l>Chapter 16, thing Review


A star is a glowing sphere of gas organized together by its own gravity and also powered by nuclear fusion at its center. The main internal regions the the Sun space the core, whereby nuclear reactions generate energy, the radiation zone, wherein the power travels exterior in the form of electromagnetic radiation, and the convection zone, where the Sun"s matter is in constant convective motion.

The sharp solar disk clearly shows from planet marks the solar photosphere—the thin surface ar layer native which the Sun"s irradiate is emitted. Above the photosphere lies the chromosphere, which is separated native the solar corona by a thin transition zone in i beg your pardon the temperature boosts from a couple of thousand to approximately a million kelvins.

The Sun"s luminosity is the total amount of power radiated native the solar surface per second. That is determined by measure the solar constant—the amount of solar radiation reaching each square meter in ~ Earth"s street from the Sun—and multiplying the amount through the area of an imaginary sphere of radius 1 A.U.

The mathematical version that ideal fits the it was observed properties that the sun is the Standard Solar Model. Studies of helioseismology—oscillations the the solar surface brought about by sound waves in the interior—provide additional insight right into the Sun"s structure.

The effect of the solar convection zone have the right to be checked out on the surface in the form of granulation of the photosphere. As hotter, and therefore brighter, gas rises and also cooler, dimmer gas sinks, a characteristic "mottled" figure results. Lower levels in the convection zone likewise leave their note in the form of larger patterns called supergranulation.

Most of the absorption lines watched in the solar spectrum are developed in the upper photosphere and the chromosphere. Researches of these enable scientists to determine the Sun"s composition and the temperature structure of the solar atmosphere.

At around 10—15 solar radii, the gas in the corona is hot sufficient to escape the Sun"s gravity, and the corona begins to circulation outward as the solar wind. Most of the solar wind operation from low-density regions of the corona dubbed coronal holes.

The stable component the the Sun"s energy production is known as the quiet Sun. Superimposed on that is the much more erratic emissions of the active Sun. Solar task is generally connected with disturbances in the Sun"s magnetic field. Sunspots space Earth-sized areas on the solar surface ar that are a tiny cooler 보다 the bordering photosphere. They are areas of extreme magnetism.

Both the numbers and locations that sunspots vary in one 11-year sunspot cycle. At solar minimum, just a couple of spots are typically seen, and they lie far from the solar equator. In ~ solar maximum, the variety of spots is lot greater, and also they normally lie much closer to the equator. The sunspot bicycle is fairly irregular. Its length varies native 7 come 15 years. There have been time in the past once no sunspots were seen for lengthy periods. The in its entirety direction the the solar magnetic ar reverses indigenous one sunspot cycle to the next. The 22-year cycle that results when the direction that the field is taken right into account is dubbed the solar cycle.

Solar task tends to be concentrated in active regions connected with sunspot groups. Prominences space loop- or sheetlike structures produced when hot gas ejected by activity on the solar surface ar interacts through the Sun"s magnetic field. The much more intense flares space violent surface ar explosions the blast particles and radiation right into interplanetary space.

The sun generates power by "burning" hydrogen right into helium in its main point by the procedure of nuclear fusion. Nuclei are held together by the strong nuclear force. When four protons overcome their electromagnetic repulsion and also are converted right into a helium cell nucleus in the proton-proton chain, part mass is lost. The law of conservation of mass and energy calls for that this mass appear as energy, eventually resulting in the light us see. Really high temperatures are needed for combination to occur.

Some particles developed during the solar combination process space the positron, or anti-electron, which easily annihilates v electrons in the Sun"s core to create gamma rays, the deuteron, one isotope the hydrogen consist of of a proton and a neutron, and the neutrino, a near-massless particle that escapes from the sunlight without any further interactions as soon as it is produced in the core. Neutrinos connect via the weak atom force.

Despite their elusiveness, that is feasible to detect a small portion of the neutrinos streaming from the Sun. The observations result in the solar neutrino problem—substantially fewer neutrinos are observed than are predicted by theory. The resolution to this trouble is unclear. A leading explanation is the neutrino oscillations convert some neutrinos right into other (undetected) particles en route from the sun to Earth.



You are watching: Why does the sun appear to have a sharp edge

The sunlight is a quite normal star. (Hint)

2. The Sun"s average density is greater than that of Earth. (Hint)

3. The Sun"s diameter is around 10 times that of Earth. (Hint)

4. observations of sunspots suggest that the sun rotates differentially. (Hint)

5. In the solar convection zone, the gas is partly ionized. (Hint)

6. Convection involves cool gas climbing toward the solar surface, and also hot gas sinking into the interior. (Hint)

7. most solar absorption lines are produced in the corona. (Hint)

8. There space as countless absorption lines in the solar spectrum as there are facets present in the Sun. (Hint)

9. The faintness that the chromosphere is a direct an outcome of its low temperature. (Hint)

10. The temperature that the solar corona reduce with enhancing radius. (Hint)

11. Sunspots are areas of extreme magnetic fields. (Hint)

12. Prominences are large flames erupting native the burning surface ar of the Sun. (Hint)

13. Positrons are the antiparticles of electrons. (Hint)

14. Nuclei are organized together through the solid force. (Hint)

15. Neutrinos are theoretical particles that are thought to exist but have never ever been detect experimentally. (Hint)


1. The part of the sun we actually watch is called the _____. (Hint)

2. Traveling exterior from the surface, the two main regions of the solar setting are the ____ and the _____. (Hint)

3. listed below the solar surface, in stimulate of increasing depth, lied the _____ zone, the _____ zone, and also the _____. (Hint)

4. _____ viewed on the surface of the sunlight is evidence of solar convection. (Hint)

