Deck 11: The Sun: Our Extraordinary Star

Question 1

Granulation, or the mottled appearance of the whole solar surface, is an indication of what physical process at work in the Sun?

A) outflow of neutrinos from the interior
B) rapid rotation of the Sun
C) thermonuclear fusion of hydrogen in the Sun's surface layers
D) convective motion of gases in the upper portion of the Sun's interior

Answer 1

convective motion of gases in the upper portion of the Sun's interior

Question 2

The temperature of the Sun's photosphere is nearly

A) close to 1 million K.
B) about 10,000 K.
C) 5800 K.
D) 4300 K.

Answer 2

5800 K.

Question 3

Spectral lines observed in the granules seen at the center of the Sun's disk are

A) split by the Zeeman effect due to the strong magnetic fields in the granule.
B) always redshifted because granules are caused by gas descending into the Sun from higher layers.
C) redshifted near the center of the granule and blueshifted near the edge of the granule.
D) blueshifted near the center of the granule and redshifted near the edge of the granule.

Answer 3

blueshifted near the center of the granule and redshifted near the edge of the granule.

Question 4

Which of these does NOT help to explain why the photosphere is called the visible surface of the Sun?

A) The photosphere marks an abrupt change in the Sun's density, which increases dramatically just below it.
B) Most of the visible light seen from the Sun originates within the photosphere.
C) Because of increased density below the photosphere, light originating there is unlikely to survive the journey out of the Sun.
D) The gas above the photosphere is too rarified to produce a significant amount of light.

Question 5

The Stefan-Boltzmann law indicates that the energy emitted per second per area of an emitting surface varies with the fourth power of the Kelvin temperature. Suppose the center of a granule on the Sun's photosphere is 6000 K and the edges of the cell are 100 K cooler. About how much energy is emitted each second from each unit area on the edge compared with that from the center?

A) 10^-8
B) 50%
C) 93%
D) 127%

Question 6

The photosphere of the Sun is the

A) visible "surface" of the Sun.
B) middle layer of the Sun's atmosphere.
C) region of convecting gases below the visible surface of the Sun.
D) core of the Sun, where the nuclear energy is generated.

Question 7

Granulation on the surface of the Sun is caused by

A) differential rotation of the Sun.
B) nuclear fusion processes occurring just below the surface.
C) magnetic field disturbances above the solar surface.
D) convective currents carrying heat from beneath the surface.

Question 8

The approximate temperature of the visible surface of the Sun is

A) 10,000 K.
B) 2000 K.
C) 4300 K.
D) 5800 K.

Question 9

The centers of the granular cells on the surface of the Sun appear to be brighter than the edges of the cells because

A) higher magnetic field strength at the centers condenses and heats the gases there.
B) the centers are composed of gases that are different from the gases that compose the edges.
C) gases at the centers are more transparent than gases at the edges, allowing astronomers to view deeper and hotter layers.
D) the centers are hotter than the edges.

Question 10

The granular appearance of the surface of the Sun is evidence of what phenomenon occurring in or on the Sun?

A) cells of thermonuclear fusion just under the visible surface
B) rapid rotation of the surface layers producing swirls of gas
C) concentration and heating of ionized gas by regions of high magnetic fields
D) convective motion under the solar surface

Question 11

If granulation on the Sun's surface is a result of convective motion below it, with material upwelling at cell centers and returning between the cells, what is the expected temperature distribution across a granular cell?

A) The center of the cell will be cooler than the edges.
B) The center of the cell will be hotter than the edges.
C) Alternate cell centers will be hot and cold, with the edges at an intermediate temperature.
D) The temperature will be uniform across the cell because the photosphere conducts heat readily.

Question 12

A typical granule on the surface of the Sun is

A) about 1000 km across and lasts for a few minutes.
B) a few thousand kilometers across and lasts for about two solar rotations.
C) about 30,000 km across and lasts for several hours.
D) only about 50 km across and cannot be seen from Earth without special equipment.

Question 13

What is the explanation for the bright cells of photospheric gases that make up the cellular granulation pattern seen on the visible surface of the Sun?

