Astronomy Final Exam: Chapters 13, 14, & 15

Question 1

What are the two processes where fusion can take place?

Answer 1

Proton-proton chains & carbon-nitrogen-oxygen (CNO) cycle

Question 2

A more massive star has what type of lifetime?

Answer 2

Shorter lifetime because nuclear fuel burns quicker

Question 3

What is the Chandrasekhar Limit?

Answer 3

The maximum mass of a stable white dwarf

Question 4

How many white dwarfs are out there?

Answer 4

8

Question 5

What is the energy source of a white dwarf?

Answer 5

Thermal energy

Question 6

What is a white dwarf?

Answer 6

• dense low massive object with no nuclear fuel in core
  -Bigger than Earth but half as massive as the Sun

Question 7

What is a planetary nebulae?

Answer 7

The region of cosmic gas & dust formed from the cast-off outer layers of a dying star

Question 8

What is a supernova?

Answer 8

A colossal explosion of a star

Question 9

What do supernova form?

Answer 9

Forms other stars due to shock wave of death collecting gas & dust

Question 10

How often does a supernova happen?

Answer 10

3x a century

Question 11

What are the types of supernovas?

Answer 11

Type II & Type Ia

Question 12

How do Type II Supernova form?

Answer 12

Rapid collapse & violent explosion of a massive star

Question 13

How do Type Ia Supernova form?

Answer 13

Binary system collision with one of the stars being a white dwarf

Question 14

What is a nova?

Answer 14

An explosion from the surface of a white-dwarf star in a binary star system

Question 15

When does a nova occur?

Answer 15

When a white dwarf “steals” gas from a companion star

Question 16

What are event horizons?

Answer 16

The opening of a black hole where an observer would see time stopping & light is unable to escape

Question 17

What is the Schwarzschild Radius?

Answer 17

The radius below which the gravitational attraction between the particles of a body must cause it to undergo irreversible gravitational collapse

Question 18

How massive are black holes?

Answer 18

3-10 solar masses

Question 19

What is a black hole?

Answer 19

A region of spacetime where gravity is so strong that nothing, including light or electromagnetic waves, have enough energy to escape its event horizon

Question 20

What are neutron stars?

Answer 20

When a massive star runs out of fuel & collapses

Question 21

What are pulsars?

Answer 21

Highly magnetized rotating neutron stars that emit beams of electromagnetic radiation out of its magnetic poles

Question 22

What is the mass of neutron stars?

Answer 22

1.35 x the Sun’s mass usually

Question 23

What is neutron degeneracy pressure?

Answer 23

A pressure exerted by dense material consisting of fermions (like electrons in white dwarfs)

Question 24

What happens to neutron star pairs when they meet?

Answer 24

Merger leads to the formation of a more massive neutron star or a black hole

Question 25

Can the Sun ever become a black hole?

Answer 25

No, it would need to be 20x more massive

Question 26

What is an isolated black hole?

Answer 26

A black hole that traps light due to intense gravitational field & cannot be seen directly

Question 27

What are accretion disks?

Answer 27

A disk-like flow of gas, plasma, dust, or particles around any object in which what's orbiting in the gravitational field of the object loses energy & angular momentum as it slowly spirals inward

Question 28

What are globular clusters?

Answer 28

Conglomeration of stars

Question 29

Where are globular clusters located?

Answer 29

Galaxy's halo

Question 30

Why are globular clusters important?

Answer 30

Estimate the age of the Universe

Question 31

What does the Galaxy's disk include?

Answer 31

Spiral arms

Question 32

What happens in the spiral arms?

Answer 32

Sites of ongoing star formation

Question 33

OB stars are good tracers because of why?

Answer 33

Their short lifetimes tell astronomers where recent stars were formed

Question 34

What is the Galaxy's disk mostly made of?

Answer 34

gas & dust

Question 35

Where is the Supermassive Black Hole?

Answer 35

The Galactic Center of the Milky Way

Question 36

How was the Supermassive Black Hole discovered?

Answer 36

Radio telescopes discovered a dim speck

Question 37

How many solar masses is the Supermassive Black Hole?

Answer 37

4.154 +- 0.014 million solar masses

Question 38

What were the first stars?

Answer 38

Population II

Question 39

What were the first stars composed of?

Answer 39

Hydrogen & helium

Question 40

What is a cepheid variable star?

Answer 40

A variable star that pulses radically, varying in diameter & temperature

Question 41

What do cepheid variable stars measure?

Answer 41

Interstellar & intergalactic distances

Question 42

What is dark matter?

Answer 42

Nonluminous material that is postulated to exist in space (theorized to make approx. 85% of matter)

Question 43

What is the Milky Way Galaxy?

Answer 43

Galaxy that is includes our solar system

Question 44

How massive is the Milky Way Galaxy?

Answer 44

1.5 trillion solar masses