MA 1 Introduction – Flashcards
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The Andromeda Galaxy is faintly visible to the naked eye. When you look at the Andromeda Galaxy, the retina of your eye is absorbing light that has traveled through space for ______ to reach you.
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about 2 ½ million years
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Suppose that someone in the Andromeda galaxy had a super-telescope through which they were looking at Earth right now. They would see Earth ______.
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as it was about 2 ½ million years ago
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Place each statement in the correct bin corresponding to whether it represents 1 astronomical unit (1 AU), 1 light-year, or neither of those.
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1 ASTRONOMICAL UNIT - about 150 million kilometers - Earth's average distance from the Sun - Jupiter lies about 5.2 of these from the Sun 1 LIGHT-YEAR - the distance light travels in 1 year - about 10 trillion kilometers - the star Sirius lies about 8 of these from the Sun NEITHER 1 AU NOR 1 LIGHT-YEAR -Mar's average distance from the Sun - the diameter of Earth
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Match the choices in the left-hand column to the appropriate blank in the in the right-hand column. Use each choice only once.
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Mars is about 1.5 AU from the Sun. Jupiter is about 5 AU from the Sun. The star Sirius is about 8 light-years from the Sun. The diameter of the Milky Way Galaxy is about 100,000 light-years. The distance from Earth to the Moon is less than 0.01 AU.
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In what sense are telescopes like time machines?
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They allow us to see distant objects as they were long in the past.
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Because we live in an expanding universe, distant galaxies are farther away from us today than they were when the light we see from them started on its journey to us. So what do we mean when we say that a galaxy is 7 billion light-years away?
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Its light has taken 7 billion years to reach us.
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Suppose we observe a galaxy that is 13 billion light-years away. Which of the following can we conclude?
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The galaxy formed before the universe was 1 billion years old.
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Shown here are astronomical objects located at different distances from Earth. Rank the objects based on their distances from Earth, from farthest to nearest.
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FARTHEST - star on the far side of Andromeda Galaxy - star on near side of Andromeda Galaxy - star on far side of Milky Way Galaxy - Star near center of Milky Way Galaxy -Orion Nebula - Alpha Centauri - Pluto NEAREST: Sun
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Consider again the objects you ranked by distance in Part A. Suppose each object emitted a burst of light right now. Rank the objects from left to right based on the amount of time it would take this light to reach Earth, from longest time to shortest time.
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LONGEST TIME - star on the far side of Andromeda Galaxy - star on near side of Andromeda Galaxy - star on far side of Milky Way Galaxy - Star near center of Milky Way Galaxy -Orion Nebula - Alpha Centauri - Pluto SHORTEST TIME : Sun
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Look once more at the objects you ranked in Parts A and B. This time, rank the objects from left to right based on how much they have aged since they emitted the light we see today, from greatest to least.
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AGED MOST - star on the far side of Andromeda Galaxy - star on near side of Andromeda Galaxy - star on far side of Milky Way Galaxy - Star near center of Milky Way Galaxy -Orion Nebula - Alpha Centauri - Pluto AGED LEAST: Sun
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Shown here are six galaxies, each labeled with its approximate distance from Earth. Rank the galaxies from left to right based on the amount of time it has taken their light to travel to Earth, from the longest time to the shortest time.
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LONGEST TIME - 10 billion light-years - 5 billion light-years - 2 billion light-years - 800 million light-years - 230 million light years SHORTEST TIME: 70 million light years
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Consider again the galaxies you ranked in Part A. This time, rank them from left to right based on the age of the universe at the time these galaxies emitted the light we receive from them today, from oldest (closest to today) to youngest (furthest back in time).
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OLDEST (closest to today) - 70 million light years - 230 million light years - 800 million light years - 2 billion light years - 5 billion light years YOUNGEST (furthest back in time): 10 billion light years
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Rank the following items according to their size (diameter) from left to right, from largest to smallest.
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LARGEST - the universe - the local supercluster - the Local Group - the Milky Way Galaxy - our solar system - the Sun - Jupiter SMALLEST : Earth
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Rank the following items that describe distances from longest distance (left) to shortest distance (right). (If two distances are equal, drag the second item on top of the first item.)
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LONGEST - the distance form the Milky Way Galaxy to the Andromeda Galaxy - the distance from the Sun to the center of the Milky Way Galaxy - the distance from Earth to Alpha Centauri - one light-year - the distance across our solar system (to Neptune) SHORTEST: the average distance from Earth to the Sun AND one AU
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Which of the following is not a general difference between a planet and a star?
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All planets are made of rock and all stars are made of gas.
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Our solar system consists of _________.
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the Sun and all the objects that orbit it
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A typical galaxy is a _________.
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collection of a millions or billions of stars, bound together by gravity and orbiting a common center
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Which of the following best describes what we mean by the term universe?
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The sum total of all matter and energy
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An astronomical unit (AU) is _________.
