Astronomy Chapter 8 HW

Part B: Twice Earth's distance from the Sun. Express your answer in watts per meter squared to two significant figures

1/4 * 1300 = 325 watts per square meter (watts/m^2)

Part C: 7 times Earth's distance from the Sun. Express your answer in watts per meter squared to two significant figures.

1/49 *1300 = 26.5 or 27 watts per square meter (watts/m^2)

Part A: About what is Rigel's surface temperature?

10,000 K

Part B: Rigel's luminosity is about _____ times the Sun's luminosity.

100,000

Part C: Rigel's radius is about _____ times the Sun's radius.

80

Part D: Given that our solar system is now about 4.6 billion years old, in which time will the Sun run out of hydrogen for fusion? Express your answer in years to two significant figures.

9.6-4.6 = 5.0*10^9 years

Part B: Five stars are shown on the following H-R diagrams. Rank the stars based on their surface temperature from highest to lowest. If two (or more) stars have the same surface temperature, drag one star on top of the other(s).

All five stars appear at the same place along the horizontal axis showing spectral type. Because spectral type is related to surface temperature, all five stars must have the same surface temperature.

Part E: Five stars are shown on the following H-R diagrams. Rank the stars based on their luminosity from highest to lowest; notice that these are the same five stars shown in Part D. If two (or more) stars have the same luminosity, drag one star on top of the other(s).

All five stars have the same luminosity because they are all at the same height along the vertical (luminosity) axis.

Part D: What type of visible light spectrum does the Sun produce? a continuous spectrum an emission line spectrum an absorption line spectrum

An absorption line spectrum The Sun can simplistically be pictured as a hot interior light source surrounded by a thin, cooler layer of gas (the Sun's photosphere). The interior produces a continuous spectrum, while the overlying gas acts like a cloud to produce absorption lines.

Part G: Five stars are shown on the following H-R diagrams; notice that these are the same five stars shown in Part F. Rank the stars based on their luminosity from highest to lowest. If two (or more) stars have the same luminosity, drag one star on top of the other(s).

As always, the H-R diagram shows surface temperature along the horizontal axis and luminosity along the vertical axis.

Part C: Most continuous spectra are examples of what we also call thermal radiation spectra. Why do we call them "thermal" spectra? Because thermal comes from a Greek root meaning "continuous." Because the peak wavelength of the spectrum depends on the temperature of the object producing the spectrum. Because these spectra have shapes that resemble those of traditional thermometers. Because these spectra can be produced only by very hot objects with temperatures of thousands of degrees or more.

Because the peak wavelength of the spectrum depends on the temperature of the object producing the spectrum.

Part B: Most interstellar clouds are made mostly of hydrogen (because hydrogen is the most common element in the universe). Why are these clouds usually dominated by the color red? Because red light passes more easily through space than other colors of light. Because the strongest visible emission lines from hydrogen are red. Because hydrogen gas clouds produce a continuous, red spectrum. Because hydrogen emits only red light, and no light of other colors.

Because the strongest visible emission lines from hydrogen are red.

Part B: Listed following is the same set of fictitious stars given in Part A. Rank the stars based on how bright each would appear in the sky as seen from Jupiter, from brightest to dimmest.

Brightest : Nismo 100LSun, 8 ly > Shelby 100LSun, 10 ly AND Ferdinand 400LSun, 20 ly > Enzo 200LSun, 20ly > Lotus 400LSun, 40 ly Dimmest Stars are so far away that any difference in distance to the stars from Earth and Jupiter is negligible. As a result, the answer to this part is the same as the answe

Part A: Listed following are several fictitious stars with their luminosities given in terms of the Sun's luminosity (LSun) and their distances from Earth given in light-years (ly). Rank the stars based on how bright each would appear in the sky as seen from Earth, from brightest to dimmest. If two (or more) stars have the same brightness in the sky, show this equality by dragging one star on top of the other(s).

Brightest : Nismo 100LSun, 8 ly > Shelby 100LSun, 10 ly AND Ferdinand 400LSun, 20 ly > Enzo 200LSun, 20ly > Lotus 400LSun, 40 ly Dimmest To be sure you understand the concept, notice the following facts: (1) Nismo is clearly brighter in the sky than Shelby, because it has the same luminosity but is nearer to us. (2) Enzo is twice as luminous and twice as far as Shelby; the inverse square law for light tells us that doubling distance makes an object four times as dim, so Enzo must be dimmer than Shelby. (3) Similarly, because Lotus has twice the luminosity and twice the distance of Enzo, it must be dimmer than Enzo. (4) Ferdinand has four times the luminosity and twice the distance of Shelby, so the inverse square law for light tells us that they are equally bright in our sky.