A) The cells are the base of a circulation pattern that extends from the photosphere to the outer corona.
B) The cells are regions of nuclear energy generation in the Sun's photosphere.
C) Each cell is a region of strong magnetic field, which compresses and heats the gas within it.
D) The cells are the tops of blobs of hot gas that have risen from the Sun's convective zone.

Question 14

The gas motions within granules on the solar surface are

A) upward in the centers of some cells and downward in the centers of others; the gas cools as it passes over the boundaries between cells.
B) upward in the bright cell centers and downward around the darker edges.
C) downward in the bright cell centers and upward around the darker edges.
D) almost nonexistent; the dark patterns represent a network of absorbing gases overlying the photosphere.

Question 15

The thickness of the photosphere, or the visible "surface" of the Sun, is

A) about 4000 km.
B) about 50,000 km.
C) about 1 km.
D) about 400 km.

Question 16

How does the average density of the Sun compare with that of the planet Jupiter?

A) It is not possible to specify an average density for an object as large as the Sun.
B) The Sun is many times denser than Jupiter.
C) The Sun is considerably less dense than Jupiter.
D) The Sun has approximately the same average density as Jupiter.

Question 17

If the temperature of the solar surface is 5800 K and Wien's law for the peak wavelength of the spectrum of the Sun, assumed to be a blackbody, is given by $\lambda$ _max T = 2.9*10⁶, with T in Kelvins and $\lambda$ in nanometers (nm), what is the expected peak wavelength of light from the Sun?

A) 600 nm
B) 500 nm
C) 300 nm
D) 50 nm

Question 18

The granulation observed on the photosphere of the Sun appears to be the result of

A) the Sun's magnetic field.
B) convection currents.
C) differential rotation.
D) optical effects caused by the turbulence in the Sun's atmosphere.

Question 19

What term is given to the visible "surface" of the Sun?

A) prominence
B) corona
C) chromosphere
D) photosphere

Question 20

What is the Sun's photosphere?

A) envelope of convective mass motion in the outer interior of the Sun
B) lowest layer of the Sun's atmosphere
C) middle layer of the Sun's atmosphere
D) upper layer of the Sun's atmosphere

Question 21

The center of the disk of the visible Sun appears brighter than the edges because one sees

A) less radiation from the cooler chromosphere near the edges of the Sun.
B) into deeper and hotter layers at the center of the solar disk.
C) into deeper and cooler layers at the center of the solar disk.
D) a greater contribution from the corona of the Sun at the center of the disk.

Question 22

A typical Doppler shift in the center of a granular cell compared to the "rest" wavelength is 8.75 *10^-4 nm. Take the rest wavelength to be the H_α line of 656 nm. What is the corresponding material speed in the center of the cell?

A) 0.4 m/s
B) 0.4 km/s
C) 8.75 m/s
D) 875 m/s

Question 23

Astronomers use the word "limb" to refer to what part of a celestial body?

A) edge
B) center
C) top
D) bottom

Question 24

Where is the chromosphere on the Sun?

A) The chromosphere is the outermost part of the Sun's atmosphere.
B) The chromosphere is the layer below the visible surface of the Sun, where convection begins.
C) The chromosphere is the visible surface of the Sun.
D) The chromosphere is the layer above the visible surface of the Sun.

Question 25

Where do spicules tend to occur on the Sun?

A) at the boundaries of supergranules
B) at the boundaries of granules
C) surrounding and between sunspots in sunspot groups
D) randomly over the surface of the Sun

Question 26

The surface of the Sun near its edge appears dimmer and cooler than at the center of the disk when viewed in visible light because one sees

A) deeper into the Sun near the edge than at disk, and temperature increases with depth.
B) light from the edge that has had to pass through more of the absorbing chromosphere and corona and is thereby reduced in intensity.
C) less deeply into the Sun near the edge than at disk center, and temperature decreases with depth.
D) less deeply into the Sun near the edge than at disk center, and temperature increases with depth.

Question 27

When viewing the Sun's disk in visible light, one sees less deeply into the Sun near the limb than at the center of the disk because of the interaction of the light with atoms of the gas. What conclusion can be drawn from the observation that the Sun appears less bright near the limb than it does at the disk center?

