Chapter 5.4-5.6

trap, arches, outbursts

1 Magnetic phenomena in the chromosphere and corona, like magnetic weather, result as constantly changing magnetic fields in the Sun's atmosphere ______ ionized gas to produce beautiful ______ and powerful ________. Some of this solar activity can affect Earth's magnetic field and atmosphere. This ultraviolet image of the solar surface was made by the NASA TRACE spacecraft. It shows hot gas trapped in magnetic arches extending above active regions. At visual wavelengths, you would see sunspot groups in these active regions.

sunspots, cooler, fourth, dark, full moon

1 The dark spots that appear on the Sun are only the visible traces of complex regions of activity. Evidence gathered over many years and at a wide range of wavelengths shows that __________ are clearly linked to the Sun's magnetic field. Spectra show that sunspots are _______ than the photosphere with a temperature of about 4200 K. The photosphere has an average temperature of about 5800 K. Because, according to the Stefan-Boltzmann law, the total amount of energy radiated by a surface depends on its temperature raised to the ________ power, sunspots look _____ in comparison with the photosphere. Actually, a sunspot emits quite a bit of radiation. If the Sun were removed and only an average-size sunspot were left behind, it would be brighter than a _____ ________.

continuous spectrum, absorption, cool, dark, dark-line, emission, excited, bright-line

1 To understand how to analyze a spectrum, begin with a simple incandescent lightbulb. The hot filament emits blackbody radiation, which forms a ______________ ______________. An _____________ spectrum results when radiation passes through a _______ gas. In this case you can imagine that the lightbulb is surrounded by a cool cloud of gas. Atoms in the gas absorb photons of certain wavelengths that are then missing from the observed spectrum, and you see ________ absorption lines at those wavelengths. Such absorption spectra are also called ________-_________ spectra. An _____________ spectrum is produced by photons emitted by an excited gas. You could see emission lines by turning your telescope aside so that photons from the bright bulb do not enter the telescope and the excited gas has a dark background. The photons you would see would be those emitted by the __________ atoms near the bulb, and the observed spectrum is mostly dark with a few bright emission lines. Such spectra are also called _________-__________ spectra

prominence, lower

1a A _________ is composed of ionized gas trapped in a magnetic arch rising up through the photosphere and chromosphere into the lower corona. Seen during total solar eclipses at the edge of the solar disk, prominences look pink because of emission in the three hydrogen Balmer lines, H-alpha, H-beta, and H-gamma. The image above shows the arch shape suggestive of magnetic fields. Seen from below against the Sun's bright surface, prominences form dark filaments. 1b Quiescent prominences may hang in the ______ corona for many days, whereas eruptive prominences burst upward in hours. The eruptive prominence below is many Earth diameters in length.

absorption, all, low-density, specific, cool

1a The spectrum of a star is an _______________ spectrum. The denser layers of the photosphere emit blackbody radiation. Gases in the atmosphere of the star absorb their specific wavelengths and form dark absorption lines in the spectrum. 1b In 1859, long before scientists understood atoms and electron energy levels, the German scientist Gustav Kirchhoff formulated three rules—now known as Kirchhoff's laws—describing the three types of spectra. KIRCHHOFF'S LAWS Law I: The Continuous Spectrum A solid, liquid, or dense gas excited to emit light will radiate at ____ wavelengths and thus produce a continuous spectrum. Law II: The Emission Spectrum A ______-____________ gas excited to emit light will do so at ____________ wavelengths and thus produce an emission spectrum. Law III: The Absorption Spectrum If light comprising a continuous spectrum passes through a _________, low-density gas, the result will be an absorption spectrum.

transition, inward, emission, outward, absorption

2 Electron orbits in the hydrogen atom are shown here as energy levels. When an electron makes a ______________ from one orbit to another, this means that the energy stored in the atom has changed. In this diagram, arrows pointed ___________ toward the nucleus represent transitions that result in the ______________ of a photon. If the arrows pointed ______________, they would represent transitions that result from the ______________ of a photon. Long arrows represent large amounts of energy and correspondingly short-wavelength photons.

reconnection events, distort

2 Solar flares rise to maximum in minutes and decay in an hour. They occur in active regions where oppositely directed magnetic fields meet and cancel each other in what are called ____________ ________. Energy stored in the magnetic fields is released as short-wavelength photons plus high-energy protons and electrons. X-ray and ultraviolet photons reach Earth in 8 minutes and increase ionization in our upper atmosphere, which can interfere with radio communications. Particles from flares reach Earth hours or days later as gusts in the solar wind, which can ______ Earth's magnetic field and disrupt navigation systems. Solar flares can also cause surges in electrical power lines and damage to Earth satellites. 2a Below, waves rush outward at 50 km/s from the site of a solar flare 40,000 times stronger than the 1906 San Francisco earthquake. The biggest solar flares can be a billion times more powerful than a hydrogen bomb.

number, 11 years, high, equator, maunder butterfly diagram

2 The _________ of spots visible on the Sun varies in a cycle with a period of __ _______. At maximum, there are often more than 100 spots visible. At minimum, there are very few or zero. 2a Early in a cycle, spots appear at _____ latitudes north and south of the Sun's equator. Later in the cycle, new spots appear closer to the Sun's _______. If you plot the latitude of sunspots versus time, the graph looks like butterfly wings, as shown in this ________ _________ ________, named after E. Walter Maunder of Greenwich Observatory.