Part F: Which of the following layers of the Sun can be seen with some type of telescope? Consider all forms of light, but do not consider neutrinos or other particles. chromosphere radiation zone photosphere corona convection zone core

Chromosphere, photosphere, and Corona

Part E: Suppose we want to know what the Sun is made of. What should we do?

Compare the wavelengths of lines in the Sun's spectrum to the wavelengths of lines produced by chemical elements in the laboratory. Each chemical element (or ion or molecule) produces a unique set of spectral lines; the wavelengths of these lines can be measured in the laboratory. If the Sun's spectrum contains the set of lines for some particular element, we conclude that the Sun contains that element. We determine the Sun's overall chemical composition by examining all the lines in its spectrum.

Part A: First, launch the video below. Then, close the video window and answer the questions that follow. You can watch the video again at any point. Sort each item into the appropriate bin based on which type of spectrum it represents. Drag each item into one of the bins below.

Continuous Spectrum: A graph of this spectrum shows a smooth curve. The only one of the spectra below that does not give us information about chemical composition. Arises from relatively dense objects like light bulb, and people. Emission Line Spectrum: A graph of this spectrum has upward spikes. Produced by thin or low-density clouds of gas. Absorption Line Spectrum: Produced when starlight passes through thin or low-density clouds of gas. A graph of this spectrum shows a curve with sharp, downward dips.

Part E: In which of the following layer(s) of the Sun does nuclear fusion occur? chromosphere radiation zone photosphere corona convection zone core

Core

Part A: Following are the different layers of the Sun's atmosphere. Rank them based on the order in which a probe would encounter them when traveling from Earth to the Sun's surface, from first encountered to last

Corona > Chromosphere > Photosphere

Part C: Rank the layers of the Sun's atmosphere based on their temperature, from highest to lowest.

Corona > Chromosphere > Photosphere

Part D: Rank the layers of the atmosphere based on the energy of the photons that are typically emitted there, from highest to lowest.

Corona > Chromosphere > Photosphere

Part C: The following figure shows how four identical stars appear in the night sky seen from Earth. The shading is used to indicate how bright (white) or dim (dark gray) the star would appear in the sky from Earth. Rank the stars based on their distance from Earth, from farthest to closest.

Farthest: Dark Gray, Gray, Light Gray, White : Closest For stars of the same luminosity, apparent brightness decreases with distance (following the inverse square law for light). Therefore, the star that appears dimmest must be the most distant and the star that appears brightest must be the nearest. Remember that this is true ONLY if you know that all stars have the same intrinsic luminosity. Because there is no way to know luminosity just by looking at a star in the sky, you cannot in general use brightness to say anything about distance.

Part A: Listed following are the different layers of the Sun. Rank these layers based on their distance from the Sun's center, from greatest to least

Greatest Distance: Corona > Chromosphere > Photosphere > Convection Zone > Radiation Zone > Core :Least Distance

Part B: Rank the layers of the Sun based on their density, from highest to lowest.

Highest: Core > Radiation Zone > Convection Zone > Photosphere > Chromosphere > Corona :Least

Part D: Rank the following layers of the Sun based on the pressure within them, from highest to lowest.

Highest: Core > Radiation Zone > Convective Zone > Photosphere :Lowest

Part C: Rank the following layers of the Sun based on their temperature, from highest to lowest.

Highest: Core > Radiation Zone > Convective zone > Photosphere :Lowest

Part A: Consider the four stars shown following. Rank the stars based on their surface temperature from highest to lowest.

Highest: a blue white dwarf star > Sun > an orange main-sequence star > a red supergiant star :Lowest

Part A: The Sun's mass is about 2×1030kg; this mass was about 70% hydrogen when the Sun formed, with about 13% of this hydrogen ever becomes available for eventual fusion in the core. Use the given data calculate the total mass of hydrogen available for fusion over the lifetime of the Sun. Express your answer to two significant figures and include the appropriate units.

