Astronomy Chapter 10 HW Questions

The Sun doesn't have a perfect blackbody spectrum because (a) its spectrum consists of emission lines of elements in the Sun, so there are some gaps; (b) its core is much hotter than its surface, so the shape of the curve it distorted; (c) the coronal mass ejections interfere with the photons, adding too much noise to the spectrum; (d) the Sun is too hot to radiate at all wavelengths; (e) the relatively cool outer layers absorb photons emitted in the hot inner parts of the Sun, producing absorption lines. (Textbook, 4th edition, question 36, p. 276.)

(e) the relatively cool outer layers absorb photons emitted in the hot inner parts of the Sun, producing absorption lines.

Large groups of sunspots can be relatively long-lived (a few months), and they remain essentially fixed at the same physical location on the photosphere throughout their lives. Suppose a sunspot group appears to move from the center to the edge (limb) of the Sun's disk in 7 days. What is the approximate rotation period of the Sun? (A rough estimate will suffice; don't worry about not being able to see the sunspot if it is exactly at the edge of the Sun.) (Textbook, 4th edition, question 14, p. 275.) Using the data in the question above, the rotation period of the Sun is _____ days (enter a whole number in the blank).

28

True or False? If a dark sunspot could be viewed alone, without the glare of the surrounding photosphere, it would still appear quite dark because it emits very little light.

False

True or False? It is safe and easy to view sunspots on a bright sunny day with the naked eye, without filters or other equipment.

False

True or False? The Sun's corona can typically be seen by blocking our view of the Sun's photosphere, for example with a coin.

False

True or False? The temperature of the Sun decreases from its core to the photosphere and out through the corona.

False

Layer 1: "The spectrum of the solar ( corona / chromosphere / photosphere ), like that of almost all stars, is a continuous spectrum crossed by absorption lines" (textbook, p. 259, emphasis added). Layer 2: "The Sun's ( corona / chromosphere / photosphere ) ... shows an emission line spectrum rather than absorption lines, since the gas is silhouetted against the dark sky rather than against the bright photosphere" (textbook, p. 274). Layer 3: Visible light from the solar ( corona / chromosphere / photosphere ) (Layer 3) shows three spectral components: continuous radiation, absorption lines, and emission lines. The spectrum of Layer 3 of the Sun differs from that of Layer 1 because Layer 1 never shows emission lines.

Layer 1: Photosphere Layer 2: Chromosphere Layer 3: Corona

True or False? During times of sunspot maxima, an unusually large number of prominences, solar flares, and coronal mass ejections also occur on the Sun.

True

True or False? The solar activity cycle has a period of about 22 years, including the magnetic pole reversal.

True

In the few days after a powerful solar flare, we might expect to see _______ at night in Earth's atmosphere.

auroras

Suppose the temperature of a sunspot is 4,000 K and that of the surrounding photosphere is about 6,000 K. What is the ratio (sunspot to photosphere) of the wavelengths at which the roughly blackbody spectra are brightest? (Hint: see Chapter 2.) (a) 2/3. (b) 3/2. (c) (2/3) 2. (d) 3. (e) 2,000. (Textbook, 4th edition, question 33, p. 276.)

b) 3/2

Which of the statements below are actual observations that indicate that the solar corona is very hot (about 2 million K near the Sun)? We know that the corona is hot _______. Choose two answers. • by measuring the speed of the solar wind. • because coronal emission lines indicate the presence of molecular hydrogen and atomic helium. • because coronal emission lines indicate the presence of extremely-ionized iron. • from the configuration of the Sun's magnetic field. • because the solar corona emits mainly in the infrared range. • because the solar corona emits mainly in the x-ray range.

because coronal emission lines indicate the presence of extremely-ionized iron. because the solar corona emits mainly in the x-ray range.

The ______ is the middle layer of the Sun's atmosphere; it is easily imaged if a hydrogen-light filter is used. It appears as a pinkish rim around the Moon during a solar eclipse.

chromosphere

The element helium was first identified in the spectrum of the solar ( corona / chromosphere / photosphere ).

chromosphere

A boiling, bubbling layer of the Sun's interior.

convective zone

This is the innermost, hottest, densest part of the Sun. Here vast quantities of energy are produced by nuclear fusion.

core

The ______ is the outermost part of the solar atmosphere; its tenuous, ionized gases are shaped into loops and streamers by the Sun's magnetic field.

corona

A(n) ______ is an enormous explosion of matter and energy from the Sun's corona.

coronal mass ejection

Suppose the temperature of a sunspot is 4,000 K and that of the surrounding photosphere is about 6,000 K. Per unit area, about how much energy per second does the sunspot emit compared with the photosphere? (Hint: see Chapter 2.) (a) 2/3. (b) 3/2. (c) 2,000. (d) (2/3) 2. (e) (2/3) 4. (Textbook, 4th edition, question 34, p. 276.)

e) (2/3)^4

There are two types of solar wind: ( hot / dense / fast ) solar wind and (cool / tenuous / slow ) solar wind. The (cool / tenuous / slow ) solar wind results simply from the expansion of coronal gases out into space. This type of solar wind takes about ( 1 / 5 / 10 / 20 ) day(s) to reach the Earth. In contrast, the ( hot / dense / fast ) solar wind, which travels about twice as fast (or faster), originates at (loops and streamers / coronal holes / prominences ) which are relatively ( hot / cool ) and (less dense / more dense ) parts of the Sun's corona. We on Earth are concerned with ( loops and streamers / coronal holes / prominences ) because the ( hot / dense / fast ) solar wind can produce ( granulation / spicules / magnetic storms ).

fast slow slow 20 fast coronal holes cool less dense coronal holes fast magnetic storms

Dark lines threading their way across the Sun, visible in H-alpha light near sunspots are _______.

filaments

According to this theory, the presence of a large mass curves space-time. Light travelling in curved space-time tends to curve toward large masses ("fall into the dents" in space-time).

general theory

During a total solar eclipse in 1919, light from a star positioned on the limb of the Sun was observed to be shifted away from the Sun by an amount predicted by this theory.

general theory

The gradual precession of Mercury's orbit provided a test of this theory.

general theory

This theory explains gravity and deals with accelerations.

general theory

______ is a feature that gives the Sun's surface a "salt-and-pepper" texture. It results from underlying convection in the Sun.

granulation

By far the most abundant element in the Sun is ________.

hydrogen

The magnetic field of the Sun shapes coronal gases into ________.

loops and streamers

If the corona is so much hotter than the photosphere, why isn't it much brighter than the photosphere, per unit area? (Textbook, 4th edition, question 9, p. 275.) The corona is less bright than the photosphere because the gas in the corona has a very (low / high) density.

low

The lowest layer of the Sun's atmosphere is called the _____; the light we receive from the Sun comes from this layer.

photosphere

A(n) _______ is a filament on the visible edge of the Sun; it projects out into space.

prominence

In this part of the solar interior, energy is transferred by radiation.

radiative zone

A(n) ______ is a huge eruption of material from the Sun's surface.

solar flare

As the solar atmosphere expands outward from the Sun, into interplanetary space, it becomes the ______.

solar wind

This theory assumes that the speed of light is an important constant that cannot be exceeded by real objects.

special theory

This theory is used to describe the motion of objects moving at nearly the speed of light.

special theory

______ are jets of gas within the chromosphere that have been compared in appearance to a burning prairie.

spicules

A(n) _______ is a region of the solar surface that is dark and relatively cool; it has an extremely high magnetic field.

sunspot

The Maunder minimum was a period in beginning in the mid-17th century when there were apparently no _________.

sunspots