Greek letters

2a Transitions in the hydrogen atom can be grouped into series—the Lyman series, Balmer series, Paschen series, and so on, named after scientists who carefully investigated the spectra of hydrogen atoms. Transitions and the resulting spectral lines are identified by ___________ ___________. Only the first few transitions in the first three series are shown below.

infrared, ultraviolet, balmer, ionized

2b In this drawing of the hydrogen spectrum, emission lines in the _____________ and _____________ are shown as gray. Only the first three lines of the Balmer series are visible to human eyes. 2c Excited clouds of gas in space emit light at all of the ___________ wavelengths, but you see only the red, blue, and violet photons blending to create the purple-pink color typical of ____________ hydrogen.

electrical currents, photons, disturbances

2b The solar wind, enhanced by eruptions on the Sun, interacts with Earth's magnetic field and can create _________ _________ with up to a million megawatts of power. Those currents flowing down into a ring around Earth's magnetic poles excite atoms in Earth's upper atmosphere to emit ______, as shown below. The emission results in glowing clouds and curtains of auroras 2c Reconnection events can release enough energy to blow large amounts of ionized gas outward from the corona in coronal mass ejections (CMEs). If a CME strikes Earth, it can produce especially violent _________ in Earth's magnetic field.

zeeman effect, photons, multiple, strength, reduced, less, cooler, hotter

3 Astronomers can measure magnetic fields on the Sun using the ________ ________, as shown below. When an atom is in a magnetic field, the electron energy levels are altered, and the atom is able to absorb ______ with a greater variety of wavelengths than the same atom not in a magnetic field. In this spectrum you see single spectral lines split into ________ components, with the separation between the components proportional to the _________ of the magnetic field. 3a Images of the Sun below show that sunspots contain magnetic fields a few thousand times stronger than Earth's. Such strong fields inhibit motions of ionized gas below the photosphere; consequently, convection is ______ below the sunspot, ____ energy is transported from the interior, and the Sun's surface at the position of the spot is ______. Heat that is prevented from emerging at the sunspot's position is deflected and emerges around the sunspot, making the surrounding area _______ than the average photosphere. The deflected heat can be detected in ultraviolet and infrared images; the result is that the entire active region, including the sunspots, is actually emitting more energy than the same area of normal photosphere.

dips

3 Modern astronomers rarely work with spectra in the form of images of bands of light. Spectra are usually recorded digitally, so it is easy to represent them as graphs of intensity versus wavelength. Here, the artwork above the graph suggests the appearance of a stellar spectrum. The graph at right reveals details not otherwise visible and allows comparison of relative intensities. Notice that dark absorption lines in the spectrum appear as ________ in the intensity graph.

coronal holes, away

3 Much of the solar wind comes from ________ ______, where the magnetic field does not loop back into the Sun. These open magnetic fields allow ionized gas in the corona to flow _____ as the solar wind. The dark area in this X-ray image at right is a coronal hole.

maunder minimum, spacecraft

4 Historical records show that there were very few sunspots from about 1645 to 1715, a phenomenon known as the ________ ________. This coincides with the middle of a period called the "Little Ice Age," a time of unusually cool weather in Europe and North America from about 1500 to about 1850, as shown in the graph below. Other such periods of cooler climate are known. Evidence suggests that there is a link between solar activity and the amount of solar energy Earth receives. This link has been confirmed by measurements made by _________ above Earth's atmosphere.

active, more

5 Observations at nonvisual wavelengths reveal that the chromosphere and corona above sunspots are violently disturbed in what astronomers call _______ regions. Spectrographic observations show that active regions contain powerful magnetic fields. If all wavelengths are included, Earth receives ______ radiation from the spotted, active Sun than at times of low activity. Arched structures above an active region are evidence of gas trapped in magnetic fields. (complexity of an active region becomes visible at short wavelengths )

negative, coulomb, electrons, energy, energy, tightly, large, farther, less, quanta

5-4a Electron Shells The electrons are bound to the atom by the attraction between their ___________ charge and the positive charge on the nucleus. This attraction is known as the _____________ force. A positive ion is an atom with missing ___________, meaning fewer electrons than protons. For an atom to go through the ionization process, there needs to be a certain amount of _________ to pull an electron completely away from the nucleus. This energy is the electron's binding energy, the energy that holds it to the atom. The size of an electron's orbit is related to the _________ that binds it to the atom. If an electron orbits close to the nucleus, it is _________ bound, and a _________ amount of energy is needed to pull it away. Consequently, its binding energy is large. An electron orbiting __________ from the nucleus is held more loosely, and _____ energy is needed to pull it away. That means it has less binding energy. Nature permits atoms only certain amounts (_________) of binding energy, and the laws that describe how atoms behave are called the laws of quantum mechanics. The properties of atoms, blackbody radiation, and the interactions of light and matter are based on the laws of quantum mechanics

specific, energy levels, lowest, distance, more, difference, excited, released, collision

5-4b The Excitation of Atoms Each orbit in an atom represents a _________ amount of binding energy, so physicists commonly refer to the orbits as _________ _________. Using this terminology, you can say that an electron in its smallest and most tightly bound orbit is in its _________ permitted energy level. You could move the electron from one energy level to another by supplying enough energy to make up the difference between the two energy levels. It would be like moving a flowerpot from a low shelf to a high shelf: The greater the ______________ between the shelves, the ________ energy you would need to raise the pot. The amount of energy needed to move the electron is the energy __________ between the two energy levels. If you move the electron from a lower energy level to a higher energy level, you can call the atom an __________ atom. That is, you have added energy to the atom by moving its electron. If the electron falls back to the lower energy level, that energy is _____________. An atom can become excited by __________. If two atoms collide, one or both may have electrons knocked into higher energy levels. This happens very commonly in hot gas, where the atoms move rapidly and collide often.

wavelength, electromagnetic radiation, long, short

5-4c Measuring Velocities: The Doppler Effect The Doppler effect is an apparent change in the ____________ of radiation caused by relative motion of a source and observer. Astronomers use it to measure the speed of blobs of gas in the Sun's atmosphere toward or away from Earth, as well as speeds of entire stars and galaxies. When astronomers talk about the Doppler effect, they are talking about small shifts in the wavelength of _________________ ___________. The Doppler effect, however, can occur for waves of all types—sound waves, for example. You probably hear the Doppler effect in sound every day without realizing what it is. The pitch of a sound is determined by its wavelength. Sounds with ________ wavelengths have low pitches, and sounds with ________ wavelengths have higher pitches. You hear the Doppler effect every time a car or truck passes you and the pitch of its engine noise or emergency siren seems to drop. Its sound is shifted to shorter wavelengths and higher pitches while it is approaching, and is shifted to longer wavelengths and lower pitches after it passes by, as shown in Figure 5-7a. The Doppler effect. (a) The sound waves (black circles) emitted from a siren on an approaching truck will be received more often, and thus be heard with a higher pitch, than the sound waves from a stationary truck. The siren will have a lower pitch if it is going away from the observer. (b) A moving source of light emits waves that move outward (black circles). An observer toward whom the light source is moving observes a shorter wavelength (a blueshift); an observer for whom the light source is moving away observes a longer wavelength (a redshift).

