Test #2

Question 1

What process is responsible for creating the sun’s energy?

1. Nuclear fission
2. Thermo-nuclear radiation
3. Charged particles smashing into each other (particle collisions)
4. Nuclear fusion

Answer 1

4. Nuclear fusion

Question 2

Why does the sun’s size remain stable, and not rapidly expand or shrink?

Answer 2

The sun is in gravitational equilibrium, meaning the outward pressure caused by the sun’s hot gas balances the inward force of gravity. Thus, the sun’s size remains stable.

Question 3

Nuclear fusion turns hydrogen into:

1. Heavy hydrogen (Deuterium).
2. Plasma, helium-4 and radioactive particles.
3. Helium, energy and neutrinos.

Answer 3

3. Helium, energy and neutrinos.

Question 4

Matter found in the sun is in the phase of matter known as the ___.

1. Ions
2. Gases
3. Sublimated condensates
4. Plasmas
5. Solids
6. Non-newtonian solids
7. Bose–Einstein condensates

Answer 4

4. Plasmas

Question 5

Which is closest to the temperature of the sun’s core?

1. 10,000,000 Kelvins
2. 237,000,000 Kelvins
3. 2.76 Kelvins
4. 70,000,000,000 (seventy billion) °C

Answer 5

1. 10,000,000 Kelvins

Question 6

If a neutrino can escape from the solar core within minutes, how long does it take for a photon?

Answer 6

About ½ million years

Question 7

The number of sunspots and solar activity in general peaks every ___.

Answer 7

11 years

Question 8

The sunspot cycle shows a consistent __-year pattern of activity dating back more than ___ years.

Answer 8

The sunspot cycle shows a consistent 11-year pattern of activity dating back more than 300 years.

Question 9

Stellar parallax is used to measure the ________.

1. Sizes of stars
2. Distances of stars
3. Temperatures of stars
4. Radial velocity of stars
5. Brightness of stars

Answer 9

2. Distances of stars

Question 10

A star’s proper motion is its _________ across the sky.

Answer 10

A star’s proper motion is its apparent annual motion across the sky.

Question 11

What types of Electro-Magnetic Radiation from space reach the surface of Earth?

1. Radio & microwaves
2. X-rays & ultraviolet light
3. Infrared & gamma rays
4. Visible light & radio waves
5. Visible & ultraviolet light

Answer 11

4. Visible light & radio waves

Question 12

Earth’s ______ filters most ______ light, but allows ____ waves & ____ light to reach the ground.

Answer 12

Earth’s atmosphere filters most ultraviolet light, but allows radio waves & visible light to reach the ground.

Question 13

Which of the following has a fundamentally different nature than the other four?

1. proton
2. electron
3. neutron
4. atomic nucleus
5. photon

Answer 13

5. photon

Question 14

Which of these is NOT a form of electromagnetic radiation?

1) gamma rays
2) infrared
3) sound
4) visible light
5) radio

Hint: Only four of these are apart of the electromagnetic spectrum.

Answer 14

3) sound

Sound is vibrations made by waves moving through a medium (air, water..)

Question 15

The distance between successive wave crests defines the ________ of a wave.

1) wavelength
2) frequency
3) period
4) amplitude
5) energy

Answer 15

The distance between successive wave crests defines the wavelength of a wave.

Question 16

The frequency at which a star’s intensity is greatest depends directly on its ____.

1) radius.
2) mass.
3) magnetic field.
4) temperature.
5) direction of motion.

Answer 16

4) temperature

Question 17

Wien’s law means that

1) Hotter stars are longer in wavelength.

2) Colder stars emit less radiation, but out of the radiation they DO emit, it’s mostly visible light.

3) Lower frequency means less waves, less waves means light.

4) Hotter stars produce much more high frequency light.

Answer 17

4) Hotter stars produce much more high frequency light.

Question 18

True or false?

All electromagnetic radiation is light, but we can only see a small portion of this radiation—the portion we call visible light.

Answer 18

True

Question 19

If a light source is approaching you, its wavelengths will be ____-shifted. This causes the ________ to be shorter in ________.

Answer 19

If a light souce is approaching you, its wavelengths will be blue-shifted. This causes the spectral lines to be shorter in wavelength.

Question 20

The wavelengths of emission lines produced by an element

1) depend on its temperature.
2) are identical to its absorption lines.
3) depend on its density.
4) are different than its absorption lines.
5) depend on its intensity

Answer 20

2) are identical to its absorption lines.

Elements absorb or emit the same wavelengths of light based on their electron energy levels.

Question 21

Analyzing a star’s spectral lines can tell us about all of these EXCEPT

1) its composition.
2) its surface temperature.
3) its transverse (side-to-side) motion.
4) its rotation.
5) its density.

Answer 21

3) its transverse (side-to-side) motion.

Only motion towards or away from us influences a star’s spectral lines.

Spectra can also tell us about a star’s magnetic field.

Question 22

The visible light we see from our Sun comes from which part?

1) core
2) corona
3) photosphere
4) chromosphere
5) convection zone

Hint: When looking at a photograph, you are looking at a drawing of light. A photon is a packet of light, derived from the greek word phôs (light).