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the average distance between Earth and the Sun
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A light-year is _________.
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about 10 trillion kilometers
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A television advertisement claiming that a product is light-years ahead of its time does not make sense because _________.
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it uses light-years to talk about time, but a light-year is a unit of distance
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The term observable universe refers to _________.
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that portion of the universe that we can see in principle, given the current age of the universe
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On a scale in which the distance from Earth to the Sun is about 15 meters, the distance from Earth to the Moon is _________.
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small enough to fit within your hand
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On a scale where the Sun is about the size of a grapefruit and the Earth is about 15 meters away, how far away are the nearest stars besides the Sun?
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About the distance across the United States
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The number of stars in the Milky Way Galaxy is approximately _________.
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a few hundred billion
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What do astronomers mean by the Big Bang?
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The event that marked the beginning of the expansion of the universe
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What do we mean when we say that the universe is expanding?
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Average distances between galaxies are increasing with time.
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Based on observations of the universal expansion, the age of the universe is about _________.
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14 billion years
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What is the ecliptic plane?
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The plane of Earth's orbit around the Sun
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How long does it take the Earth to complete one orbit around the Sun?
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One year
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Consider a raisin cake expanding uniformly in an oven. Viewed from one of the raisins, you would see _____.
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all other raisins moving away from you, with more distant raisins moving faster
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Each box in this figure represents a different level of structure in our universe. Each box is labeled with one of the numbers 1-5. Which box represents the Milky Way Galaxy?
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3
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It is a picture of the Andromeda galaxy, located about 2.5 million light-years away.
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What does this photograph show?
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This painting represents the Sun and planets (and two dwarf planets) of our solar system. What is not to scale in this painting?
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The distances between the planets are not shown to scale.
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It shows a person standing on the most distant world ever visited by a human being.
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What is the significance of this photograph?
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Suppose we made a scale model of our Milky Way Galaxy in which the disk of the galaxy is the size of a football field. Which (if any) diagram represents the Sun on the same scale?
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The Sun on this scale would be microscopic and too small to see on the screen.
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These photos show two different astronomical objects. Which object is bigger, and by about how much?
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Object 2 is more than a trillion times as large as Object 1.
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This diagram represents Earth's rotation and orbit. What do we call the flat blue plane shown in this diagram?
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the ecliptic plane
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Notice that Earth's axis is shown with an arrowhead in this diagram. What does the arrow point to?
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Polaris the North Star
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These diagrams show a raisin cake before it is put in the oven and again one hour later after it has expanded during baking. Suppose you lived in Raisin 3 (the raisin labeled "3"). What would you have noticed about Raisin 2 during baking?
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Raisin 2 is moving away from you at a speed of 2 cm/hr.
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Nearly all of the objects that you can see in this photograph are:
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galaxies
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Rank the following objects from largest to smallest.
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LARGEST - galaxy -Solar System - Sun SMALLEST: Earth
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Regarding the history of the universe, which of the following is true?
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Key elements of which Earth and life are made, including carbon, oxygen, and iron, did not exist when the universe was born and were created later in stars.
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Which of the following are real motions of our "spaceship Earth"?
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-Earth and our solar system moves with the Milky Way galaxy relative to other galaxies in our Local Group. -Earth moves with the Sun on an orbit around the center of the Milky Way galaxy. - Earth orbits the Sun
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Which of the following statements about the celestial sphere is not true?
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The celestial sphere is another name for our universe.
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The Andromeda Galaxy is faintly visible to the naked eye in the constellation Andromeda. Suppose instead it were located in the same direction in space as the center of the Milky Way Galaxy (but still at its current distance). How would it appear to the eye in that case?
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We could not see it at all.
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An angle of 1 arcsecond is _________.
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less than the thickness of a human hair held at arm's length
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When traveling north from the United States into Canada, you'll see the North Star (Polaris) getting _________.
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higher in the sky
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Suppose you use the Southern Cross to determine that the south celestial pole appears 40 degrees above your horizon. Then you must be located at _________.
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latitude 40 degrees south
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Suppose you are facing north and you see the Big Dipper close to your northern horizon, with Polaris (and the Little Dipper) above it. Where will you see the Big Dipper in six hours?
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To the right of Polaris; that is, 90 degrees counterclockwise from its current position
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In any particular place on Earth, certain constellations are visible in the evening only at certain times of the year because _________.
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our evening view of space depends on where Earth is located in its orbit around the Sun
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The Sun's path, as viewed from the equator, is highest in the sky on _________.
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the March and September equinoxes
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Suppose Earth's axis tilt was significantly greater than its current 23.5 degrees, but Earth's rotation period and orbital period were unchanged. Which statement below would not be true?
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The length of each season (for example, the number of days from the summer solstice to the fall equinox) would be significantly longer than it is now.
