Astronomy Test 1 Test Questions – Flashcards
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Which of the following has your address in the correct order?
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You, Earth, solar system, Milky Way Galaxy, Local Group, Local Supercluster, universe
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Where is our solar system located within the Milky Way Galaxy?
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about two-thirds of the way from the center of the galaxy to the outskirts of the galactic disk near the far outskirts of the galactic disk
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about two-thirds of the way from the center of the galaxy to the outskirts of the galactic disk near the far outskirts of the galactic disk
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100 billion
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Suppose we imagine the Sun to be about the size of a grapefruit. How big an area would the orbits of the nine planets of the Solar System cover?
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the size of a typical campus
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What do we mean when we say that the universe is expanding?
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Average distances are increasing between galaxies.
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The age of the universe is
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between 10 billion and 16 billion years.
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The earth is made mostly of metals and rocks. Where did this material come from?
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It was produced by nuclear fusion in stars.
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Why does Carl Sagan say that we are star stuff?
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Nearly every atom from which we are made once (before the solar system formed) was inside of a star.
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Which of the following statements does not use the term light-year in an appropriate way
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It will take me light-years to complete this homework assignment.
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Suppose we look at a photograph of many galaxies. Assuming that all galaxies formed at about the same time, which galaxy in the picture is the youngest?
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the one that is farthest away
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Suppose we imagine the Sun to be about the size of a grapefruit. Which of the following describes the size and distance of the earth on the same scale?
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The earth is the size of a point about 15 meters away from the Sun.
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Which of the following is smallest?
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size of a typical planet
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Which of the following is largest?
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size of a typical galaxy
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Suppose we imagine the Sun to be about the size of a grapefruit. How far away are the nearest stars (the three stars of Alpha Centauri)?
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2,500 miles
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If we use 1 millimeter to represent 1 light-year, how large in diameter is the Milky Way Galaxy?
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100 meters
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Which of the following best describes the Milky Way Galaxy?
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a spiral galaxy with a disk about 100,000 light-years in diameter and containing between 100 billion and 1 trillion stars
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How long would it take to count all the stars in the Milky Way Galaxy at a rate of one star per second?
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several thousand years
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How many galaxies are there in the observable universe?
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roughly (within a factor of 10) the same as the number of stars in our galaxy
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If you represented each star by a grain of sand, how much sand would it take to represent all the stars in the universe?
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more than all the sand on all the beaches on Earth
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On the scale of the cosmic calendar, in which the history of the universe is compressed to 1 year, how long has human civilization (i.e., since ancient Egypt) existed?
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a few seconds
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On a cosmic calendar, in which the history of the universe is compressed into one year, how long is the average human life span?
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0.2 second
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Approximately how fast are you moving with the rotation of the earth?
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1,300 km/hr
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What is an astronomical unit?
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the average distance from the earth to the Sun
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Patterns of stars in constellations hardly change in appearance over times of even a few thousand years. Why?
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The stars in our sky actually move rapidly relative to us-thousands of kilometers per hour-but are so far away that it takes a long time for this motion to make a noticeable change in the patterns in the sky
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How long does it take our solar system to complete one orbit around the Milky Way Galaxy?
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230 million years
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Which of the following statements about the Milky Way Galaxy is not true?
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Our solar system is located very close to the center of the Milky Way Galaxy.
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Which of the following correctly lists speeds from slowest to fastest?
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Earth's speed of rotation on its axis, typical speeds of stars in the local solar neighborhood relative to us, Earth's speed of revolution about the Sun, the speed of our solar system orbiting the center of the Milky Way Galaxy, the speeds of very distant galaxies relative to us
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The distribution of the mass of the Milky Way Galaxy is determined by
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studying the rotation of the galaxy.
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From the fact that virtually every galaxy is moving away from us and more distant galaxies are moving away from us at a faster rate than closer ones, we conclude that
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the universe is expanding.
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By studying distant galaxies in the 1920s, Hubble made the following important discovery that led us to conclude that the universe is expanding:
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all galaxies outside the Local Group are moving away from us, and the farther away they are, the faster they're going.
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n Imagine that we put a raisin cake into the oven, with each raisin separated from the others by 1 cm. An hour later, we take it out and the distances between raisins are 3 cm. If you lived in one of the raisins and watched the other raisins as the cake expanded, which of the following would you conclude?
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More distant raisins would be moving away from you faster.
