Chapter 16 + 17 review

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 line of 656 nm. What is the corresponding material speed in the center of the cell?

.4 km/s

What is the temperature of the solar corona?

1-2 million K

Solar magnetic activity at the present time in history seems to vary almost periodically with a time scale of

22 years

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?

50 hours, or about 2 days

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 max T = 2.9 × 106 , with T in Kelvins and in nanometers (nm), what is the expected dominant wavelength of the Sun?

500 nm

The approximate temperature of the visible surface of the Sun is

5800 K

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 granulation (convection cell) 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?

93%

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

Convective motion under the solar surface

Which of the following astronomers was the first to detect the rotation of the Sun by watching sunspot motions?

Galileo

How large is a typical sunspot?

It is about the size of Earth

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

Its very powerful magnetic field

Why should you never look directly at the Sun?

Looking directly at the Sun causes blindness.

A model was proposed in 1960 by Horace Babcock to explain the solar cycle. This model bears the name

Magnetic Dynamo

Differential rotation has been observed on three of the following bodies. On which has differential rotation not been observed?

Mars

What is the character of the sunspot cycle?

Starting at sunspot minimum, spots first appear far from the equator, followed by new spots appearing closer to the equator as they increase in number, then die out close to the equator.

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

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.

The magnetic field in a large rotating body can reverse direction periodically. For which two bodies in the solar system has evidence been found for such magnetic reversals?

Sun and Earth

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

Sunspots occur in regions of lower than average magnetic fields

To make an image of the chromosphere without the much brighter light from the photosphere, a filter which allows the hydrogen H line to pass is often used. Why?

The H line is produced in the protosphere but it is also absorbed, so only a dark absorption line results.

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?

The center of the cell will be hotter than the edges

Where is the chromosphere on the Sun?

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

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?

The light from the umbra is redder

How would you describe the Sun's rotation?

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

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 incorrect. Which one is the exception?

The protosphere is indeed a surface with nothing above it and an abrupt density increase just below it

An astronomer observing certain regions of the Sun through a spectrometer notices that the spectral lines emitted from these regions are split into two or more components. What does the astronomer conclude about these regions from his observations?

The regions contain strong magnetic fields

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

The sun's overall energy output depends on the 11 year sunspot cycle

If a solar flare produces an X-ray outburst and also triggers a coronal mass ejection (CME), what will be the arrival times of these components, referenced to the time of occurrence on the Sun?

The x rays arrive about 8 minutes after the flare, while the CME material arrives after about 2 days

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

This line is an emission line in the chromosphere but an absorption line in the photosphere

Over the course of a sunspot cycle of about 11 years, the regions of sunspot occurrence on the Sun move

Toward the equator, moving from 30 degrees to 10 degree latitude

The Gas Motions Within Granules On The Solar Surface Are

Upward in the bright cell centers and downward round the darker edges.

Intense magnetic fields have been found to exist in sunspots by the observation of what specific physical effect?

Zeeman effect, the splitting of spectral absorption lines

What is a plage?

a bright area in the chromosphere

What is a plasma?

a gas-like mixture of ions and electrons

A supergranule on the Sun is

a large area of slowly rising and falling gas containing hundreds of ordinary granules.

The corona of the Sun has a temperature that is

about 1 to 2 million K.

The total time the Sun will spend converting hydrogen to helium in its core is

about 10 billion years

In terms of its total hydrogen-burning lifetime, the Sun is

about halfway through its life

Sunspots appear dark because they

are cooler than the surrounding surface.

Where would you expect to find spicules?

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

A solar plage is 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.

Coronal mass ejections have all of the following characteristics except one. Which is the exception?

cease during the years of solar minimum

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

convection currents

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

convection motion of gases in the upper portion of the sun's interior

How does a coronal hole compare with the rest of the solar corona?

cooler and darker coro

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

corona

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

corona

Which part of the Sun is the least dense?

corona

The solar wind appears to originate mainly from which regions of the Sun?

coronal holes

X-ray observations of the corona reveal lighter and darker spots, the latter indication where the coronal is cooler. These darker spots are the source of

coronal mass ejections

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

detection of emission ines from highly ionized elements like iron

The visible corona of the Sun is most effectively photographed

during solar eclipses

The solar wind is almost entirely ionized gas

escaping through coronal holes.

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

extremely high-temperature gas

The rotation of the Sun is

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

What name is given to an irregular dark line or streak often seen in H photographs of the solar photosphere, often associated with sunspots?

filament

What process provides the power to maintain the Sun's radiative output?

fusion of hydrogen into helium

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

granules

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

high precision doppler shifts of spectral lines

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

high-temperature gas of the corona

Solar flares, the violent eruptive events on the Sun, occur most frequently

in or above complex sunspot groups

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

intense emission lines from highly ionized atoms, such as iron

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

into deeper and hotter layers at the center of the disk

What is a spicule on the Sun?

jet of rising gas in the chromosphere

What is a prominence on the sun?

large loop of gas supported by magnetic fields

The word chromosphere refers to a

layer in the Sun's atmosphere.

Compared with the photosphere, the solar chromosphere is

less dense but with a greater vertical extent

How long does a typical flare on the Sun last?

less than an hour

What causes limb darkening?

light reaching us from the limb of the sun originates in the higher, cooler layers of the sun

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

limb darkening

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

major hurricane

Galileo observed the phenomenon of solar rotation in the early 1600s by

measuring the motion of sunspots across the solar surface

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

much larger, by a factor of about 1000

The heliosphere is a bubble in space defined by the outflow of the solar wind. A recent discovery of the solar wind is that it is

not spherical

Where on the Sun do solar flares occur?

only within sunspot groups

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

photosphere

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

photosphere, chromosphere, corona

What name is given to a brighter region in the chromosphere, often in association with a sunspot?

plage

Just before a sunspot forms on the photosphere, we will often see at that location

plages

Other Stars

produce their own solar winds, but most are prevented by our sun's heliosphere from reaching the planetary region of our solar system

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

prominence

What is a filament on the Sun?

prominence seen in silhouette against the photosphere

The heliosphere is the

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.

We have orbiting satellites that continually monitor the Sun. These observations take place in all regions of the electromagnetic spectrum except

radio

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

red

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

regular 5-minute oscillations and fluctuations of the surface

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?

scattering by earth's atmosphere will allow light from the photosphere to pass around the coin and enter your eye

The highest temperatures in the Sun are found in the

solar interior

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

spicules

What is the solar wind?

the Sun's outer atmosphere streaming out into space

. How does the number of sunspots on the Sun vary with time?

the number of sunspots varies relatively regularly, with a period of about 11 years

Hydrogen "burning" by fusion reactions occurs only in the deep interior of the Sun (and other stars) because

the requisite conditions of high temperature and high density occur only there

In the 1920s, Arthur Eddington made a proposal that proved vital to showing how stars generate energy. This was that

the sun's core is much hotter than previously thought

The photosphere of the Sun is the

the visible surface of the sun

The reason sunspots are cooler than the photosphere is that

their powerful magnetic fields inhibit the convective flow of the ionized gases of the photosphere

What is the energy source for the Sun?

thermonuclear fusion in the core

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

to allow through the filter the red light produced by the photosphere and thus show an effective contrast with the chromosphere

What is nuclear fusion?

two nuclei sticking together to form a new, heavier nucleus

One particular feature of the solar corona is its

very high temperature

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

we see into shallower layers of the sun near the edge where the gas is cooler and so emits less light

The polarity of the Sun's magnetic field reverses during a sunspot cycle. When does this reversal take place?

when the sunspot number is maximum, about every 11 years