temperature, composition, motion

5-5 THE SUN'S ATMOSPHERE Topic 5-6 Science is a way of understanding nature, and the spectrum of the Sun tells you a great deal about such things as the Sun's _____________ and the _____________ and ___________ of the gases in the solar photosphere and atmosphere. In later chapters you will use spectra to study stars, galaxies, and planets, but you can begin with spectra of the Sun.

photospheres, matter, absorbed, emitted, energy levels, balmer

5-5a Formation of Spectra Spectra of the Sun and other stars are formed as light passes from their ________________ outward through their atmospheres. Look over Concept Art 5A, "Atomic Spectra." Notice the following three important properties of spectra: 1) There are three kinds of spectra described by three simple rules. When you see one of these types of spectra, you can recognize the arrangement of __________ that emitted the light. Dark (absorption) lines in the Sun's spectrum are caused by atoms in the Sun's (or Earth's) atmosphere between you and the Sun's photosphere. The photosphere itself produces a blackbody (continuous) spectrum. 2) The wavelengths of the photons that are ____________ by a given type of atom are the same as the wavelengths of the photons __________ by that type of atom; both are determined by the electron ___________ ____________ in the atom. The emitted photons coming from a hot cloud of hydrogen gas have the same wavelengths as the photons absorbed by hydrogen atoms in the Sun's atmosphere. Although the hydrogen atom produces many spectral lines, called the ___________ lines, from the ultraviolet to the infrared, only three hydrogen lines, called the Balmer lines, are visible to human eyes. 3) Most modern astronomy books display spectra as graphs of intensity versus wavelength. Be sure you see the connection between dark absorption lines, bright emission lines, and dips and peaks in the graphed spectrum.

elements, helium, absent, hydrogen, cool, visible

5-5b The Sun's Chemical Composition Identifying the ______________ in the Sun's atmosphere by identifying the lines in its spectrum is a relatively straightforward procedure. For example, two dark absorption lines appear in the yellow region of the solar spectrum at the wavelengths 589.0 nm and 589.6 nm. The only atom that can produce this pair of lines is sodium, so the Sun must contain sodium. More than 90 elements in the Sun have been identified this way. The element __________ was known in the Sun's spectrum first, before helium (from the Greek word helios, meaning "Sun") was found on Earth. However, just because spectral lines that are characteristic of an element are missing, you cannot conclude that the element itself is ________. For example, the hydrogen Balmer lines are weak in the Sun's spectrum, yet more than 90 percent of the atoms in the Sun are _____________. The reason for this apparent paradox is that the Sun is too _______ to produce strong hydrogen Balmer lines. At the Sun's photosphere temperature, atoms do not usually collide violently enough to knock electrons in hydrogen atoms into the second energy level, which is the necessary starting place for Balmer line absorptions. Spectral lines of other varieties of atoms (e.g., ionized calcium) are especially easy to observe in the Sun's spectrum because the Sun is the right temperature to excite those atoms to the energy levels that can produce __________ spectral lines, even though those atoms are not very common in the Sun.

chromosphere, corona, total solar eclipse, pink

5-5c The Chromosphere Above the photosphere lies the ______________. Solar astronomers define the lower edge of the chromosphere as lying just above the visible surface of the Sun with its upper regions blending gradually with the atmosphere's outermost layer, the ___________. You can think of the chromosphere as being an irregular layer with an average depth less than Earth's diameter, as seen in Figure 5-8a. Because the chromosphere is roughly 1000 times fainter than the photosphere, you can see it with your unaided eyes only during a ________ _______ ___________ when the Moon covers the brilliant photosphere. Then, the chromosphere flashes into view as a thin line of pink just above the photosphere. The word chromosphere comes from the Greek word chroma, meaning "color." The _______ color is produced by combined light of three bright emission lines—the red, blue, and violet Balmer lines of hydrogen. ((a) A cross-section at the edge of the Sun shows the relative thickness of the photosphere and chromosphere. Earth is shown for scale. On this scale, the disk of the Sun would be more than 1.5 m (5 ft) in diameter. The corona extends from the top of the chromosphere to great height above the photosphere. (b) This photograph, made during a total solar eclipse, shows only the inner part of the corona.)

corona, sunspots

5-5d The Corona The outermost part of the Sun's atmosphere is called the _______, after the Greek word for "crown." The corona is so dim that it is not visible in Earth's daytime sky because of the glare of scattered light from the Sun's brilliant photosphere. During a total solar eclipse, however, when the Moon covers the photosphere, you can see the innermost parts of the corona, as shown in Figure 5-8b. Observations made with specialized telescopes called coronagraph on Earth or in space can block the light of the photosphere and record the corona out beyond 20 solar radii, almost 10 percent of the way to Earth. Such images reveal that _________ are linked with features in the chromosphere and corona (Figure 5-11). (Coronagraph images reveal the corona by blocking light from the much brighter solar disk. The activity cycles and magnetic fields that play an important role in the photosphere and the chromosphere also affect the corona.)

magnetic fields

5-6 SOLAR ACTIVITY Topic 5-CR The Sun is not quiet. It is home to slowly changing spots larger than Earth and rapid, vast eruptions that dwarf human imagination. All of these seemingly different forms of solar activity have one thing in common—__________ ________.

