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astronomy > chapter 1 > Flashcards

chapter 1 Flashcards

1
Q

What is the Sun’s photosphere?

A

lowest layer of the Sun’s atmosphere

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2
Q

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

A

convective motion under the solar surface

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3
Q

The heliosphere is the

A

protective region containing the Sun and planets created by the solar wind, which prevents penetration by much of the radiation from outside the solar system.

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4
Q

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 tops of blobs of hot gas that have risen from the Sun’s convective zone.

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5
Q

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

A

convection currents

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6
Q

The gas motions within granules on the solar surface are

A

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

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7
Q

Compared with the photosphere, the solar chromosphere is

A

less dense but with a greater vertical extent

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8
Q

Where is the chromosphere on the Sun?

A

The chromosphere is the layer above the visible surface of the Sun.

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9
Q

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

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10
Q

Where would you expect to find spicules?

A

as small but rapidly erupting gas jets in the atmosphere of the Sun

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11
Q

Where is the coolest region in the Sun?

A

in the lower chromosphere

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12
Q

What is surprising about the atmosphere of the Sun?

A

The temperature of the Sun’s atmosphere, after falling above the photosphere, rises again to reach very high values high in the atmosphere.

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13
Q

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

A

high-temperature gas of the corona

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14
Q

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 atomic collision energies and hence the gas temperatures are extremely high

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15
Q

To what does the symbol Fe XIV refer?

A

iron atoms that have lost 13 electrons

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16
Q

What is the temperature of the solar corona?

A

1 to 2 million K

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17
Q

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.

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18
Q

What is the solar wind?

A

material from the corona, accelerated out into space

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19
Q

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.

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20
Q

Astronomers have compared the relative abundances of different isotopes of neon found in Moon rocks with those found in the solar wind. What conclusion have they drawn?

A

The Sun has maintained a much more constant temperature than was previously believed.

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21
Q

Sunspots are

A

cooler, darker regions on the Sun’s surface

22
Q

What is the structure of a typical large sunspot?

A

dark center surrounded by a less dark area

23
Q

Sunspots appear dark because they

A

are cooler than the surrounding surface.

24
Q

The umbra of a sunspot is about 1500 K cooler than the surrounding solar photosphere. How does the light from the umbra compare with the light from the rest of the photosphere?

A

The light from the umbra is redder

25
Q

The average sunspot group on the solar surface will last for about

A

two rotations of the Sun

26
Q

The rotation of the Sun is

A

fastest at the equator, slower at mid-latitudes, and slowest near the poles.

27
Q

The equatorial regions of the Sun are seen to rotate with an approximate period of about

A

25 days

28
Q

Which one of the following statements about sunspots is NOT true?

A

Sunspots occur in regions of lower-than-average magnetic fields

29
Q

What is a plasma?

A

state of matter consisting of electrons and ionized atoms

30
Q

How would you describe the Sun’s rotation?

A

The outer layers of the Sun experience differential rotation, but the inner regions rotate as a solid body.

31
Q

What is a typical magnetic field strength inside a sunspot?

A

a few thousand times stronger than Earth’s magnetic field

32
Q

The major feature that distinguishes a sunspot from other regions on the Sun is

A

its very powerful magnetic field.

33
Q

The differential rotation of the Sun causes the magnetic fields in its interior to become tangled. According to the Babcock model of the solar activity cycle, what happens to these tangled magnetic fields?

A

The tangled magnetic fields interrupt the convection currents and trap gas. The gas rises, carrying the fields with it, and float to the Sun’s photosphere, where they break through and form sunspot groups.

34
Q

Two pairs of associated sunspots appear on the visible disk of the photosphere of the Sun, one pair in each hemisphere. If the magnetic polarity of the westernmost spot in the northern hemisphere is found to be N, what will be the magnetic polarities of the other three spots?

A

The magnetic polarity of the other northern spot will be S, while in the southern hemisphere the westward spot will be S and the eastward spot will be N

35
Q

What is helioseismology?

A

study of vibrations in the Sun’s interior

36
Q

Which recently discovered fact about the Sun might have some bearing on climate changes and the weather on Earth?

A

The Sun’s overall energy output depends on the 11-year sunspot cycle.

37
Q

What causes sunspots?

A

Magnetic fields breaking through the photosphere inhibit gas motion where the field is strong.

38
Q

What is the cause of the sunspot cycle on the Sun?

A

Subsurface magnetic fields are twisted by the Sun’s differential rotation and break through the surface as sunspots, then gradually cancel each other and return below the surface.

39
Q

What measurements first showed the 5-minute oscillations of the Sun’s surface?

A

high-precision Doppler shifts of spectral lines

40
Q

One method that has been used successfully in recent times to investigate the deep interior of the Sun has been to observe

A

regular 5-minute oscillations and fluctuations of the surface

41
Q

Which of the following phenomena is NOT a characteristic of the peak period in the solar activity cycle?

A

increased surface temperature on the Sun and a measurable increase in the temperature of Earth’s atmosphere

42
Q

A solar plage is a

A

brightening of a portion of the Sun in light from hydrogen and other atomic species, appearing just before a sunspot and then surrounding it.

43
Q

What causes plages?

A

compression and heating of chromospheric gas by magnetic fields

44
Q

An arching column of gas suspended over a sunspot group is called a

A

prominence

45
Q

What is a filament on the Sun?

A

prominence seen in silhouette against the photosphere

46
Q

What is a prominence on the Sun?

A

large loop of gas supported by magnetic fields

47
Q

Where on the Sun do solar flares occur?

A

only within sunspot groups

48
Q

Which of the following events is NOT a consequence of a coronal mass ejection event from the Sun that is aimed toward Earth?

A

major hurricane

49
Q

The solar wind is almost entirely ionized gas

A

escaping through coronal holes.

50
Q

Coronal holes are thought to be the source of

A

the solar wind

astronomy (3 decks)

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