Hydrogen = 70% of MSun and available hydrogen is 13% of this Hydrogen = 70/100 * 2 * (10^30) = 1.40 * 10^30 kg Available hydrogen for fusion = (13/100) * 1.40 * 10^30 = 1.82 * 10^29 kg

A Time magazine cover once suggested that an "angry Sun" was becoming more active as human activity changed Earth's climate. It's certainly possible for the Sun to become more active at the same time that humans are affecting Earth, but is it possible that the Sun could be responding to human activity? Why or why not? It is impossible. Human activities can affect processes in the outer layers of the Sun, photosphere and corona, but the Sun's activity is regulated by the solar thermostat in the core. It is possible. Human activities cannot affect processes in the interior of the Sun, but can affect the outer layers of the Sun, photosphere and corona, which determine activity of the Sun. It is impossible. The sheer size of the Sun and the 150 million kilometer distance from Earth to the Sun make any human activity totally negligible compared to the processes inside it. It is possible. Human activities affect the whole Solar System, including the interior of the Sun through different radiations.

It is impossible. The sheer size of the Sun and the 150 million kilometer distance from Earth to the Sun make any human activity totally negligible compared to the processes inside it.

Part C: Five stars are shown on the following H-R diagrams; notice that these are the same five stars shown in Part B. Rank the stars based on their luminosity from highest to lowest. If two (or more) stars have the same luminosity, drag one star on top of the other(s).

Luminosity is shown along the vertical axis, with stars higher up more luminous than those lower down.

Part D: Based on its location on the HR diagram, what can we say about Rigel's mass and lifetime?

Nothing, because it is not on the main sequence.

Part A: Which of the following procedures would allow you to make a spectrum of the Sun similar to the one shown, though with less detail?

Pass a narrow beam of sunlight through a prism. The prism bends different wavelengths of light by different amounts, causing the white light from the Sun to spread out into a rainbow of colors. Absorption features appear as dark lines against the brighter background of the spectrum.

Part B: Rank the layers of the Sun's atmosphere based on their density, from highest to lowest.

Photosphere > Chromosphere > Corona

Listed following is a set of statements describing individual stars or characteristics of stars. Match these to the appropriate object category.

Red Giant or Supergiant Starts: Very cool but very luminous Found in the uppper right of the H-R diagram Main-sequence stars: The majority of stars in our galaxy The Sun, for example A very hot and very luminous star White dwarfs: not much larger in radius than Earth Very hot but very dim

Listed following are events or phenomena that occur during either the part of the sunspot cycle known as solar minimum or the part known as solar maximum. Match these items to the correct part of the sunspot cycle.

Solar Maximum: Occurs about 11 years after a solar maximum (on average) Solar flares are most common Auroras are most likely in Earth's skies Sunspots are most numerous on the Sun Orbiting satellites are most at risk Solar Minimum: Occurs about 5 to 6 years after a solar maximum (on average)

Part D: Five stars are shown on the following H-R diagrams. Rank the stars based on their surface temperature from highest to lowest. If two (or more) stars have the same surface temperature, drag one star on top of the other(s).

Spectral type is related to surface temperature, with stars of spectral type O having the highest surface temperature and stars of spectral type M having the lowest surface temperature. In other words, spectral type increases to the left on the H-R diagram.

Part F: Five stars are shown on the following H-R diagrams. Rank the stars based on their surface temperature from highest to lowest. If two (or more) stars have the same surface temperature, drag one star on top of the other(s).

Spectral type is related to surface temperature, with stars of spectral type O having the highest surface temperature and stars of spectral type M having the lowest surface temperature. In other words, spectral type increases to the left on the H-R diagram.

Part A: Earth is about 150 million kilometers from the Sun, and the apparent brightness of the Sun in our sky is about 1300 watts/m2. Using these two facts and the inverse square law for light, determine the apparent brightness that we would measure for the Sun if we were located at the following positions. Half Earth's distance from the Sun. Express your answer in watts per meter squared to two significant figures.

The Sun would appear four times brighter. So the apparent brightness would be 4 × 1,300 watts per square meter = 5,200 watts per square meter (watts/m^2)

Part C: Which of the following best describes why the Sun's spectrum contains black lines over an underlying rainbow?

The Sun's hot interior produces a continuous rainbow of color, but cooler gas at the surface absorbs light at particular wavelengths.