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Which scientists played a major role in overturning the ancient idea of an Earth-centered universe, and about when?
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Copernicus, Kepler, and Galileo; about 400 years ago
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The names of the seven days of the week are based on the
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seven naked-eye objects that appear to move among the constellations
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Suppose the planet Uranus were much brighter in the sky, so that it was as easily visible to the naked eye as Jupiter or Saturn. Which one of the following statements would most likely be true in that case?
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A week would have eight days instead of seven.
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What do the structures of Stonehenge, the Templo Mayor, the Sun Dagger, and the Big Horn Medicine Wheel all have in common?
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They were all used by ancient peoples for astronomical observations.
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At the Sun Dagger in New Mexico, a dagger-shaped beam of sunlight pierces a spiral
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at noon on the summer solstice.
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The Muslim fast of Ramadan occurs
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during the ninth month of a 12-month lunar cycle.
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he Jewish calendar is kept roughly synchronized with a solar calendar by
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adding a thirteenth lunar month to 7 out of every 19 years.
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Which ancient culture had the greatest known success in predicting eclipses?
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Mayans
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Ptolemy was important in the history of astronomy because he
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developed a model of the solar system that made sufficiently accurate predictions of planetary positions to remain in use for many centuries.
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When did Ptolemy live?
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about 2000 years ago
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How did the Ptolemaic model explain the apparent retrograde motion of the planets?
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It held that the planets moved along small circles that moved on larger circles around the earth.
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Where was the Sun in Ptolemy's model of the universe?
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between the orbits of Venus and Mars
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When Copernicus first created his Sun-centered model of the universe, it did not lead to substantially better predictions of planetary positions than the Ptolemaic model. Why not?
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Galileo's observations of the moons of Jupiter.
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Kepler's third law, p2 = a3 , means that
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all orbits with the same semimajor axis have the same period. the period of a planet does not depend on its mass. planets that are farther from the Sun move at slower average speeds than nearer planets. a planet's period does not depend on the eccentricity of its orbit. All are right!!
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From Kepler's third law, a hypothetical planet that is twice as far from the Sun as the earth should have a period of
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more than 2 Earth years.
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From Kepler's third law, an asteroid with an orbital period of 8 years lies at an average distance from the Sun equal to
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4 astronomical units.
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Question Kepler's second law, which states that as a planet moves around its orbit it sweeps out equal areas in equal times, means that
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a planet travels faster when it is nearer to the Sun and slower when it is farther from the Sun.
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All the following statements are true. Which one follows directly from Kepler's third law?
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Venus orbits the Sun at a slower average speed than Mercury.
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One of the "nails in the coffin" for the earth-centered universe was
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Galileo's observations of the moons of Jupiter
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When Copernicus first created his Sun-centered model of the universe, it did not lead to substantially better predictions of planetary positions than the Ptolemaic model. Why not?
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Copernicus used perfect circles for the orbits of the planets.
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The speed of light is 300,000 km/s. How far is a light-year? Be sure to show all work clearly on your calculation
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1 light-year = (speed of light) × (1 yr) = 300,000 km s × 1 yr × 365 days 1 yr × 24 hr 1 day × 60 min 1 hr × 60 s 1 min = 9,460,000,000,000 km
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Briefly explain what we mean by the statement ʺThe farther away we look in distance, the further back we look in time.ʺ
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It means that when we look at a distant object, we see it as it was some time in the past, rather than as it is now. This is because the light we see has taken time to travel from the object to us.
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Imagine that you could drive your car in space. Assume that you can drive at a constant speed of 100 kilometers per hour. Suppose you started driving from the Sun. How long would it take, in years, to reach Earth?
