astro ch 14

Question 1

What color does this wavelength correspond to in the visible-light spectrum?

Answer 1

Green

Question 2

Why do you think the Sun appears white or yellow to our eyes?

Answer 2

Because the Sun radiates in other colors, and because the atmosphere scatters blue light stronger than red light.

Question 3

What two physical processes balance each other to create the condition known as gravitational equilibrium in stars?
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Answer 3

gravitational force and outward pressure

Question 4

According to modern science, approximately how old is the Sun?

Answer 4

4.5 billion years

Question 5

If the Sun suddenly stopped emitting neutrinos, what might we infer (after checking that our neutrino detectors were still operational)?

Answer 5

Fusion reactions in the Sun have ceased within the past few minutes

Question 6

The light radiated from the Sun’s surface reaches Earth in about 8 minutes, but the energy of that light was released by fusion in the solar core about

Answer 6

a few hundred thousand years ago

Question 7

What causes the cycle of solar activity?

Answer 7

changes in the organization of the Sun’s magnetic field

Question 8

What is the solar wind?

Answer 8

a stream of charged particles flowing outward from the surface of the Sun

Question 9

In the late 1800s, Kelvin and Helmholtz suggested that the Sun stayed hot because of gravitational contraction. What was the major drawback to this idea?

Answer 9

It predicted that the Sun could shine for about 25 million years, but geologists had already found that Earth is much older than this

Question 10

Every second, the Sun converts about 600 million tons of hydrogen into 596 million tons of helium. The remaining 4 million tons of mass is

Answer 10

converted to an amount of energy equal to 4 million tons times the speed of light squared

Question 11

The Sun’s surface seethes and churns with a bubbling pattern. Why?

Answer 11

We are seeing hot gas rising and cool gas falling as a result of the convection that occurs beneath the surface

Question 12

What color does this wavelength correspond to in the visible-light spectrum?

Answer 12

Infrared, and thermal radiation with such a peak will be red.

Question 13

How does this color compare with that of the Sun?

Answer 13

Sunspots seem to be dark spots because the surface of the Sun is much brighter.

Question 14

Which of the following changes would cause the fusion rate in the Sun’s core to increase?

Answer 14

an increase in the core temperature
a decrease in the core radius

Question 15

Which of the following must occur for a star’s core to reach equilibrium after an initial change in fusion rate?

Answer 15

If the fusion rate initially increases, then the core expands.
If the fusion rate initially decreases, then the core contracts

Question 16

What would happen if the fusion rate in the core of the Sun were increased but the core could not expand?

Answer 16

The Sun’s core would start to heat up, and the rate of fusion would increase even more.

Question 17

In which layer(s) of the Sun does nuclear fusion occur?

Answer 17

core

Question 18

Which of the following layers of the Sun can be seen with some type of telescope? Consider all forms of light, but do not consider neutrinos or other particles.

Answer 18

chromosphere
photosphere
corona

Question 19

Which of the following best explains why nuclear fusion requires bringing nuclei extremely close together?

Answer 19

Nuclei normally repel because they are all positively charged and can be made to stick only when brought close enough for the strong force to take hold.

Question 20

The proton-proton chain is

Answer 20

the specific set of nuclear reactions through which the Sun fuses hydrogen into helium

Question 21

What do we mean when we say that the Sun is in energy balance?

Answer 21

The amount of energy released by fusion in the Sun’s core equals the amount of energy radiated from the Sun’s surface into space

Question 22

A salesman attempts to convince you to purchase a “solar neutrino shield” to protect you and your family. (It’s even “on sale!”) Why do you turn down this excellent offer?

Answer 22

Neutrinos rarely, if ever, interact with other matter.

Question 23

Which of the following is the best answer to the question, “Why does the Sun shine?”

Answer 23

As the Sun was forming, gravitational contraction increased the Sun’s temperature until the core become hot enough for nuclear fusion, which ever since has generated the heat that makes the Sun shine.

Question 24

When we say that the Sun is a ball of plasma, we mean that __________.

Answer 24

the Sun consists of gas in which many or most of the atoms are ionized (missing electrons)

Question 25

What is the Sun's approximate composition (by mass)?

Answer 25

70% hydrogen, 28% helium, 2% other elements

Question 26

What do sunspots, solar prominences, and solar flares all have in common?

Answer 26

They are all strongly influenced by magnetic fields on the Sun

Question 27

Satellites in low-Earth orbits are more likely to crash to Earth when the sunspot cycle is near solar maximum because

Answer 27

Earth's upper atmosphere tends to expand during solar maximum, exerting drag on satellites in low orbits

Question 28

Which of the following choices is not a way by which we can study the inside of the Sun?

Answer 28

We can send a space probe into the Sun's photosphere.

Question 29

The dark spots in this photo (such as the one indicated by the arrow) represent what we call

Answer 29

sunspots

Question 30

How does the Sun's mass compare to Earth's mass?

Answer 30

The Sun's mass is about 300,000 times the mass of the Earth.

Question 31

How is the sunspot cycle directly relevant to us here on Earth?

Answer 31

Coronal mass ejections and other activity associated with the sunspot cycle can disrupt radio communications and knock out sensitive electronic equipment.

Question 32

Why do sunspots appear dark in pictures of the Sun?

Answer 32

They actually are fairly bright, but appear dark against the even brighter background of the surrounding photosphere.

Question 33

The Sun's visible surface (that is, the surface we can see with our eyes) is called the

Answer 33

photosphere

Question 34

What is the overall fusion reaction that converts mass into other forms of energy in the Sun’s core?

Answer 34

4 hydrogen nuclei become 1 helium nucleus

Question 35

When we refer to the solar thermostat, we are referring to the idea that

Answer 35

the Sun’s core temperature naturally stays stable

Question 36

The energy balance that contributes to the solar thermostat is a balance between

Answer 36

the energy released in the core by fusion and the energy radiated from the Sun’s surface into space