5. The Sun shows up to have a well-defined edge because the thickness that the _____ is just 0.1 percent the the solar radius. (Hint)

6. The many abundant element in the sun is _____. (Hint)

7. The second most abundant facet in the sunlight is _____. (Hint)

8. The two most abundant aspects in the sunlight make up around _____ percent that its composition (by variety of atoms). (Hint)

9. The gas in the corona is extremely _____. (Hint)

10. Sunspots appear dark since they are _____ 보다 the bordering gas of the photosphere. (Hint)

11. The sunspot bike is _____ year long; the solar bike is _____ years long. (Hint)

12. The whole solar luminosity is created in the _____ (give the region) the the Sun. (Hint)

13. The net result of the proton—proton chain is the _____ protons space fused into a nucleus of _____ , two _____ space emitted, and energy is released in the type of _____. (Hint)

14. energy is released in the proton—proton chain because mass is _____ in the process. (Hint)

15. The solar neutrino difficulty is the fact that astronomers observe as well _____ neutrinos coming from the Sun. (Hint)


1. Name and briefly describe the main regions of the Sun. (Hint)

2. How enormous is the Sun, compared with Earth? (Hint)

3. How warm is the solar surface? The solar core? (Hint)

4. how do researchers construct models the the Sun? (Hint)

5. What is helioseismology, and what does it tell us about the Sun? (Hint)

6. describe how power generated in ~ the sun reaches Earth. (Hint)

7. Why go the Sun appear to have actually a sharp edge? (Hint)

8. offer the history of "coronium," and also tell just how it enhanced our understanding of the Sun. (Hint)

9. What is the solar wind? (Hint)

10. What is the cause of sunspots, flares, and also prominences? (Hint)

11. What fuel the Sun"s enormous energy output? (Hint)

12. What are the ingredients and the end result of the proton—proton chain in the Sun? Why is energy released in the process? (Hint)

13. Why are researchers trying so hard to detect solar neutrinos? (Hint)

14. describe some feasible solutions come the solar neutrino problem. (Hint)

15. What would we watch on earth if the Sun"s interior energy resource suddenly shut off? exactly how long perform you think it might take—minutes, days, years, countless years—for the Sun"s light to begin to fade? Repeat the inquiry for solar neutrinos. (Hint)


1. use the reasoning presented in ar 16.1 to calculation the value of the "solar constant" ~ above Jupiter. (Hint)

2. usage Wien"s regulation (Section 3.4) to identify the wavelength matching to the peak of the blackbody curve (a) in the core of the Sun, where the temperature is 107 K, (b) in the solar convection ar (105 K), and (c) just below the solar photosphere (104 K). What form (visible, infrared, ray, etc.) go the radiation take it in each case? (Hint)

3. The largest-amplitude solar sound waves have periods of around 5 minutes. This is the moment taken because that the waves to cross from one side of the sun to the other and back. Calculation the median speed that the wave. Compare the wave period with the orbital period of things moving just above the solar photosphere. (Hint)

4. If convected solar material moves at 1 km/s, just how long walk it take to flow throughout the 1000-km expanse that a typical granule? compare this with the around 10-minute lifetimes observed for many solar granules. (Hint)

5. usage Stefan"s legislation (flux

T4, where T is the temperature in kelvins; see ar 3.4) come calculate just how much less energy (as a fraction) is emitted every unit area the a 4500-K sunspot than from the neighboring 5800-K photosphere. (Hint)

6. The Sun"s differential rotation is responsible because that wrapping the solar magnetic field about the sunlight (Figure 16.19). Making use of the data presented in the sunlight Data table, calculate exactly how long it takes for material at the solar equator come "lap" the material near the poles—that is, to finish one extra trip roughly the Sun"s rotation axis.

7. how long does that take for the sun to transform one planet mass the hydrogen into helium? (Hint)

8. Assuming continuous luminosity, calculate how long it would certainly take the sunlight to radiate its very own mass right into space. (Hint)

9. The solar wind dead mass away from the sunlight at a price of about 900,000 kg/s. Compare this rate with the rate at which the sun loses fixed in the form of radiation. (Hint)

10. The whole reaction sequence shown in number 16.26 generates 4.3 10-12 joules that electromagnetic energy and releases two neutrinos. Assume that neutrino oscillations transform half of this neutrinos into other corpuscle by the moment they travel 1 A.U. Native the Sun. Estimate the total number of solar neutrinos passing through earth each second. (Hint)


The projects offered here all require a unique solar filter. Together filters are easily purchased from assorted sources.


1. An as necessary filtered telescope will certainly easily present you sunspots. Count the variety of sunspots you view on the Sun"s surface. Notification that sunspots frequently come in pairs or groups. Come earlier and look at again a couple of days later and also you"ll watch that the Sun"s rotation has actually caused spots come move, and also the point out themselves have actually changed. If a sufficiently huge sunspot (or, much more likely, sunspot group) is seen, continue to watch it together the sun rotates. It will certainly be out of watch for around 2 weeks. Can you identify the rotation of the sunlight from these observations?


See more: Which Of The Following Statements About Iso 9000 Is True? Chapter 18 Flashcards

Solar granulation is no too difficult to see. The environment of planet is most stable in the morning hours. Watch the sun on a cool morning, 1 or 2 hours after it has actually risen. Usage high magnification and look originally at the center of the Sun"s disk. Have the right to you see changes in the granulation pattern? They room there, however are not always obvious or basic to see.

3. view some solar prominences and also flares. Hydrogen-alpha filters space commercially available for small telescopes. Castle are rather expensive, however many science departments will have actually one. Girlfriend can regularly see prominences and flares even throughout times of sunspot minimum. You space actually city hall the chromosphere rather than the photosphere, therefore the sun looks quite various from its regular appearence.