screen, galileo, sphere, rotating

5-6a Observing the Sun Solar activity is often visible with even a small telescope, but you should be very careful about observing the Sun. It is not safe to look directly at the Sun, and it is even more dangerous to look at the Sun through any optical instrument such as a telescope, binoculars, or even the viewfinder of a camera. These concentrate sunlight and can cause severe injury. You can safely project an image of the Sun onto a ________, or you can use specially designed solar blocking filters. In the early 17th century, _______ observed the Sun and saw spots on its surface; day by day, he saw the spots moving across the Sun's disk. He correctly concluded that the Sun is a ________ and is ________. (These sketches of the location and structure of sunspots on successive days show evidence of solar rotation as well as gradual changes in the size and structure of sunspots, as Galileo found in 1610)

magnetic fields, number, locations, strength, climate, layers

5-6b Sunspots The dark sunspots that you see at visible wavelengths only hint at the complex processes that go on in the Sun's atmosphere. To explore those processes, you must turn to the analysis of images and spectra at a wide range of wavelengths. Study Concept Art 5B, "Sunspots and the Solar Magnetic Cycle," and notice the following five important points: 1) Sunspots are cool spots on the Sun's surface caused by strong _______ ________. 2) Sunspots follow an 11-year cycle not only in the _________ of spots visible but also in their ___________ on the Sun. 3) The Zeeman effect gives astronomers a way to measure the ________ of magnetic fields on the Sun. 4) Characteristics of the sunspot cycle vary over centuries and appear to affect Earth's _________. 5) Finally, there is clear evidence that sunspots are part of a larger magnetic process that involves other ________ of the Sun's atmosphere and parts of its interior in a 22-year cycle.

cyclical, equatorial, magnetic

5-6d The Sun's Magnetic Cycle Sunspots are magnetic phenomena, so the 11-year cycle of sunspots must be caused by ________ changes in the Sun's magnetic field. To explore that idea, you can begin with the Sun's rotation. The Sun does not rotate as a rigid body. It is a gas from its outermost layers down to its center, and some parts of the Sun rotate faster than other parts. Figure 5-14a demonstrates how the __________ region of the photosphere rotates faster than do regions at higher latitudes. At the equator, the photosphere rotates once every 24.5 days, but at latitude 45° one rotation takes 27.8 days. Helioseismology can map the rotation throughout the interior (Figure 5-14b). This phenomenon is called differential rotation, and it is clearly linked with the ________ cycle. ((a) In general, the photosphere of the Sun rotates faster at the equator than at higher latitudes. If you started five sunspots in a row, they would not stay lined up as the Sun rotates. (b) Detailed analyses of the Sun's interior rotation from helioseismology reveal regions of slow rotation (blue) and rapid rotation (red). Such studies show that differential rotation occurs inside the Sun as well as on its surface.)

babcock model, conductor, must, frozen, sunspots pairs

5-6e The Babcock Model for Solar Activity The Sun's magnetic cycle is not fully understood, but the _________ _________ explains the magnetic cycle as a progressive tangling and then untangling of the solar magnetic field (Figure 5-16). Because the electrons in an ionized gas are free to move, the gas is a very good ________ of electricity, and any magnetic field in the gas is "frozen" (firmly embedded) in the gas. If the gas moves, the magnetic field _____ move with it. The Sun's magnetic field is ______ into its gases, and the differential rotation wraps this field around the Sun like a long string caught in a rotating wheel. Rising and sinking gas currents twist the field into ropelike tubes, which tend to float upward. Where these magnetic tubes burst through the Sun's surface, ________ ______ occur. (The Babcock model of the solar magnetic cycle explains the sunspot cycle as a primary consequence of the Sun's differential rotation gradually winding up and tangling the magnetic field near the base of the Sun's outer, convective layer.)

magnetic, weak, ionized, prominences, filaments, eruptions, solar wind

5-6f Chromospheric and Coronal Activity The solar magnetic fields extend high into the chromosphere and corona, where they produce beautiful and powerful phenomena. Study Concept Art 5C, "Solar Activity and the Sun-Earth Connection," and notice the following three important points: 1) All solar activity is _________. You do not experience such events on Earth because Earth's magnetic field is _____ and Earth's atmosphere is not _________, so it is free to move independent of the magnetic field. On the Sun, however, the "weather" is a magnetic phenomenon. 2) Tremendous energy can be stored in arches of magnetic fields. These are visible near the edge of the solar disk as _________, and, seen from above, as _________. When that stored energy is released, it can trigger powerful ___________; and, although these eruptions occur far from Earth, they can affect Earth in dramatic ways, including auroral displays. Aurorae, the eerie and pretty northern and southern lights, are produced when gases in Earth's upper atmosphere glow from energy delivered by the solar wind. 3) In some regions of the solar surface, the magnetic field does not loop back. High-energy gas from these regions flows outward and produces much of the ______ _______.

photon, passes, wavelength, higher, right

Another way an atom can get the energy that moves an electron to a higher energy level is to absorb a _________ (packet) of electromagnetic radiation. Only a photon with exactly the right amount of energy corresponding to the energy difference between the two levels can move the electron from one level to another. If the photon has too much or too little energy, the atom cannot absorb it, and the photon __________ right by. Because the energy of a photon depends on its ________________, only photons of certain wavelengths (certain colors) can be absorbed by a given kind of atom. Figure 5-5 shows the lowest four energy levels of the hydrogen atom, along with three photons the atom could absorb. The longest-wavelength (reddest) photon has only enough energy to excite the electron from the first to the second energy level, but the shorter-wavelength (higher-energy, bluer) photons can excite the electron to _______ levels. A photon with too much or too little energy cannot be absorbed. Because the hydrogen atom has many more energy levels than shown in Figure 5-5, it can absorb photons of many different wavelengths. A hydrogen atom can absorb only those photons that have exactly the _______ energy to move the atom's electron to one of the higher-energy orbits. In this drawing, three photons with different wavelengths are shown along with the changes they respectively would produce in the orbit of the electron starting from the lowest orbital if they were absorbed.

spectrum, emission, second

Astronomers know a great deal about the chromosphere from its _____________. The chromosphere produces an ___________ spectrum, and Kirchhoff's ___________ law tells you the chromosphere must be an excited, transparent, low-density gas viewed with a dark, cold background. The chromosphere's density relative to the density of the air you breathe on Earth's surface ranges from 1/10,000 just above the photosphere to 1/100 billion just below the corona.