A) The light from the solar limb is redshifted because of solar rotation, and this phenomenon gives the appearance of cooler gas at the limb.
B) The temperature of the gas increases with increasing height in the solar atmosphere.
C) The light has to travel through more of the solar corona from the limb; hence, it is reduced in intensity and appears cooler.
D) The temperature of the gas falls with increasing height in the solar atmosphere.

Question 28

The visible light coming from the solar chromosphere is dominated by light of what color?

A) indigo
B) blue
C) green
D) red

Question 29

The Sun is about 1000 times more massive than the planet Jupiter. Why, then, does it have about the same average density as Jupiter?

A) The Sun has a much weaker gravitational field than Jupiter.
B) The Sun also has about 1000 times Jupiter's volume.
C) The Sun is rotating much faster than Jupiter, and the resulting centrifugal force helps to support the outer solar layers.
D) The Sun's solid core is composed of hydrogen, which is less dense than Jupiter's rocky core.

Question 30

If looking at the center of the Sun, one sees into the base of the photosphere at approximately 5800 K. If looking into the Sun nearer the edge, one might see as far as a layer above the base with a temperature of perhaps 5500 K. According to the Stefan-Boltzmann relation, what is the flux in the center of the solar disk compared to the flux near the edge?

A) 5500/5800 = 0.95
B) 5800/5500 = 1.05
C) (5800/5500)² = 1.11
D) (5800/5500)⁴ = 1.24

Question 31

Compared with the photosphere, the solar chromosphere is

A) less dense but with a greater vertical extent.
B) cooler and with a greater vertical extent.
C) denser but with a narrower vertical extent.
D) hotter and with a narrower vertical extent.

Question 32

What is a spicule on the Sun?

A) bright arc of gas suspended above the edge of the visible disk of the Sun
B) long, thin, curved line of bright gas in the corona
C) small, bright cell in the photosphere
D) jet of rising gas in the chromosphere

Question 33

What is the reason that the edge of the Sun's visible disk is darker than the center?

A) The gases near the edge are in regions where stronger magnetic fields inhibit the emission of light.
B) One sees more deeply into the Sun near its edge, and the gas is cooler at the deeper levels.
C) One sees into shallower layers of the Sun near the edge where the gas is cooler and so emits less light.
D) One sees into shallower layers of the Sun near the edge. Because the gas is less dense there, it emits less light.

Question 34

Until recent times, astronomers had to await a total solar eclipse to study the chromosphere. Why couldn't an observer hold a coin in front of them to cover the solar disk and create an artificial "eclipse" that would permit them to study the chromosphere?

A) Refraction of light around the coin will cause light from the photosphere to enter the observer's eye along with light from the chromosphere.
B) Light from the very rarified chromosphere is too weak to penetrate Earth's atmosphere.
C) Scattering by Earth's atmosphere will allow light from the photosphere to pass around the coin and enter the observer's eye.
D) Even with electronic equipment, it is not possible to hold the coin steady enough against the apparent motion of the Sun to view only the thin chromosphere.

Question 35

What is the name of the layer of the Sun's atmosphere that appears as a pinkish ring just outside the visible disk of the Sun during a total solar eclipse?

A) chromosphere
B) photosphere
C) convective zone
D) corona

Question 36

The word "chromosphere" refers to a

A) dense, spherical interstellar cloud of glowing gas.
B) layer in Earth's atmosphere just below the ionosphere.
C) layer in the Sun's atmosphere.
D) light-emitting region just outside the event horizon of a black hole.

Question 37

What causes limb darkening?

A) The photosphere at the edge of the Sun's surface is cooler than it is in the middle of the Sun's surface.
B) The limb of the Sun is darker than the center because sunspots collect along the limb.
C) Light reaching Earth from the limb of the Sun originates in the higher, cooler layers of the Sun.
D) Convection within the Sun is more efficient laterally than it is vertically with the result that the middle latitude regions of the Sun's surface are hotter than the poles.

Question 38

What are spicules?