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t = 149.6 million km 100 km/hr = 1.5 million hours = 171 years
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Based on the idea of ʺspaceship Earth,ʺ write one or two paragraphs explaining why it is not the case that we are ʺjust sitting here.ʺ
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Far from just sitting still, we on the earth are moving relative to the Sun, planets, stars, and even other galaxies. The rotation of the earth causes the most noticeable changes in the sky. This motion around the earthʹs axis causes the Sun and stars to appear to rise and set, producing what we call a ʺday.ʺ The revolution of the earth about the Sun produces the monthly changes of the constellations, the seasonal weather changes due to the earthʹs tilt, and the parallax of some stars. The precession of the earthʹs axis, a very slow movement that has a period of 26,000 years, causes the movement of the North Star, and the changing position of the equinoxes and solstices. The motion of the Sun relative to the stars in the local solar neighborhood is at an extremely fast speed, although barely noticeable. Over time, this movement causes the patterns of the stars in the sky to change. The rotation of the galaxy means that the entire solar system is also orbiting the center of the Milky Way. This also produces motions of stars and clouds of gas. The expansion of the universe, the fact that the space between most galaxies is increasing with time, means that almost all galaxies outside the Local Group are moving away from us, with the more distant ones moving away faster. All of these motions, although not felt by us on Earth, are observed by watching the sky and prove that we are not ʺjust sitting here.ʺ
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) Discuss the scientific meanings of, and the relationships between, the following terms: law, hypothesis, theory. In this context, explain what is wrong with this statement: ʺThe Big Bang is just a theory; it is not yet a law because it has not yet been proven
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Laws are generally mathematical equations. They describe a relationship between different variables. There are laws to describe the relationship between the pressure, volume, and temperature of a gas. There are laws that describe the relationship between the mass of a body and the acceleration due to gravity caused by that body. There are laws explaining the likelihood of a person inheriting a recessive trait from their parentsʹ genetic code. On the other hand, a theory isnʹt an equation, and usually canʹt be expressed quite as elegantly. Theories are explanations of how things work. For instance, the theory of gravity explains what forces are acting to create gravity and keep us on the ground. Even if you tested this extensively, and it worked every time, it couldnʹt become a law -- laws describe relationships. Theories are the extensively tested ʺhowsʺ and ʺwhysʺ of those relationships. A hypothesis is a tentative explanation for an observed phenomenon. It must make (or lead to) a testable prediction. Theory does not mean guess, or hunch, or hypothesis. A theory does not change into a scientific law with the accumulation of new or better evidence. A theory will always be a theory, a law will always be a law. A theory will never become a law, and a law never was a theory. Laws are generalizations that describe phenomena, whereas theories explain phenomena. For example, the laws of thermodynamics describe what will happen under certain circumstances; thermodynamics theories explain why these events occur. Laws, like facts and theories, can change with better data. But theories do not develop into laws with the accumulation of evidence. Rather, theories are the goal of science. A theory is never ʺproven.ʺ But over time scientists develop more and more confidence in a theory if its predictions continue to be found true after extensive experimentation and evidence.
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Intelligent Design refers to the idea that a "designer" is responsible for the origin of the universe and of life in all its diversity. Explain why most scientists agree that Intelligent Design does not qualify as a scientific theory.
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6) Key points: testable predictions, falsifiability
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Which object has the most kinetic energy?
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a 2-ton truck moving 90 km/hr
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What does temperature measure?
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the average kinetic energy of particles in a substance
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Suppose you heat up an oven and boil a pot of water. Which of the following explains why you would be burned by sticking your hand briefly in the pot but not by sticking your hand briefly in the oven?
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The water has a higher heat content than the oven
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Considering Einstein's famous equation, E = mc2 , which of the following statements is true?
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A small amount of mass can be turned into a large amount of energy
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At extremely high temperatures (e.g., millions of degrees), which of the following best describes the phase of matter?
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a plasma consisting of positively charged ions and free electrons
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When an atom loses an electron, it becomes
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ionized.
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When an atom absorbs a photon containing energy, any of the following can happen except which?
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An electron moves from an upper energy level to a lower one.
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How can an electron in an atom lose energy to go from a higher energy level to a lower energy level?
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It releases a photon equal in energy to its own energy drop
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Which of the following is an example in which you are traveling at constant speed but not at constant velocity?
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driving around in a circle at exactly 100 km/hr
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As long as an object is not gaining or losing mass, a net force on the object will cause a change in
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acceleration
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If your mass is 60 kg on Earth, what would your mass be on the Moon?
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60kg
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The fact that Voyager 10 continues to speed out of the solar system, even though its rockets have no fuel, is an example of
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Newton's first law of motion.
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A skater can spin faster by pulling in her arms closer to her body or spin slower by spreading her arms out from her body. This is due to
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conservation of angular momentum
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According to the universal law of gravitation, if you triple the distance between two objects, then the gravitational force between them will
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decrease by a factor of 9.
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According to the universal law of gravitation, if you double the masses of both attracting objects, then the gravitational force between them will
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increase by a factor of 4.