ionized, lost, filtergram, high, structures

Atoms in the lower chromosphere are ___________, and atoms in the higher layers of the chromosphere are even more highly ionized—that is, they have ______ more electrons. From this, astronomers can find the temperature in different parts of the chromosphere. Just above the photosphere, the temperature falls to a minimum of about 4500 K and then rises to the extremely high temperatures of the corona. Solar astronomers can take advantage of some of the physics of spectral line formation to study the chromosphere. A photon with a wavelength corresponding to one of the solar atmosphere's strong absorption lines is very unlikely to escape from deeper layers and reach Earth. A ___________ is a photograph made using light in one of those dark absorption lines. Those photons can only come from ________ in the solar atmosphere. In this way, filtergrams reveal detail in the upper layers of the chromosphere. In a similar way, an image recorded in the far-ultraviolet or in the X-ray part of the spectrum reveals other ____________ in the hottest parts of the solar atmosphere (Simultaneous images of the solar photosphere and chromosphere. The ultraviolet image primarily shows material in the upper chromosphere that is much hotter than the photosphere. This pair of images shows that low-temperature sunspots have extra-hot active regions above them in the chromosphere.)

unstable, lower, ground state, tightly, photon, quantum jumps, motion, electromagnetic radiation, amount,

Atoms, like humans, cannot exist in an excited state forever. The excited atom is _________ and must eventually (usually within 10-9 to 10-6 seconds) give up the energy it has absorbed and return its electron to a ____________ energy level. The lowest energy level an electron can occupy is called the ________________ ___________. When the electron drops from a higher to a lower energy level, it moves from a loosely bound level to one that is more __________ bound. The atom then has a surplus of energy—the energy difference between the levels—that it can emit as a _________. Study the sequence of events in Figure 5-6 to see how an atom can absorb and emit photons. Jumps of electrons from one orbit to another are sometimes called ______________ ____________. In casual language that term has come to mean a huge change, but now you see that it in fact represents a very small change. The quantum jump represents a change of electron _______, so _______________ ___________ is either released or absorbed in the process. An atom can absorb a photon only if the photon has the correct ________ of energy. The excited atom is unstable and within a fraction of a second returns to a lower energy level, reradiating the photon in a random direction.

binding, permitted orbits, between, nucleus, differs, electrons, masses

Because atoms can only have certain amounts of _____________ energy, your model atom can have orbits of only certain sizes, called _____________ _______. These are like steps in a staircase: You can stand on the number-one step or the number-two step but not on the number-one-and-one-quarter step. The electron can occupy any permitted orbit but not orbits in _____________. The arrangement of permitted orbits depends primarily on the charge of the _________, which in turn depends on the number of protons. The number of protons in the nucleus is unique to each element. Consequently, as shown in Figure 5-4 for hydrogen, helium, and boron, each kind of element has its own pattern of permitted orbits. Ionized forms of an element have orbital patterns quite different from their un-ionized forms. The arrangement of permitted orbits ______ for every kind of atom and ion. Isotopes of an element have almost—but not quite—the same pattern of permitted electron orbits as each other because they have the same number of ____________ while their nuclei have slightly different _________. An electron in an atom may occupy only certain permitted orbits. Because each element has a different number of protons and therefore a different electrical charge in the nucleus attracting the electrons, each element has a different, unique pattern of permitted orbits. >Hydrogen nuclei have just one positive charge, so the electron orbits are not pulled close to the nucleus >Helium nuclei have two positive charges, Only the innermost electron orbits are shown in these three examples. >Boron nuclei have five positive charges, so the electron orbits are tightly bound to the nucleus.

wavelengths, energy levels

Because each type of atom or ion has its unique set of energy levels, each type absorbs and emits photons with a unique set of ____________. As a result, you can identify the elements in a gas by studying the characteristic wavelengths of light absorbed or emitted. It is important to note that the wavelengths (colors) emitted and absorbed by jumping electrons are determined not by the starting or ending energy level of the jump, but by the difference between the ______________ ___________. The process of excitation and emission is a common sight in urban areas at night. A neon sign glows when atoms of neon gas in the glass tube are excited by electricity flowing through the tube. As the electrons in the electric current flow through the gas, they collide with the neon atoms and excite them. As you have seen, immediately after an atom is excited, its electron drops back to a lower energy level, emitting the surplus energy as a photon of a certain wavelength. The visible photons emitted by the most common electron jumps within excited neon atoms produce a reddish-orange glow. Street signs of other colors, erroneously also called "neon," contain other gases or mixtures of gases instead of pure neon.

filaments, spicules, cooler, hotter

Figure 5-10a shows a filtergram made at the wavelength of Hα, the hydrogen Balmer-alpha line. This image shows complex structure in the chromosphere, including long, dark ________ silhouetted against the brighter surface. __________ are flamelike jets of gas extending upward into the chromosphere and lasting 5 to 15 minutes. Figure 5-10b shows how, at the limb of the Sun's disk, the spicules blend together and look like flames covering a burning prairie, but they are not flames at all. Spectra show that spicules are _______ gas from the lower chromosphere extending upward into hotter regions. Spectroscopic analysis of the chromosphere shows that it is a low-density gas in constant motion where the temperature increases rapidly with height. Just above the chromosphere lies even ________ gas. (This hydrogen Balmer-alpha filtergram reveals complex structures in the chromosphere including long, dark filaments. (b) Seen at the edge of the solar disk, spicules look like a burning prairie, but they are not at all related to burning. The white circle shows the size of Earth to Scale)

confirm, confirming, consolidation

HOW DO WE KNOW? CONFIRMATION AND CONSOLIDATION What do scientists do all day? The scientific method is sometimes portrayed as a kind of assembly line where scientists crank out new hypotheses and then test them through observation. In reality, scientists don't often generate entirely new hypotheses. It is rare that an astronomer makes an observation that disproves a long-held theory and triggers a revolution in science. Then what is the daily grind of science really about? Many observations and experiments __________ already-tested hypotheses. The biologist knows that all worker bees in a hive are sisters because they are all female, and they all had the same mother, the queen bee. A biologist can study the DNA from many workers and confirm that hypothesis. By repeatedly ____________ a hypothesis, scientists build confidence in the hypothesis and may be able to extend it. Do all of the workers in a hive have the same father, or did the queen mate with more than one male drone? Another aspect of routine science is _________, the linking of a hypothesis to other well-studied phenomena. A biologist can study yellow jacket wasps from a single nest and discover that the wasps, too, are sisters. There must be a queen wasp who lays all of the eggs in a nest. But in a few nests, the scientist may find two sets of unrelated sister workers. Those nests must contain two queens sharing the nest for convenience and protection. From a study of wasps, the biologist consolidates what is known about bees with what others have learned about wasps and reveals something new: that bees and wasps have evolved in similar ways for similar reasons. Confirmation and consolidation allow scientists to build confidence in their understanding and extend it to explain more about nature.