A) small but rapidly erupting gas jets in the atmosphere of the Sun
B) gas streams in binary star systems, where a neutron star is pulling material from its companion star
C) streams of gas in interstellar clouds, heated by hot, massive stars
D) filamentary networks of hot gas in supernova remnants

Question 39

Spicules on the solar surface are

A) jets of gas surging out of the photosphere of the Sun into the chromosphere, usually at supergranule boundaries.
B) intense eruptions from sunspot groups and active regions, associated with solar flares.
C) streams of solar coronal material, usually seen only during a total solar eclipse.
D) curtainlike structures hanging over sunspot regions.

Question 40

What type of intensity distribution is seen across the image of the visible Sun from center to edge?

A) image with uniform distribution except where active regions occur
B) image of uniform brightness right to the limb
C) limb darkening
D) limb brightening

Question 41

To what extent do spicules cover the chromosphere?

A) The chromosphere is always completely covered by spicules.
B) Spicules cover most but not all of the chromosphere.
C) Spicules cover a few percent of the chromosphere.
D) Spicules are rare and only appear during the height of the solar cycle maximum.

Question 42

Which part of the Sun is the LEAST dense?

A) core
B) photosphere
C) chromosphere
D) corona

Question 43

How are spicules formed in the Sun's chromosphere?

A) Spicules are formed from material on the tops of granules "tossed" to higher altitudes by the oscillations of the Sun's surface.
B) Spicules are formed from gas carried upward along with the magnetic field lines at the edges of supergranules.
C) Spicules form where the Sun's twisted magnetic field lines break through the photosphere.
D) Spicules are the remnants or "stumps" of solar prominences that have broken free of the magnetic fields that confine them and have erupted out into space.

Question 44

Compared with the dimensions of a granule in the Sun's photosphere, a supergranule in the chromosphere is

A) very much larger; the diameter of each supergranule spreads across about a million granules.
B) a little larger, by a factor of 2.
C) much larger, by a factor of about 1000.
D) larger, by a factor of 10.

Question 45

What is a plasma?

A) material in which all the spectral lines exhibit Zeeman splitting
B) gas so dense that visible light will not penetrate it
C) state of matter consisting of electrons and ionized atoms
D) ring around the Sun's equator caused by magnetic effects

Question 46

What are the names of the three layers in the Sun's atmosphere, in order from lowest to highest distance from the center of the Sun?

A) corona, chromosphere, photosphere
B) photosphere, chromosphere, corona
C) photosphere, corona, chromosphere
D) chromosphere, photosphere, corona

Question 47

In order of increasing depth into the solar atmosphere, what are the names of the three layers of the Sun?

A) corona, chromosphere, photosphere
B) photosphere, chromosphere, corona
C) chromosphere, photosphere, corona
D) photosphere, corona, chromosphere

Question 48

What is the corona on the Sun?

A) Sun's inner atmosphere, just above the photosphere
B) large region beyond (outside of) the Sun's atmosphere, filled with solar wind
C) region above the solar north and south poles, the Sun's "crown"
D) Sun's outer atmosphere

Question 49

What is a plasma?

A) region where the H _$\alpha$ line causes the Sun's surface to glow red, like blood
B) region where the intense magnetic field has caused the Sun's atoms to line up in a rigid array
C) gaslike mixture of ions and electrons
D) unusual mixture of charged particles in which the positives and negatives do not occur in equal numbers

Question 50

What fraction of the Sun's total emission, across all wavelengths, is produced by the corona?

A) one part in a trillion
B) one part in a million
C) one percent
D) about one-third

Question 51

Many images of the chromosphere are taken through a filter that allows only specific wavelengths to pass. One reason for this is

A) to block out all other wavelengths of light and allow through the prominent light of these wavelengths produced in the chromosphere.
B) to allow through the filter the background light at these specific wavelengths produced by the photosphere and thus show an effective contrast with the chromosphere.
C) to ensure that Earth's atmosphere does not interfere with the image.
D) to block out light from the corona.

Question 52

What name is given to the outermost atmospheric layer of the Sun?