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Grass (that is healthy) looks green because
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it reflects green light and absorbs other colors
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How are wavelength, frequency, and energy related for photons of light?
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Longer wavelength means lower frequency and lower energy.
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From shortest to longest wavelength, which of the following correctly orders the different categories of electromagnetic radiation?
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gamma rays, X rays, ultraviolet, visible light, infrared, radio
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Which of the following statements about X rays and radio waves is not true?
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X rays travel through space faster than radio waves. X rays have higher frequency than radio waves. X rays have higher energy than radio waves. X rays and radio waves are both forms of light, or electromagnetic radiation. X rays have shorter wavelengths than radio waves.
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When an electron in an atom goes from a higher energy state to a lower energy state, the atom
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emits a photon of a specific frequency.
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If two objects are the same size but one object is 3 times hotter than the other object, the hotter object emits
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81 times more energy.
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From laboratory measurements, we know that a particular spectral line formed by hydrogen appears at a wavelength of 486.1 nanometers (nm). The spectrum of a particular star shows the same hydrogen line appearing at a wavelength of 485.9 nm. What can we conclude?
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The star is moving toward us.
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You observe a distant galaxy. You find that a spectral line normally found in the visible part of the spectrum is shifted toward the infrared. What do you conclude?
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The galaxy is moving away from you.
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Suppose you see two stars: a blue star and a red star. Which of the following can you conclude about the two stars? Assume that no Doppler shifts are involved. (Hint: Think about the laws of thermal radiation.)
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The blue star has a hotter surface temperature than the red star
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Suppose you have a chunk of water ice. Describe what happens to it, in terms of phases, as you raise the temperature to millions of degrees
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The ice melts into liquid, then evaporates into gas. At higher temperatures, the water molecules dissociate atoms. At very high temperatures, the atoms are ionized.
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The most common isotope of uranium is U-238, but the form used in nuclear bombs and nuclear power plants is U-235. Given that uranium has atomic number 92, how many neutrons are in each of these two isotopes? [
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U-238 has 146 neutrons, and U-235 has 3 fewer, or 143 neutrons.
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An isotope of fluorine has 9 protons and 10 neutrons. What are the atomic number and atomic weight of this fluorine? If we added a proton to this fluorine nucleus, would the result still be fluorine? What if we added a neutron instead? Explain.
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The atomic number of fluorine is equal to the number of protons, 9. The atomic weight is equal to the number of protons plus neutrons, 19. If we added a proton, it would no longer be fluorine. If we added a neutron instead, it would just be another isotope of fluorine, with atomic number 9 but atomic weight 20
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p2 = 4π2 G M1 + M2 a3 4) Suppose a solar system has a star that is four times more massive than our Sun. If that solar system has a planet the same size as Earth, orbiting at a distance of 1 AU, what is the orbital period of the planet? Explain. [Hint: You donʹt need to use a calculator to answer this question.]
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From Keplerʹs law, we see that the period depends on the inverse square root of the object masses. Thus, if we have a star four times as massive as the Sun, the period of a planet orbiting at 1 AU will be half that of the earth, or 6 months.
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Briefly explain why spectral lines are useful in determining the chemical composition of their source
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Every chemical element has a unique set of atomic energy levels and therefore a unique set of spectral lines. Thus, by identifying spectral lines, we can identify the elements that produced them
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Briefly explain how we can use spectral lines to determine an objectʹs radial motion. Can we also learn the objectʹs tangential motion (across our line of sight) from its spectral lines?
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By comparing the wavelength of the spectral lines in the objectʹs spectrum to the rest wavelengths of the same lines, we measure the Doppler shift. This tells us the objectʹs radial motion: A shift toward shorter wavelength means the object is moving toward us, and a shift to longer wavelength means it is moving away from us. We cannot learn anything about the objectʹs tangential motion from its spectral lines because this does not affect the line positions
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graph
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Bead
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When did humans learn that the Earth is not the center of the universe?
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Within the past 500 years
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Suppose we make a scale model of our solar system, with the Sun the size of a grapefruit. Which of the following best describes what the planets would look like?
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Answer Selected Answer: They are all much smaller than the Sun. Four planets are within about 20 meters of the Sun, while the remaining planets are spread much farther apart, with Pluto more than a half a kilometer from the Sun.
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Which of the following has your "cosmic address" in the correct order?