Part B: The Sun fuses about 600 billion kilograms of hydrogen each second. Based on your result from the previous part, calculate how long the Sun's initial supply of hydrogen can last. Express your answer in seconds to two significant figures.

Total lifetime of sun = 1.82 * 10^29 kg / 600 * 10^9 = 3.0 * 10^17 s

Part C: Give your answer from the previous part in years. Express your answer in years to two significant figures.

Total lifetime of sun in years = 3.0 * 10^17 / (365 * 24 * 60 * 60) = 9.6 * 10^9 years

Part F: Any spectrum can be displayed either in photographic form as shown to the left or as a graph. Which of the following graphs could represent a portion of the Sun's visible light spectrum?

Upward Curve with Dips The smooth part of the curve represents the graph of the background rainbow of color; the dips in the curve represent the black lines where light is missing from the rainbow.

Part A: Study the graph of the intensity of light versus wavelength for continuous spectra, observing how it changes with the temperature of the light bulb. Recall that one of the laws of thermal radiation states that a higher-temperature object emits photons with higher average energy (Wien's law). This law is illustrated by the fact that for a higher temperature object, the graph peaks at __________. a higher intensity a shorter wavelength a longer wavelength

Wien's law states that the thermal radiation from a hotter object peaks at a shorter wavelength

Part D: For an object producing a thermal spectrum, a higher temperature causes the spectrum to have ___________. more prominent emission lines more prominent absorption lines a peak intensity located at longer wavelength a peak intensity located at shorter wavelength

a peak intensity located at shorter wavelength

Part C: The absorption line spectrum shows what we see when we look at a hot light source (such as a star or light bulb) directly behind a cooler cloud of gas. Suppose instead that we are looking at the gas cloud but the light source is off to the side instead of directly behind it. In that case, the spectrum would __________. appear as a continuous rainbow of colors appear completely dark still be an absorption spectrum be an emission line spectrum

be an emission line spectrum Because the cloud absorbs light from the hot source, conservation of energy demands that it must re-emit light with the same total amount of energy. However, this re-emitted light is sent in all directions, not just along the direction from which it originally came. Therefore, if we view the cloud from a location from which we can see only the light that the cloud itself emits, we will see an emission line spectrum.

Part B: Compared to a high-luminosity main-sequence star, stars in the upper right of the H-R diagram are __________. hotter and larger in radius cooler and larger in radius cooler and smaller in radius hotter and smaller in radius

cooler and larger in radius

Part C: Compared to a low-luminosity main-sequence star, stars in the lower left of the H-R diagram are __________. hotter and larger in radius cooler and larger in radius cooler and smaller in radius hotter and smaller in radius

hotter and smaller in radius

Part A: View the video below: The H-R Diagram. Then answer the graded follow-up questions on the right. You can watch the video again at any point. Compared to a main-sequence star with a short lifetime, a main-sequence star with a long lifetime is __________. more luminous, hotter, larger, and more massive more luminous, hotter, smaller, and less massive less luminous, cooler, larger, and more massive less luminous, cooler, smaller, and less massive

less luminous, cooler, smaller, and less massive

Part B: In the illustration of the solar spectrum, the upper left portion of the spectrum shows the __________ visible light.

lowest frequency Red light is the longest wavelength visible light, and longer wavelength means lower frequency (because wavelength×frequency=speed of light).

Part B: Click "show" for the emission line spectrum, then click "choose gases" and study the emission line spectrum for neon. The neon "OPEN" sign appears reddish-orange because __________. neon atoms emit many more yellow and red photons than blue and violet photons neon atoms emit only yellow and red photons the yellow and red photons emitted by neon travel much faster than the blue and violet photons and so reach our eyes first each yellow and red photon emitted by neon carries more energy than each blue and violet photon emitted.

neon atoms emit many more yellow and red photons than blue and violet photons. The many more lines in the yellow and red parts of the spectrum are what make "pure" neon lights look red or orange. (When you see "neon lights" glowing with other colors (besides reddish-orange), it is generally because they contain additional elements (besides neon) making them glow.)

Part D: Notice that the Sun's spectrum appears brightest (or most intense) in the yellow-green region. This fact tells us __________.

the approximate temperature of the Sun's surface One of the two laws of thermal radiation (Wien's law) states that the peak wavelength of a spectrum is directly related to an object's temperature. A peak at yellow-green wavelengths corresponds to a temperature of about 5800 K.