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If our year were twice as long (that is, if Earth took twice as many days to complete each orbit around the Sun), but Earth's rotation period and axis tilt were unchanged, then _________.
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the four seasons would each be twice as long as they are now
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How does Earth's varying distance from the Sun affect our seasons?
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It doesn't; Earth's orbital distance plays no significant role in the seasons.
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Suppose you live in the United States and you see a crescent moon in your evening sky tonight. What will a friend in South America see tonight?
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Your friend will also see a crescent moon.
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Suppose it is full Moon. What phase of Earth would someone on the Moon see at this time?
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new Earth
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It's 6 a.m. and the Moon is at its highest point in your sky (crossing the meridian). What is the Moon's phase?
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third quarter
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You observe a full Moon rising at sunset. What will you see at midnight?
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A full moon high in the sky
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All the following statements are true. Which one explains the reason that there is not a solar eclipse at every new moon?
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The orbital plane of the Moon is tilted slightly (by about 5 degrees) to the ecliptic plane.
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For most of history, the lack of observable stellar parallax was interpreted to mean that _________.
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Earth is stationary at the center of the universe
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During the period each year when we see Mars undergoing apparent retrograde motion in our sky, what is really going on in space?
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Earth is catching up with and passing by Mars in their respective orbits.
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Suppose you see a photo showing Jupiter half in sunlight and half in shadow (that is, a first-quarter Jupiter). This photo might have been taken by _________.
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the Galileo spacecraft that orbited Jupiter in the 1990s
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About how many stars are visible to the naked eye on a clear, dark night away from city lights?
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a couple thousand
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What do astronomers mean by a constellation?
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A constellation is a region in the sky as seen from Earth.
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What is the ecliptic?
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The path the Sun appears to trace around the celestial sphere each year
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What is the celestial sphere?
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The celestial sphere is a representation of how the entire sky looks as seen from Earth.
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What do we mean when we talk about the Milky Way in our sky?
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The patchy band of light that outlines the plane of the Milky Way Galaxy as seen from Earth.
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Which of the following statements does not use the term angular size or angular distance correctly?
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The angular distance between those two bright stars in the sky is about 2 meters.
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Which of the following correctly describes the meridian in your local sky?
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A half-circle extending from your horizon due north, through your zenith, to your horizon due south
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The point directly over your head is called _________.
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the zenith
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Stars that are visible in the local sky on any clear night of the year, at any time of the night, are called _________.
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circumpolar
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We describe a location on Earth's surface by stating its _________.
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latitude and longitude
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If you are located in the Northern Hemisphere, which of the following correctly describes a relationship between the sky and your location?
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The altitude of the north celestial pole equals your latitude.
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Which of the following best describes why we have seasons on Earth?
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The tilt of Earth's axis causes different portions of the Earth to receive more or less direct sunlight at different times of year.
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Each choice describes how a few astronomical phenomena are related to time periods. Which list is entirely correct? (Careful: some lists are partially correct.)
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Earth's rotation defines a day. The cycle of the Moon's phases takes about a month. Earth's orbit defines a year. Earth's cycle of axis precession takes 26,000 years.
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If we have a new moon today, when we will have the next full moon?
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In about two weeks
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We cannot see a new moon in our sky because _________.
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a new moon is quite near the Sun in the sky
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The Moon always shows nearly the same face to Earth because ________.
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the Moon rotates once in the same amount of time that it takes the Moon to orbit Earth once
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Lunar eclipses can occur only during a _________.
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full moon
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What is the saros cycle?
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The roughly 18-year cycle over which the pattern of eclipses repeats
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During the time that a planet is in its period of apparent retrograde motion: _________
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Over many days or weeks, the planet moves westward relative to the stars, rather than the usual eastward relative to the stars
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What is stellar parallax?
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It is the slight back-and-forth shifting of star positions that occurs as we view the stars from different positions in Earth's orbit of the Sun.
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This diagram represents a simplified model of the celestial sphere. The unlabeled circle that is highlighted in purple represents:
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celestial equator
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This diagram represents a person's local sky. What does the red semicircle represent?
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the meridian
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What is the approximate latitude and longitude of the South American location marked by the black dot on this diagram?
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latitude = 15ºS, longitude = 45ºW
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Diagrams like this one are commonly used in discussions of seasons and they can be quite useful. However, this diagram greatly exaggerates:
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all of the answers listed
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Which position in this diagram represents Earth on the day that we have the longest amount of daylight in the continental United States?
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2
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Which position in this diagram represents Earth at the beginning of spring for the Southern Hemisphere?
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3
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Which photo shows what we call a first-quarter moon?
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2
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Which photo shows what we call a gibbous moon?
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3
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This multiple exposure photograph shows the apparent retrograde motion of Mars. To make this picture, the photographer needed to combine individual photos of Mars taken over a period of:
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several months
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What is this a picture of?
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a total solar eclipse