Answer 22

3) photosphere

The photosphere is a relatively narrow layer below the chromosphere and corona, with an average temperature of about 6000 K.

Question 23

The Sun is as stable as a star because

Answer 23

gravity balances forces from pressure.

Question 24

The proton–proton cycle involves which kind of fusion process?

1) carbon (C) into oxygen (O)
2) helium (He) into carbon (C)
3) hydrogen (H) into helium (He)
4) neon (Ne) into silicon (Si)
5) oxygen (O) into iron (Fe)

Answer 24

3) hydrogen (H) into helium (He)

In the proton-proton cycle, four Hydrogen nuclei (protons) fuse into one Helium nucleus, releasing gamma rays and neutrinos.

Question 25

Which of the following quantities do you need in order to calculate a star’s luminosity? 1) apparent brightness (flux) 2) Doppler shift of spectral lines 3) color of the star 4) distance to the star 5) 1 and 4

Answer 25

5) 1 and 4

Question 26

What are the two most important intrinsic properties for classifying stars?

Answer 26

Luminosity and surface temperature

Question 27

Wien’s law tells us that the hotter an object, the ________ the peak wavelength of its emitted light. 1) longer 2) more green 3) heavier 4) shorter 5) more constant

Answer 27

4) shorter ## Footnote Wien’s law states that hotter stars appear more **blue** in color, and cooler stars appear more **red** in color. Blue light has a wavelength that is shorter and more compressed than red light.

Question 28

We estimate the surface temperature of a star by using 1) its color. 2) the pattern of absorption lines in its spectrum. 3) Wien’s law. 4) differences in brightness as measured through Red and Blue filters. 5) All of the above.

Answer 28

5) All of the above.

Question 29

Which spectral classification type corresponds to a star like the Sun? 1) O 2) A 3) F 4) G 5) M

Answer 29

4) G ## Footnote The OBAFGKM classification scheme is based on absorption lines.

Question 30

The key difference between the spectra of B stars and G stars is 1) B stars show strong Hydrogen lines; G stars weaker Hydrogen lines. 2) B stars show few metal lines; G stars show many. 3) B stars have no metal atoms. 4) G stars have no Hydrogen atoms. 5) Both 1 and 2 are true.

Answer 30

1) B stars show strong Hydrogen lines; G stars weaker Hydrogen lines. ## Footnote The original OBAFGKM sequence was arranged alphabetically by the strength of Hydrogen absorption lines. B stars had strong hydrogen lines, G stars had weak lines.

Question 31

Astronomers can estimate the size of a star using 1) apparent brightness. 2) direct observation of diameter. 3) temperature. 4) distance to the star. 5) 1, 2, and 3 are all true.

Answer 31

5) 1, 2, and 3 are all true.

Question 32

Eclipsing binary stars are very useful for determining the 1) ages of stars. 2) absolute luminosities of stars. 3) masses of stars. 4) distances to stars. 5) rotation rates of stars.

Answer 32

3) masses of stars.

Question 33

What is the single most important characteristic in determining the course of a star’s evolution? 1) density 2) absolute brightness 3) distance 4) surface temperature 5) mass

Answer 33

5) mass ## Footnote A star’s mass determines how fast it forms, its luminosity on the main sequence, how long it will shine, and its ultimate fate.

Question 34

How did the Sun become hot enough for fusion in the first place?

Answer 34

As the Sun was forming, it grew hotter as it shrank in size because gravitational contraction converted gravitational potential energy into thermal energy. Gravitational contraction continued to shrink the Sun and to raise its central temperature until the core became hot and dense enough for nuclear fusion.

Question 35

What are the major layers of the Sun, from inside out?

Answer 35

Core, radiation zone, convection zone, photosphere, chromosphere, and corona.

Question 36

Why does fusion occur in the Sun’s core?

Answer 36

The core temperature and pressure are so high that colliding nuclei can come close enough together for the strong force to overcome electromagnetic repulsion and bind them together.

Question 37

How do we know what is happening inside Sun?

Answer 37

We can construct theoretical models of the solar interior using known laws of physics, and check the models against observations of the Sun’s output and studies of “sun quakes” and of solar neutrinos.

Question 38

Describe the sunspot cycle.

Answer 38

The sunspot cycle, or the variation of the number of sunspots on the Sun’s surface, has an 11 year period. The magnetic field flip-flops every 11 years, for a 22 year magnetic cycle. Sunspots first appear at mid-latitudes at solar minimum, then become increasingly more common near the Sun’s equator as the next minimum approaches.

Question 39

What is the surface of the Sun like?

Answer 39

The photosphere is composed of hot, churning gases. There is no solid or liquid region in the Sun.

Question 40

How are stars classified into spectral types?

Answer 40

Stars are classified according to their spectra, with different spectral types generally corresponding to different temperatures. In order from hottest to coolest, the major spectral types are O, B, A, F, G, K, and M. These are subdivided into numbered categories; for example, the hottest A stars are type A0 and the coolest A stars are type A9, which is slightly hotter than F0.

Question 41

Does a star’s spectral type depend on its composition?

Answer 41

No. All stars are made primarily of hydrogen and helium, and the main factor in determining a star’s spectral type is its surface temperature.

Question 42

What is the average temperature of the SURFACE of the sun?

Answer 42

6,000 K