Exam 3

Question 1

Describe how the process of gravitational contraction can make a star hot?

Answer 1

When a star contracts in size, gravitational potential energy is converted to thermal energy

Question 2

What two physical processes balance each other to create the condition known as gravitational equilibrium in stars?

Answer 2

gravitational force and outward pressure

Question 3

The source of energy that keeps the Sun shining today is what?

Answer 3

nuclear fusion

Question 4

What are the appropriate units for the Sun’s luminosity?

Answer 4

watts

Question 5

From center to outward, which of the following lists the layers of the Sun in the correct order?

Answer 5

core, radiation zone, convection zone, photosphere, chromosphere, corona
CRCPCC CROCPOC!!!!!

Question 6

Which of these groups of particles has the greatest mass? a helium nucleus with two protons and two neutrons, four electrons, four individual protons

Answer 6

four individual protons

Question 7

At the center of the Sun, fusion converts hydrogen into what?

Answer 7

helium, energy, and neutrinos

Question 8

What two pieces of information would you need in order to measure the masses of stars in an eclipsing binary system?

Answer 8

the time between eclipses and the average distance between the stars

Question 9

List the stars from brightest to dimmest based on the info:(A: 100L 8 ly, B: 400L 20 ly, C: 400L 40ly, D: 100L 10ly, E: 200L 20 ly)

Answer 9

A, D+B, E, C

Question 10

What are characteristics of red giants and supergiants?

Answer 10

very cool but very luminous, found in upper right of the HR diagram

Question 11

What are characteristics of main sequence stars?

Answer 11

The sun, very hot and very luminous, majority of stars in galaxy

Question 12

What are characteristics of white dwarfs?

Answer 12

very hot but very dim, not much larger in radius than Earth

Question 13

Compared to a main sequence star with a short lifetime, a main sequence star with a long lifetime is what?

Answer 13

less luminous, cooler, smaller, and less massive

Question 14

Compared to a high luminosity main sequence star, stars in the upper right of the HR diagram are what?

Answer 14

cooler and larger in radius

Question 15

Compared to a low luminosity main sequence star, stars in the lower left of the HR diagams are what?

Answer 15

hotter and smaller in radius

Question 16

Which of these star clusters is oldest? A cluster whose brightest main sequence stars are white, yellow, or all colors

Answer 16

a cluster whose brightest main sequence stars are yellow

Question 17

Rank the stars colors based on surface temperature from highest to lowest

Answer 17

blue, green, orange, red

Question 18

Does the HR diagram luminosity go from lowest to highest or highest to lowest?

Answer 18

lowest to highest

Question 19

Does surface temperature relate to spectral type?

Answer 19

surface temperature increases from left to right from spectral type O(bgor)M

Question 20

Approximately what core temperature is required before hydrogen fusion can begin in a star?

Answer 20

10 million K

Question 21

The main source of energy for a star as it grows in size to become a red giant is what?

Answer 21

hydrogen fusion in a shell surrounding the central core

Question 22

What stars do not have fusion occurring in their core?

Answer 22

red giants

Question 23

What would stars be like if hydrogen had the smallest mass per nuclear particle?

Answer 23

nuclear fusion would not occur in stars of any mass

Question 24

What happens to the core of a high mass star after it runs out of hydrogen?

Answer 24

it shrinks and heats up

Question 25

What happens when a main sequence star exhausts its core hydrogen fuel supply?

Answer 25

the core shrinks while the rest of the star expands

Question 26

Suppose that a white dwarf is gaining mass through accretion in a binary system. What happens if the mass someday reaches the 1.4 solar mass limit?

Answer 26

The white dwarf will explode completely as a white dwarf supernova

Question 27

A typical neutron star is more massive than our Sun and about the size (radius) of?

Answer 27

a small asteroid

Question 28

What happens to time on the falling rocket while observed from orbit of the black hole?

Answer 28

Time runs increasingly slower as the rocket approaches the black hole

Question 29

When observed from orbit of the black hole, the observer see the falling rocket…

Answer 29

slow down as it approaches the event horizon and never actually crosses the event horizon

Question 30

Why will the falling rocket disappear when we know that we’ll never see the rocket cross the event horizon?

Answer 30

its light will become so redshifted that it will be undetectable

Question 31

If you were inside the falling rocket, you notice your own clock to be running…

Answer 31

at a constant, normal rate as you approach the event horizon

Question 32

If you were in the falling rocket, from your own viewpoint you would….

Answer 32

accelerate as you fall and cross the event horizon completely unhindered

Question 33

Is degeneracy pressure can only arise from interactions among electrons?

Answer 33

NO