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You, Earth, solar system, Milky Way Galaxy, Local Group, Local Supercluster, universe
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Astronomers infer that the universe is expanding because distant galaxies all appear to
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be moving away from us, with more distant ones moving faster
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Where is our solar system located within the Milky Way Galaxy?
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Roughly halfway between the center and the edge of the visible disk of the galaxy
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How do the speeds at which we are moving with the Earth's rotation and orbit compare to the speeds of more familiar objects?
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he Earth's rotation is carrying most people around the axis faster than a commercial jet travels, and the Earth's orbit is carrying us around the Sun faster than the Space Shuttle orbits the Earth.
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How long would it take to count all the stars in the Milky Way Galaxy at a rate of one star per second?
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Several thousand years
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Suppose we look at two distant galaxies: Galaxy 1 is twice as far away as Galaxy 2. In that case
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We are seeing Galaxy 1 as it looked at an earlier time in the history of the universe than Galaxy 2.
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When we look at an object that is 1,000 light-years away we see it
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as it was 1,000 years ago.
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Using the ideas discussed in the text, in what sense are we "star stuff"?
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Nearly every atom from which we are made was once inside of a star.
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If we imagine the history of the universe compressed into one year, the first dinosaurs walked on Earth
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about 6 days ago.
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The total number of stars in the observable universe is abou
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the same as the number of grains of sand on all the beaches on Earth
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Relative to the age of the universe, how old is our solar system
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is between about one-quarter to one-half the age of the universe
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How are galaxies important to our existence?
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Galaxies recycle material from one generation of stars to the next, and without this recycling we could not exist
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Why do the patterns of the stars in our sky look the same from year to year?
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Although these stars move quite fast by human standards, they are so far away that it would take thousands of years for their motion to be noticeable to the eye.
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Galileo challenged the idea that objects in the heavens were perfect by
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observing sunspots on the Sun and mountains on the Moon.
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Our standard hour is always the same amount of time (60 minutes, or 1/24 of a solar day). In contrast, the hour of ancient Egypt
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was longer than today's hour in the summer and shorter than today's hour in the winter.
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Earth is farthest from the Sun in July and closest to the Sun in January. During which northern hemisphere season is Earth moving fastest in its orbit?
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Winter
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How did the Ptolemaic model explain the apparent retrograde motion of the planets?
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It held that the planets moved along small circles that moved on larger circles around the Earth, and that the combined motion sometimes resulted in backward motion.
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Which of the following is NOT part of a good scientific theory?
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A scientific theory cannot be accepted until it has been proven true beyond all doubt.
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All the following statements are true. Which one follows directly from Kepler's third law (p2 = a3)?
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venus orbits the Sun at a slower average speed than Mercury.
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Suppose that the planet Uranus were much brighter in the sky, so that it was as easily visible to the naked eye as Jupiter or Saturn. Which one of the following statements would most likely be true in that case?
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A week would have 8 days instead of 7.
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What do the structures of Stonehenge, the Templo Mayor, the Sun Dagger, and the Big Horn Medicine Wheel all have in common
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They were all used by ancient peoples for astronomical observations.
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When Copernicus first created his Sun-centered model of the universe, it did not lead to substantially better predictions of planetary positions than the Ptolemaic model. Why not?
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Copernicus used perfect circles for the orbits of the planets.
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Ptolemy was important in the history of astronomy because he
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developed a model of the solar system that made sufficiently accurate predictions of planetary positions to remain in use for many centuries.
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Theastrology practiced by those who cast predictive horoscopes can be tested by __________ ____________________
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comparing how often the predictions come true to what would be expected by pure chance.
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Which of the following is NOT one of the major hallmarks of science?
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New scientific ideas are always based on small changes to old ideas and are never revolutionary.
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Which of the following represent the smallest range of temperature?
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0 to 100 degrees Fahrenheit
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When a rock is held above the ground, we say it has some potential energy. When we let it go, it falls and we say the potential energy is converted to kinetic energy. Finally, the rock hits the ground (and stays there). What has happened to the energy?
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The energy goes to producing sound and to heating the ground, rock and surrounding air
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An atom in an excited state contains more of what type of energy than the same atom in the ground state?
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electric potential energy
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An atom which has 4 protons and 6 neutrons will be electrically neutral if it contains
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4 electrons
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Suppose you built a scale-model atom in which the nucleus is the size of a tennis ball. About how far would the cloud of electrons extend?