behave, location, motion, orbits

HOW DO WE KNOW? QUANTUM MECHANICS How can you understand nature if it depends on the atomic world you cannot see? You can see objects such as stars, planets, aircraft carriers, and hummingbirds, but you can't see individual atoms. As scientists apply the principle of cause and effect, they study the natural effects they can see and work backward to find the causes. Invariably that quest for causes leads back to the invisible world of atoms. Quantum mechanics is the set of rules that describe how atoms and subatomic particles __________. On the atomic scale, particles behave in ways that seem unfamiliar. One of the principles of quantum mechanics specifies that you cannot know simultaneously the exact _________ and _________ of a particle. This is why physicists prefer to go one step beyond the simple atomic model that imagines electrons as particles following _________, and instead describe the electrons in an atom as if they each were a cloud of negative charge. That's a better model. This raises some serious questions about reality. Is an electron really a particle at all? If you can't know simultaneously the position and motion of a specific particle, how can you know how it will react to a collision with a photon or another particle? The answer is that you can't know, and that seems to violate the principle of cause and effect. Many of the phenomena you can see depend on the behavior of huge numbers of atoms, and quantum mechanical uncertainties average out. Nevertheless, the ultimate causes that scientists seek lie at the level of atoms, and modern physicists are trying to understand the nature of the particles that make up atoms. This is one of the most exciting frontiers of science.

distant, vary, magnetic

If the Sun is truly a representative star, you might expect to find similar magnetic cycles on other stars, but they are too ______ for spots to be directly visible. Some stars, however, _____ in brightness over a period of days, in a way revealing that they are marked with dark spots believed to resemble sunspots. Other stars have features in their spectra that vary over periods of years, suggesting that they are subject to ________ cycles much like the Sun's cycle. Once again, the evidence tells you that the Sun is a normal star.

electrons

LIGHT, MATTER, AND MOTION Topic 5-5 If light did not interact with matter, you would not be able to see these words. In fact, you would not exist, because, among other problems, photosynthesis would be impossible, and there would be no grass, wheat, bread, beef, cheeseburgers, or any other kind of food. The interaction of light and matter makes your life possible, and it also makes it possible for you to understand the Universe. You should begin your study of light and matter by considering __________ that are within atoms. As you learned in the previous chapter, electrons and other charged particles produce light when they change speed or direction of their motion.

emission spectrum (bright-line spectra)

Law 2:____________________ _______________- A spectrum produced by photons emitted by an excited gas.

absorption spectrum (dark-line spectrum)

Law 3: ____________________ _______________- A spectrum that contains absorption lines.

continuous spectrum

Law I: _________________ _______________- A spectrum in which there are no absorption or emission lines.

space, solar wind, extension, rapidly,

Not all of the Sun's magnetic field loops back toward the Sun; some of the field lines lead outward into ______. Gas from the solar atmosphere follows along the magnetic fields that point outward and flows away from the Sun in a breeze called the _______ _______ that can be considered an _________ of the corona. The low-density gases of the solar wind blow past Earth at 300 to 800 km/s with gusts as high as 1000 km/s (more than 2 million mph). Because of the solar wind, the Sun is slowly losing mass, but this is a minor loss for an object as massive as the Sun. The Sun loses about 1 million tons per second, but that is only 10^-14 of the solar mass per year. Later in life, the Sun, like many other stars, will lose mass _______. Do other stars have chromospheres, coronae, and stellar winds like the Sun? Ultraviolet and X-ray observations suggest that the answer is yes. The spectra of many stars contain emission lines in the far-ultraviolet that could only have formed in the low-density, high-temperature gases of a chromosphere or corona. Also, many stars are sources of X-rays that appear to have been produced by the high temperature gas in coronae. This observational evidence gives astronomers good reason to believe that the Sun, for all its complexity, is a typical star.

radial velocity

Note that the Doppler shift is sensitive only to the part of the velocity directed away from you or toward you, called the _________ __________ (Vr). A star moving perpendicular to your line of sight, to the left for instance, would have no blueshift or redshift because its distance from Earth would not be decreasing or increasing. Police radar guns use the Doppler effect to measure the speeds of cars. The police park next to the highway and aim their "hair dryers" directly along the road because they can measure only radial velocities, and they want to measure your full velocity along the highway.

forced, align, rotation, reversed, upward, latitude, delayed

The Babcock model also explains the reversal of the Sun's magnetic field from cycle to cycle. As the magnetic field becomes tangled, adjacent regions of the Sun's surface are dominated by magnetic fields that point in different directions. After about 11 years of tangling, the field becomes so complex that adjacent regions of the surface are _______ to change their magnetic field directions to _____ with neighboring regions. The entire field quickly rearranges itself into a simpler pattern, and differential ________ begins winding it up to start a new cycle. The newly organized field is _______, and the next sunspot cycle begins with magnetic north replaced by magnetic south. Consequently, the complete magnetic cycle is 22 years long, whereas the sunspot cycle is 11 years long. This magnetic cycle seems to explain the Maunder butterfly diagram (look back to Concept Art 5B, "Sunspots and the Sunspot Cycle"). As a sunspot cycle begins, the twisted tubes of magnetic force first begin to float ______ and produce sunspot pairs at higher _______. In other words, the first sunspots in a new cycle appear far from the Sun's equator. Later in the cycle the field is more tightly wound, and tubes of magnetic force arch through the surface at lower latitudes, so sunspot pairs appear closer to the equator. Notice the power of scientific models. Even though models of the sky and of atoms are only partly correct, they serve as organizing themes to guide further investigation. Similarly, the Babcock model is incomplete. For example, the solar cycle that should have begun around mid-2008 was _________ to late 2009. The subsequent 2013 cycle maximum was the weakest in 100 years in number of sunspots and amount of solar magnetic activity. The Babcock model does not easily account for such behavior. Nevertheless, the model provides a framework for organizing investigations of complex solar activity (How Do We Know?).

