Question

1) Which of the following statements are true regarding the event horizon of a black hole? (Select all that apply.)

1. The event horizon is the location that marks the "point of no return" for a black hole. Anything that crosses the event horizon can never escape.

2. The Schwarzschild radius specifies the location of the event horizon.

3. The event horizon is the location where the escape velocity is equal to the speed of light.

4. Inside the event horizon, the escape velocity is less than the speed of light.

5. The event horizon specifies the maximum mass that a star can have before collapsing into a black hole.

2) Which of the following statements are true regarding how black holes are formed? (Select all that apply.)

1. All stars eventually produce black holes at the end of their lives, because white dwarfs are unstable and will collapse into black holes.

2. Stars with masses that are eight times as large as our sun's or more will produce a black hole when they collapse and explode in a supernova.

3. Two white dwarfs or neutron stars can produce a black hole if they collide.

4. If a white dwarf accretes material from a companion star in a binary system, it will eventually collapse into a black hole.

3) Which of the following answers is the best response to the statement: "everything near a black hole will be sucked in."

1. True, the gravity of a black hole is so strong that it is impossible to escape no matter where you are.

2. False, the presence of accretion disks shows us that nothing that falls near a black hole is absorbed.

3. True, black holes are large, and it is unlikely that an object will not fall into a black hole once the black hole's gravity begins to pull on it.

4. False, black holes are relatively tiny compared to other objects with similar mass, so material that falls near a black hole will orbit it rather than fall directly in.

4) Calculate the Schwarzschild radius that Jupiter would have if it were to turn into a black hole.

Hint: Jupiter's mass is 1.9 x 10²⁷ kg.

Hint: the gravitational constant is 6.67 x 10^-11.

5) As a black hole gains mass via accretion, its radius will...

1. Remain the same

2. Increase

3. Decrease

Answer 1

1. True statsments regarding the event horizon of a black hole are :

(a)The event horizon is the location that marks the "point of no return" for a black hole. Anything that crosses the event horizon can never escape.

(b) The Schwarzschild radius specifies the location of the event horizon.

2. True statments regarding how black holes are formed are:

(c) Two white dwarfs or neutron stars can produce a black hole if they collide.

(d) If a white dwarf accretes material from a companion star in a binary system, it will eventually collapse into a black hole.

3. The best response to the statement: "everything near a black hole will be sucked in." is :

(c) True, black holes are large, and it is unlikely that an object will not fall into a black hole once the black hole's gravity begins to pull on it.

4. Schwarzschild radius that Jupiter would have if it were to turn into a black hole is given as

rs = 2GM / c2

where G = gravitational constant

M = mass of Jupiter

c = speed of light

5.  As a black hole gains mass via accretion, its radius will... (b) increase.