Deck 9: The Sun: Our Extraordinary Ordinary Star

Question 1

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.

Answer 1

visible "surface" of the Sun.

Question 2

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

Answer 2

convective motion under the solar surface

Question 3

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.

Answer 3

upward in the bright cell centers and downward around the darker edges.

Question 4

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

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

Question 5

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 us to view deeper and hotter layers.
D) the centers are hotter than the edges.

Question 6

Why is the photosphere called the visible surface of the Sun? Each of the statements below is a partial answer to this question EXCEPT ONE.Which is the exception?

A) The photosphere is indeed a surface with nothing above it and an abrupt density increase just below it.
B) Most of the visible light we see 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 7

What is the Sun's photosphere?

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

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

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 10

The brighter cells surrounded by dark,narrow boundaries making up the cellular pattern that completely covers the visible surface of the Sun are called:

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

Question 11

The temperature of the Sun's photosphere is:

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

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

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

Question 14

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 15

If you look at the center of the Sun,you see into the base of the photosphere at approximately 5800 K.If you look into the Sun nearer the edge,you 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 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

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

Question 18

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 19

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 20

A typical Doppler shift in the center of a granular cell compared to the "rest" wavelength is 8.75 X 10-⁴ nm.Take the rest wavelength to be the Hα 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 21

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

Question 22

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

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

Question 23

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 24

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 25

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 26

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

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

Question 27

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

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

Question 28

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.

Question 29

When we view the Sun's disk in visible light,we see 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 30

The photosphere emits far more radiant energy than does the chromosphere above it.How is it possible to image just the chromosphere from Earth?

A) It is necessary to wait for a solar eclipse during which the Moon just blocks the photosphere, leaving the edges of the chromosphere visible.
B) It is not necessary to wait for a natural eclipse. Standing on Earth's surface, it is possible to create an artificial eclipse just by holding a coin at the appropriate distance to cover the photosphere and leave the chromosphere's edges visible.
C) The photosphere emits a great deal of Hα radiation, while the chromosphere does not. So one images the chromosphere through a filter that blocks Hα.
D) The photosphere emits very little Hα radiation, while the chromosphere emits a great deal. So one images the chromosphere through a filter that passes Hα.

Question 31

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 us 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 32

The Sun is about a thousand 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 a thousand 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 33

What is a spicule on the Sun?

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

Question 34

Many images of the chromosphere are taken through a red filter.One reason for this is to:

A) block out all red light and allow through the prominent light of other colors produced in the chromosphere.
B) allow through the filter the red light produced by the photosphere and thus show an effective contrast with the chromosphere.
C) ensure that the blue of Earth's atmosphere does not interfere with the image.
D) allow through the red light which is produced predominantly in the chromosphere and not in the photosphere.

Question 35

The center of the disk of the visible Sun appears brighter than the edges because we see:

A) less radiation from the cooler chromosphere near the edges of the Sun.
B) into deeper and hotter layers at the center of the 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 36

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 37

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 we see:

A) deeper into the Sun near the edge than at disk center 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 38

Until recent times,astronomers had to await a total solar eclipse to study the chromosphere.Why do suppose you cannot hold a coin in front of you to cover the solar disk and create an artificial eclipse that will permit you to study the chromosphere?

A) Refraction of light around the coin will cause light from the photosphere to enter your 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 your 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 39

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) We see more deeply into the Sun near its edge, and the gas is cooler at the deeper levels.
C) We see into shallower layers of the Sun near the edge, where the gas is cooler and so emits less light.
D) We see into shallower layers of the Sun near the edge; because the gas is less dense there, it emits less light.

Question 40

The photosphere is cooler than the chromosphere.How does this influence the spectral characteristics of the Hα line,the prominent red line in the hydrogen spectrum?

A) This line is an emission line in the chromosphere but an absorption line in the photosphere.
B) This line is an absorption line in the chromosphere but an emission line in the photosphere.
C) Both the chromosphere and the photosphere show absorption lines for Hα, but the lines are darker and broader in the chromosphere.
D) Both the chromosphere and the photosphere show absorption lines for Hα, but the lines are darker and broader in the photosphere.

Question 41

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 42

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

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

Question 43

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 44

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) curtain-like structures hanging over sunspot regions.

Question 45

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 plasma 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 46

Large regions of the Sun's chromospheres 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 47

What is the corona on the Sun?

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

Question 48

The HIGHEST temperatures in the Sun are found in the:

A) corona.
B) chromosphere.
C) photosphere.
D) solar interior.

Question 49

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 50

What name is given to the outer atmosphere of the Sun?

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

Question 51

Figure 9-5 in Comins,Discovering the Essential Universe,6th ed.,shows an image taken through a filter that passes the red Hα hydrogen line and blocks other wavelengths.Why does this image show the chromosphere but not the photosphere?

A) The chromosphere is cooler than the photosphere and therefore emits Hα, while the warmer photosphere does not.
B) The chromosphere is warmer than the photosphere and therefore emits Hα, while the cooler photosphere does not.
C) The photosphere lacks hydrogen and therefore cannot emit Hα.
D) The Hα emitted by the photosphere is blocked by the chromosphere.

Question 52

Where would you expect to find spicules?

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

Question 53

Which part of the Sun is the LEAST dense?

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

Question 54

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 55

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 56

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 57

A visible light spectrum of the Sun reveals many dark absorption lines.These lines are caused by photon absorption,which takes place in the:

A) corona.
B) photosphere.
C) sunspot groups.
D) solar interior.

Question 58

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 59

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 60

To what extent do supergranules cover the chromoshpere?

A) The chromosphere is always completely covered by supergranules.
B) Supergranules cover most but not all of the chromospheres.
C) At any one time, a few hundred supergranules exist and cover a few percent of the chromospheres.
D) Supergranules are rare and only appear during the height of the solar cycle maximum.

Question 61

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

Question 62

Which was NOT a finding of the Genesis spacecraft mission?

A) The solar wind has a tail of solar wind gases that extends outside the heliosphere.
B) The isotope abundances in the solar wind and in Earth's atmosphere are not identical.
C) Neon in layers under the Moon's surface have been altered by being bombarded by radiation from space.
D) The Sun has maintained a relatively constant temperature for a long period.

Question 63

Which feature 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, Hα, 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 64

Which occurrence led astronomers to the conclusion that the temperature of the gases in the solar corona was 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 65

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 66

Other stars:

A) have never been detected producing a solar wind.
B) produce their own solar winds, but these are too weak to reach the vicinity of the solar system.
C) produce their own solar winds, but most are prevented from reaching the planetary region of our solar system by our Sun's heliosphere.
D) produce their own solar winds, and these galactic cosmic rays contribute the bulk of the cosmic ray flux we receive on Earth.

Question 67

What is the solar wind?

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

Question 68

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

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

Question 69

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 70

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 71

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 chromospheres to the cold of outer space.
D) This is where the temperature climbs sharply in moving from the chromosphere to the corona.

Question 72

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 73

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 74

The heliosphere:

A) is spherical.
B) is mostly within the orbit of Mercury.
C) is the limit for solar wind gases moving out beyond the Sun.
D) involves an interaction of the solar wind and the solar magnetic field.

Question 75

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 76

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 77

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 78

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 79

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 80

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.