A) convective zone
B) radiative zone
C) corona
D) chromosphere

Question 53

Where is the coolest region in the Sun?

A) just below the photosphere, in the convective zone
B) in the lower corona
C) in the lower photosphere
D) in the lower chromosphere

Question 54

The typical speed of spicular material traveling outward from the photosphere in the direction of Earth is 20 km/s. What would be the observed wavelength of the Balmer H _$\alpha$ hydrogen spectral line emitted by this gas compared with that from stationary solar material?

A) There will be no shift since the light is emitted by hydrogen gas in both the spicule and the stationary solar material.
B) 0.044 nm longer than the H _$\alpha$ from stationary solar material
C) 0.000067 nm shorter than the H _$\alpha$ from the stationary solar material
D) 0.044 nm shorter than the H _$\alpha$ from stationary solar material

Question 55

A supergranule on the Sun is

A) a large area of slowly rising and falling gas containing hundreds of ordinary granules.
B) another name for a large, long-lived sunspot group.
C) a large area in which the rapid convection of the gas destroys all granules that would otherwise form in that area.
D) a very large but otherwise ordinary granule in the photosphere.

Question 56

Large regions of the Sun's chromosphere rise and fall vertically. These are called supergranules, and the boundaries of supergranules are marked by

A) vents.
B) sunspots.
C) spicules.
D) granules.

Question 57

What is surprising about the atmosphere of the Sun?

A) The pressure of the Sun's atmosphere, after dropping just above the photosphere, rises again to a value equivalent to that at the photosphere at the top of the chromosphere.
B) The density of the Sun's atmosphere, after falling rapidly above the photosphere, rises again significantly in the chromosphere.
C) The temperature of the Sun's atmosphere, after rising continuously from below the photosphere through the chromosphere, falls again suddenly in the corona.
D) The temperature of the Sun's atmosphere, after falling above the photosphere, rises again to reach very high values high in the atmosphere.

Question 58

Spicules in the chromosphere rise up from

A) the centers of sunspots.
B) the edges of granules.
C) the edges of supergranules.
D) random, constantly shifting locations on the photosphere.

Question 59

Which layer of the Sun's atmosphere has the greatest vertical thickness?

A) corona
B) chromosphere
C) photosphere
D) They are each about the same.

Question 60

What is the name of a small jet of rising gas in the chromosphere of the Sun?

A) flare
B) spicule
C) prominence
D) granule

Question 61

What is the "transition zone"?

A) This is the boundary where the temperature drops between the photosphere and the interior.
B) This is the boundary where the temperature drops again moving from the photosphere to the chromosphere.
C) This is the boundary where the temperature drops from the chromosphere to the cold of outer space.
D) This is where the temperature climbs sharply in moving from the chromosphere to the corona.

Question 62

How much mass will the Sun lose to space during its lifetime, through the solar wind?

A) a few thousandths of its total mass
B) only a few millionths of its total mass
C) well over one-half of its total mass
D) up to 25% of its total mass

Question 63

The total light emitted by the solar corona, which is seen MOST effectively during a total solar eclipse, is equivalent in brightness to

A) the average brightness of the night sky at a dark site.
B) the brightness of the full Moon, about one millionth as bright as the solar photosphere.
C) the average brightness of the Milky Way.
D) about one thousandth that of the solar photosphere.

Question 64

Why is the solar corona so much hotter than the photosphere?

A) Energy is carried upward through the chromosphere by disturbed and tangled magnetic fields.
B) The corona absorbs light from the photosphere very efficiently.
C) The density of the corona is low; following the laws of thermodynamics, the product of density and temperature is a constant.
D) Energy is carried upward through the chromosphere by convective gas motions.

Question 65

If the solar wind particles have speeds of 3 *10⁶ km/h, how long will it take for them to travel from the Sun to Earth?

A) 50,000 hours, or 2000 days
B) 5 hours, or less than 1/4 day
C) 0.5 hour, or about 30 minutes
D) 50 hours, or about 2 days

Question 66

The corona of the Sun has a temperature that is

A) about 10 K because it merges with cold interstellar space.
B) noticeably less than the photosphere, between 1000 to 2000 K.
C) about 1 to 2 million K.
D) about the same as the photosphere, about 6000 K.