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several kilometers
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Suppose you kick a soccer ball straight up to a height of 10 meters. Which of the following is true about the gravitational potential energy of the ball during its flight?
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he ball's gravitational potential energy is greatest at the instant when the ball is at its highest point.
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How much energy would be released if we could completely convert the mass of a 1 kilogram rock into energy?
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9 x 10^16 joules
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Suppose you had some molecular oxygen (O2) chilled enough so that it was in liquid form. Which of the following best describes the phase changes that would occur as you heated the liquid oxygen up?
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It would evaporate into a gas, then the molecules would dissociate into individual oxygen atoms, then the atoms would become increasingly ionized as you continued to raise the temperature.
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If an electron at level 1 in a hydrogen atom absorbs 10.2 eV of energy, it will move to level 2. What typically happens next?
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The electron returns to level 1 by releasing 10.2 eV of energy.
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At extremely high temperatures (e.g., millions of degrees), which of the following best describes the phase of matter?
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a plasma consisting of positively charged ions and free electrons
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Which of the following is a form of electrical potential energy?
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energy coming to your house from power companies.
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Which object has the most kinetic energy
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a 1-ton car moving 100 km/hr
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Suppose you heat up an oven to 400 degrees F and boil a pot of water. Which of the following explains why you would be burned by sticking your hand briefly in the pot but not by sticking your hand briefly in the oven?
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The water can transfer heat to your arm more quickly than the air.
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Which of the following scenarios involves energy that we would typically calculate with Einstein's formula E=mc2?
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When hydrogen is fused into helium, whether in the Sun or a nuclear bomb, some of the mass disappears and becomes energy.
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Suppose an atom emits a photon of light. Which of the following must have occurred within the atom?
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An electron must have dropped from a higher energy level to a lower energy level
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Which of the following statements about electrons is NOT true
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Electrons orbit the nucleus rather like planets orbiting the Sun.
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When the returning Space Shuttle enters the atmosphere and begins to slow down, its kinetic energy is primarily converted into
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thermal energy
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Gamma rays have a very small ________.
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wavelength
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Suppose you had molecular oxygen (O2) chilled enough so that it was in liquid form. Which of the following best describes the phase changes that would occur as you heated the liquid oxygen to high temperature?
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It would evaporate into a gas, then the molecules would dissociate into individual oxygen atoms, then the atoms would become increasingly ionized as you continued to raise the temperature.
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Suppose you are listening to a radio station that broadcasts at a frequency of 97 Mhz (megahertz). Which of the following statements is true?
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radio waves from the radio station are causing electrons in your radio's antenna to move up and down 97 million times each second.
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Which of the following statements is true of green grass?
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It absorbs red light and reflects green light
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The planet Neptune is blue in color. How would you expect the spectrum of visible light from Neptune to be different from the visible-light spectrum of the Sun?
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The two spectra would have similar shapes, except Neptune's spectrum would be missing a big chunk of the red light that is present in the Sun's spectrum.
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Which of the following statements about thermal radiation is always true?
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A hot object emits more radiation per unit surface area than a cool object
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Suppose a photon has a frequency of 300 million hertz (300 megahertz). What is its wavelength?
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1 meter
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Which of the following statements about electrons is not true?
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Electrons orbit the nucleus rather like planets orbiting the Sun.
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Suppose that two stars are identical in every wayfor example, same distance, same mass, same temperature, same chemical composition, and same speed relative to Earthexcept that one star rotates faster than the other. Spectroscopically, how could you tell the stars apart?
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The faster rotating star has wider spectral lines than the slower rotating star.
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Betelgeuse is the bright red star representing the left shoulder of the constellation Orion. All the following statements about Betelgeuse are true. Which one can you infer from its red color?
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Its surface is cooler than the surface of the Sun
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If we observe one edge of a planet to be redshifted and the opposite edge to be blueshifted, what can we conclude about the planet?
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The planet is rotating
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Suppose you have a 100-watt light bulb that you leave turned on for one minute. How much energy does it use?
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6,000 joules
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Consider an atom of oxygen in which the nucleus contains 8 protons and 8 neutrons. If it is doubly ionized, what is the charge of the oxygen ion and how many electrons remain in the ion?
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Charge = +2; number of remaining electrons = 6.
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Studying a spectrum from a star can tell us a lot. All of the following statements are true except one. Which statement is not true?