outward, ionized, convection, dynamo effect, pairs, magnet

The Sun's magnetic field appears to be powered by the energy flowing _______ in the form of moving currents of gas. The gas is highly _________, so it is a very good conductor of electricity. When an electrical conductor rotates rapidly and is stirred by ________, it can convert some of the energy flowing outward as convection into a magnetic field. This process is called the ________ _______, and it is believed to operate also in the liquid metal of Earth's core to produce Earth's magnetic field. Helioseismology observations have found evidence that the Sun's magnetic field is generated by the dynamo effect at the bottom of the convection zone deep under the photosphere. The Sun's magnetic cycle is clearly related to how its magnetic field is created. The magnetic behavior of sunspots provides an insight into how the magnetic cycle works. Sunspots tend to occur in groups or _____, and the magnetic field around the pair resembles that around a bar _________ with one end magnetic north and the other end magnetic south. At any one time, sunspot pairs south of the Sun's equator have reversed polarity compared to those north of the Sun's equator. Figure 5-15 illustrates this by showing sunspot pairs south of the Sun's equator with magnetic south poles leading and sunspots north of the Sun's equator with magnetic north poles leading. At the end of an 11-year sunspot cycle, the new spots appear with reversed magnetic polarity. (In sunspot groups, here simplified into pairs of major spots, the leading spot and the trailing spot have opposite magnetic polarity. Spot pairs in the Southern Hemisphere have reversed polarity from those in the Northern Hemisphere.)

sunspot, below, helioseismology, vibrations, temperature, density, rotation

The __________ groups are merely the visible traces of magnetically active regions. But what causes this magnetic activity? The answer appears to be linked to the cyclical strengthening and weakening of the Sun's overall magnetic field. 5-6c Insight into the Sun's Interior Almost no light emerges from _______ the photosphere, so you can't see into the solar interior. However, solar astronomers can use the vibrations in the Sun to explore its depths in a type of analysis called ___________. Random motions in the Sun constantly produce vibrations. Astronomers can detect these __________ by observing Doppler shifts in the solar surface. These waves make the photosphere move up and down by small amounts— roughly plus or minus 15 km (10 mi). This covers the surface of the Sun with a pattern of rising and falling regions that can be mapped, as shown in Figure 5-13. In the Sun, a vibration with a period of 5 minutes is strongest, but other periods are observed ranging from 3 to 20 minutes. Just as geologists can study Earth's interior by analyzing vibrations from earthquakes, solar astronomers can use helioseismology to map the ___________, _______, and rate of ________ in the Sun's invisible interior. (Model of one possible solar vibration mode, for comparison with helioseismology data. The Sun can vibrate in millions of different patterns or modes, and each mode corresponds to a different vibration wavelength that penetrates to a different level in the solar interior. By measuring Doppler shifts produced as the photosphere moves gently up and down, astronomers can map the inside of the Sun)

stars, similar, hydrogen, helium,

The effect of temperature on the visibility of spectral lines was first understood by Cecila Payne (later, Payne-Gaposchkin), who was an astronomer doing Ph.D. research work at Harvard Observatory in the 1920s. She used the new techniques of quantum mechanics to derive accurate chemical abundances for the Sun and other stars and so was the first person to know that the Sun is mostly composed of hydrogen, even though its visible-wavelength hydrogen spectral lines are only moderately strong. Astronomers must use the physics that describe the interaction of light and matter to analyze a star's spectrum, taking into account the star's temperature, to calculate correctly the amounts of each element present in the star. Such results show that nearly all ________ have compositions ________ to the Sun—about 90 percent of the atoms are ____________, and about 9 percent are ________, with small traces of heavier elements (Table 5-1). It is fair to say that Cecilia Payne, whose thesis has been called the most important doctoral work in the history of astronomy, figured out the true chemical composition of the Universe.

continuous spectrum, highly, altitudes, rises, low, magnetic fields, resist, heats

The spectrum of the corona can tell you a great deal about the coronal gases and simultaneously illustrate how astronomers analyze a spectrum. Some of the light from the corona produces a _________ __________ that lacks absorption lines. Superimposed on the corona's continuous spectrum are emission lines of _______ ionized gases. In the lower corona, the atoms are not as highly ionized as they are at higher _______, and this tells you that the temperature of the corona _____ with altitude. Just above the chromosphere, the coronal temperature is about 500,000 K, but in the outer corona the temperature can be 2,000,000 K or more. Despite that very high temperature, the corona does not produce much light because its density is very _____, only 10^4‍atoms/cm^3 or less. That is about 50 trillion times less dense than Earth's sea-level atmosphere. Astronomers have wondered for years how the corona and chromosphere can be so hot. Heat flows from hot regions to cool regions, never from cool to hot. So how can the heat from the photosphere, with a temperature of only 5800 K, flow out into the much hotter chromosphere and corona? Observations made by the SOHO satellite show a magnetic carpet of looped _________ _____ extending up through the photosphere. Remember that the gas of the chromosphere and corona has a very low density, so it can't ______ movement in the magnetic fields. Turbulence below the photosphere seems to flick the magnetic loops back and forth and whip the gas about. That ______ the gas. In this instance, energy appears to flow outward in the form of agitation of the magnetic fields.

shorter, bluer, blueshift, away, longer, redder, redshift, direction, spectral lines, motion, change, speed, size