Question 67

What is the solar wind?

A) constant flux of photons from the Sun's visible surface
B) material from the corona, accelerated out into space
C) storm of waves and vortices on the Sun's surface generated by a solar flare
D) circulation of gases in the chromosphere, between the equator and the poles of the Sun

Question 68

The temperature of the corona of the Sun is

A) very hot, about 10⁶ K.
B) about twice as hot as the photosphere, 12,000 K.
C) very cool because it is the farthest part of the Sun from the heat source.
D) about the same as that of the photosphere, 5800 K.

Question 69

The visible corona of the Sun is MOST effectively photographed

A) during lunar eclipses, when the sky is darker.
B) during solar eclipses.
C) over a period of a few years around times of maximum solar activity.
D) in spring and fall seasons because of the tilt of the spin axis of the Sun.

Question 70

One particular feature of the solar corona is its

A) variation with time over periods of a few minutes.
B) very high temperature.
C) very uniform density and structure.
D) very cold temperature.

Question 71

The bright X-ray image obtained of the solar corona when the Sun is photographed at this wavelength indicates that the gas temperature at these heights is

A) extremely high, above 10⁶ K.
B) extremely low, much cooler than the photosphere.
C) about twice that of the photosphere.
D) about the same temperature as the photosphere.

Question 72

The extremely high gas temperatures in the solar corona mean that this region is BEST observed at wavelengths of

A) X-rays.
B) visible light.
C) Balmer H _$\alpha$ light from hydrogen gas.
D) infrared light.

Question 73

Where would one expect to find heavy atoms like iron stripped of many of their electrons?

A) photosphere
B) chromosphere
C) corona
D) sunspots

Question 74

Which occurrence led astronomers to the conclusion that the temperature of the gases in the solar corona is very high?

A) detection of emission lines from highly ionized elements like iron
B) measurement of the brightness and spectrum of the continuum visible light from the corona during eclipses
C) direct measurements using space probes exploring the corona
D) observation of the effect of these gases on the planets Mercury and Venus

Question 75

The energy source that heats the low-density coronal gas to extremely high temperatures is MOST likely

A) conduction because the chromosphere and corona contain high densities of free electrons that facilitate conduction.
B) rearrangements within complex magnetic field structures that energize the ionized gas.
C) convective currents in the chromosphere that carry hot gas outward from the photosphere.
D) radiative heat from the photosphere that is strongly absorbed by highly ionized atoms such as Fe XIV.

Question 76

What is the temperature of the solar corona?

A) 50,000 to 100,000 K
B) 2000 to 3000 K
C) 5800 K
D) 1 to 2 million K

Question 77

What is the source of the X-rays emitted by the solar corona?

A) high-energy charged particles spiraling along the coronal magnetic fields
B) X-rays from the solar photosphere, scattered by ions in the corona
C) decay of radioactive nuclei in the coronal gases
D) high-temperature gas of the corona

Question 78

The spectrum of the solar corona reveals emission lines that originate in atoms from which many electrons have been stripped. What conclusion can be drawn from this result?

A) The magnetic field intensity is high enough to drag electrons from the atoms.
B) The solar rotation speed at coronal height reduces the ability of atoms to retain electrons.
C) The pressure of the gas is sufficient to squeeze the electrons from the atoms.
D) The atomic collision energies and hence the gas temperatures are extremely high.

Question 79

Which of these features appears in the spectrum of the solar corona and indicates very high gas temperatures?

A) intense emission lines from highly ionized atoms, such as iron
B) bright emission from the hydrogen Balmer line, H _$\alpha$ , at the red end of the spectrum
C) intense continuous emission in the infrared part of the spectrum
D) dark absorption lines from hydrogen, calcium, and iron on a continuous bright spectrum

Question 80

To what does the symbol Fe XIV refer?

A) compound of iron, xenon, iodine, and vanadium
B) iron atoms that have lost 15 electrons
C) iron atoms that have lost 14 electrons
D) iron atoms that have lost 13 electrons