars" seen at night are actually black holes.

No, but they can sometimes see disks of gas being drawn into the black hole.

Which of the following can actually escape a black hole? Very high energy gamma-rays. Visible light. Very low energy radio waves. None of the above.

None of the above.

These are neutron stars! Accretion Disks Novae Pulsars White Dwarfs

Pulsars

What is the escape velocity at the event horizon of a black hole? Speed of sound. Supersonic speed. Half the speed of light. Speed of light.

Speed of light.

From which of the following will a wave of light show the greatest gravitational redshift: a white dwarf a giant planet like Jupiter Earth the sun

a white dwarf

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 a longer wavelength a lower frequency less energy a gravitational redshift all of the above.

all of the above

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 finding x-rays from a black hole by using an H-R diagram for a nearby cluster of stars by discovering the process of nuclear fusion by dropping different weights from very tall buildings by observing starlight coming close to the Sun during an eclipse

by observing starlight coming close to the Sun during an eclipse

According to Einstein's general theory of relativity, the stronger a star's gravity, the weaker its pull on another star will be the slower time runs near it the weaker the x-rays we see from it the smaller the event horizon will be of the black hole it makes the less space-time around it will be distorted

the slower time runs near it