Understanding the Doppler effect for sound lets you understand the similar Doppler effect for light. Imagine a light source emitting waves continuously as it approaches you. The light will appear to have a __________ wavelength, making it slightly ______. This is called a __________. A light source moving _______ from you has a __________ wavelength and is slightly __________. This is a _________. Redshifted and blueshifted spectra produced by a moving light source are illustrated in Figure 5-7b. The terms redshift and blueshift are used to refer to any range of wavelengths. The light does not actually have to be red or blue, and the terms apply equally to wavelengths in the radio, X-ray, or gamma-ray parts of the spectrum. "Red" and "blue" refer to the relative __________ of the shift, not to actual color. Also, note that these shifts are much too small to noticeably change the color of a star, but they are easily detected by changes in the positions of narrow features in a star's spectrum such as _____________ ___________ (discussed in detail in the next section). The Doppler shift, blue or red, reveals the relative _________ of wave source and observer—you measure the same Doppler shift if the light source is moving and you are stationary, or if the light source is stationary and you are moving, as you can see in Figure 5-7b. The amount of ___________ in wavelength depends on the ___________ of the source. A moving car has a smaller sound Doppler shift than a jet plane, and a slow-moving star has a smaller light Doppler shift than one that is moving at high velocity. You can measure the speed of a star toward or away from you by measuring the _____ of the Doppler shift of its spectral lines.

ion

______- An atom that has lost or gained one or more electrons.

active region

_______ _______- A magnetic region on the solar surface that includes sunspots, prominences, flares, and the like.

magnetic polarity

________ ________- Orientation and strength of a magnetic field's north and south poles.

flare

________- A violent eruption on the Sun's surface. .

coronal mass ejection (CMEs)

_________ ____ _________- Matter ejected from the Sun's corona in powerful surges guided by magnetic fields.

coronal holes

_________ _____- An area of the solar surface that is dark at X-ray wavelengths, thought to be associated with divergent magnetic fields and the source of the solar wind.

filaments

_________- A solar eruption, seen from above, silhouetted against the bright photosphere.

aurora

_________- The glowing light display that results when a planet's magnetic field guides charged particles toward the north and south magnetic poles, where they strike the upper atmosphere and excite atoms to emit photons.

maunder minimum

__________ _________- A period between 1645 and 1715 of less numerous sunspots and other solar activity.

dynamo effect

__________ _________- The process by which a rotating, convecting body of conducting matter, such as in Earth's core or in the Sun's convection zone, can generate a magnetic field.

radial velocity (Vr)

__________ ____________- That component of an object's velocity directed away from or toward the observer.

Babcock model

___________ _______- A model of the Sun's magnetic cycle in which the differential rotation of the Sun winds up and tangles the solar magnetic field. This is thought to be responsible for the sunspot cycle.

zeeman effect

___________ ________- The splitting of spectral lines into multiple components when the atoms are in a magnetic field.

excited atom

___________ _________- An atom in which an electron has moved from a lower to a higher energy level.

corona

___________- The faint outer atmosphere of the Sun, composed of low-density, high-temperature gas.

convection zone

____________ _______- A region inside a star where energy is carried outward as rising hot gas and sinking cool gas.

maunder butterfly diagram

____________ __________ __________- A graph showing the latitude of sunspots versus time, first plotted by W. W. Maunder in 1904.

energy levels

____________ __________- One of a number of states an electron may occupy in an atom, depending on its binding energy.

differential rotation

____________ ___________- The rotation of a body in which different parts of the body have different periods of rotation. This is true of the Sun, the giant planets like Jupiter, and the disk of the galaxy.

solar wind

____________ ____________- Rapidly moving atoms and ions that escape from the solar corona and blow outward through the Solar System.

redshift

____________- A Doppler shift toward longer wavelengths caused by a velocity of recession.

blueshift

____________- A Doppler shift toward shorter wavelengths caused by a velocity of approach.

prominence

____________- Eruption on the solar surface. Visible during total solar eclipses.

reconnection event

_____________ _______- On the Sun, the merging of magnetic fields to release energy in the form of flares.

doppler effect

_____________ _________- The change in the wavelength of radiation due to relative radial motion of source and observer.

balmer series

_____________ __________- A series of spectral lines produced by hydrogen in the near-ultraviolet and visible parts of the spectrum. The three longest-wavelength Balmer lines are visible to the human eye.

paschen series

_____________ __________- Spectral lines in the infrared spectrum of hydrogen produced by transitions whose lowest energy level is the third.

lyman series

_____________ __________- Spectral lines in the ultraviolet spectrum of hydrogen produced by transitions whose lowest energy level is the ground state.

binding energy

_____________ __________-The energy needed to pull an electron away from its atom.

ionization

_____________- The process in which atoms lose or gain electrons.

quantum mechanics

______________ ___________- The study of the behavior of atoms and atomic particles.

permitted orbits

______________ ____________- One of the unique orbits that an electron may occupy in an atom. one of the energy levels in an atom that an electron may occupy

transition

______________- The movement of an electron from one atomic energy level to another.

quantum jumps

_______________ ________- Jumps of electrons from one orbit or energy state to another.

ground state

_______________ ________- The lowest permitted electron energy level in an atom.

magnetic carpet

_______________ ______________- The network of small magnetic loops that covers the solar surface.

filaments

_______________- A solar eruption, seen from above, silhouetted against the bright photosphere.

helioseismology

_______________- The study of the interior of the Sun by the analysis of its modes of vibration. (Vibrations caused by motion in Sun and analyzing them to map temperature, density, and rate of rotation in Sun's interior)

kirchhoff's laws

________________ _______- A set of laws that describe the absorption and emission of light by matter.

filtergram

________________- A photograph (usually of the Sun) taken in the light of a specific region of the spectrum—for example, an Hα (hydrogen Balmer-alpha) filtergram. A photograph of the sun at a particular frequency range

Coulomb force

_________________ _____________- The electrostatic force of repulsion or attraction between charged bodies.

emission lines

__________________ _______- An isolated bright or dark line in a spectrograph produced by emission or absorption of light of a single wavelength, generally corresponding to a specific shift in the energy of an electron moving from one orbital to another. (not in textbook)

Spicules

___________________- A small, flamelike projection in the chromosphere of the Sun.

absorption lines

____________________ ______- A dark line in a spectrum produced by the absence of photons absorbed by atoms or molecules.

continuous spectrum

____________________ _______________- A spectrum in which there are no absorption or emission lines.

chromosphere

______________________- Bright gases just above the photosphere of the Sun.