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The total amount of light in the spectrum tells us the star's radius.
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Which of the following statements about X rays and radio waves is not true?
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X rays travel through space faster than radio waves.
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Which of the following conditions lead you to see an absorption line spectrum from a cloud of gas in interstellar space?
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The cloud is cool and lies between you and a hot star.
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Which of the following best describes why we say that light is an electromagnetic wave?
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The passage of a light wave can cause electrically charged particles to move up and down
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No object produces a perfect thermal radiation spectrum, but many objects produce close approximations. Which of the following would not produce a close approximation to a thermal radiation spectrum?
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a hot, thin (low-density, nearly transparent) gas
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Each of the following describes an "Atom 1" and an "Atom 2." In which case are the two atoms different isotopes of the same element?
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Atom 1: nucleus with 7 protons and 8 neutrons, surrounded by 7 electrons; Atom 2: nucleus with 7 protons and 7 neutrons, surrounded by 7 electrons.
question
Suppose that Star X and Star Y both have redshifts, but Star X has a larger redshift than Star Y. What can you conclude?
answer
Star X is moving away from us faster than Star Y.
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Laboratory measurements show hydrogen produces a spectral line at a wavelength of 486.1 nanometers (nm). A particular star's spectrum shows the same hydrogen line at a wavelength of 486.0 nm. What can we conclude?
answer
The star is moving toward us.
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All of the following statements about the Sun's corona are true. Which one explains why it is a source of X rays?
answer
The temperature of the corona's gas is some 1 to 2 million Kelvin
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Which of the following best describes why radio telescopes are generally much larger in size than telescopes designed to collect visible light?
answer
Getting an image of the same angular resolution requires a much larger telescope for radio waves than for visible light.
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Which of the following best describes the development of astronomical telescopes over the past 50 years?
answer
The world's most powerful telescope remained the same for most of this period, but in the past 15 years many new and more powerful telescopes have been built.
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Suppose that the angular separation of two stars is 0.1 arcseconds, and you photograph them with a telescope that has an angular resolution of 1 arcsecond. How will the stars appear in the photograph?
answer
Since their angular separation is smaller than the telescope's angular resolution, your photograph will seem to show only one star rather than two.
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The Chandra X-ray Observatory must operate in space because:
answer
X rays do not penetrate Earth's atmosphere
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Which of the following is NOT an advantage of the Hubble Space Telescope over ground-based telescopes?
answer
It is closer to the stars.
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Which of the following is NOT a reason why telescopes tend to be built on mountaintops that are relatively far from cities and are in regions with dry climates?
answer
The thin air on mountaintops makes the glass in telescope mirrors less susceptible to warping
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The stars in our sky twinkle in brightness and color because of ______.
answer
turbulence in the Earth's atmosphere.
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How does the light-collecting area of an 8-meter telescope compare to that of a 2-meter telescope?
answer
The 8-meter telescope has 16 times the light-collecting area of the 2-meter telescope.
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Suppose you have two small photographs of the Moon. Although both look the same at small size, when you blow them up to poster size one of them still looks sharp while the other one becomes fuzzy (grainy) looking. Which of the following statements is true?
answer
The one that still looks sharp at large size has better (smaller) angular resolution than the one that looks fuzzy.
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Consider two future observatories in space. Observatory X consists of a single 50-meter telescope. Observatory Y is an interferometer consisting of five 10-meter telescopes, spread out over a region 100 meters across. Which observatory can detect dimmer stars, and which one can see more detail in its images? (Assume all else is equal, such as quality of optics, types of instruments, and so on.)
answer
Observatory X can detect dimmer stars and Observatory Y reveals more detail in images.
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Which of the following is NOT a major reason why astronomers would like an observatory on the far side of the Moon?
answer
Telescopes on the Moon could see objects in all parts of the sky equally well, whereas telescopes on Earth can see only portions of the sky that depend on their latitude.
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Suppose you point your telescope at a distant object. Which of the following is NOT an advantage of taking a photograph of the object through the telescope as compared to just looking at the object through the telescope?
answer
he photograph will have far better angular resolution than you can see with your eye.
question
Atom of carbon contains 6 protons and 7 neutrons. Atomic number and atomic mass number?
answer
atomic number = 6, mass number = 13
question
Distant galaxy. Spectral line of hydrogen has shifted from normal location in visible to infrared?
answer
Galaxy moving away
