Astro Ch 1-5 – Flashcards
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The word astronomy:
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means "patterns among the stars"
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In 2006, Pluto's status was changed from a classical planet to a dwarf planet primarily because of its:
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small size
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We are located approximately:
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halfway out from the center of the Milky Way
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Light from the Sun takes about __________ to reach Earth.
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8 minutes
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If an event were to take place on the Sun, how long would it take for the light to reach us?
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8 minutes
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After the Sun, the next nearest star to us is approximately __________ away.
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4 light-years
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One of the nearest stars is Alpha Centauri, whose distance is 4.4 light-years. The time it takes light to travel from Alpha Centauri to us is:
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4.4 years
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The distance to the nearest large spiral galaxy, Andromeda, is 2.5 million light-years. How long does it take light to travel from us to Andromeda?
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2.5 million years
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The early universe was composed mainly of which two elements?
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Hydrogen and helium
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Our universe is approximately __________ years old.
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14 billion
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The number of classical planets in the Solar System is:
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eight
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Which of the following most closely approximates the number of stars in the Milky Way?
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100 billion
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The speed of light is about:
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300,000 km/s
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A light-year is measured in units of:
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distance
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The most massive elements (such as those that make up rocky planets like Earth) were formed:
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inside stars and supernovae
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What are the advantage(s) of placing telescopes in space?
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All of the above
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If you were to specify your address in the universe, listing your membership from the smallest to largest physical structures, it would be:
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Earth, Solar System, Milky Way, Local Group, Virgo Supercluster, the universe
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If the diameter of our galaxy is approximately 100,000 light-years, our galaxy is __________ times larger than our Solar System.
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106
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The Local Group is the environment around:
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the Milky Way that contains a few dozen galaxies
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Which of the following is FALSE?
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The Milky Way galaxy contains approximately 100 million stars.
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If you compared the diameter of the Earth (13,000 km) to 1 second, what unit of time would be equivalent to the size of our Galaxy, whose diameter is 1.5 × 1021 m __________, which is the length of time between now and when __________.
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4 billion years; the Solar System was born
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Measuring distances in the amount of time it takes light to travel, if the circumference of Earth is a snap of your fingers, the diameter of the Solar System is approximately equal to:
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the time between sunrise and sunset
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A scientific theory can be proven wrong if:
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scientists gather new data that disprove its predictions
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Albert Einstein is best known for his revolutionary theory of:
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relativity
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Which of the following is FALSE?
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A scientific theory is an undisputed fact.
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The scientific method is a process by which scientists:
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gain confidence in theories by failing to prove them wrong
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A __________ becomes a __________ when repeated testing of its predictions does not disprove it.
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hypothesis; theory
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The cosmological principle states that:
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the universe looks the same everywhere as long as you look on large enough spatial scales
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__________ is the idea that the simplest explanation for a phenomenon is usually the correct one.
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Occam's razor
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One of the central assumptions in astronomy is that the physical laws of nature:
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are the same everywhere in the universe
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When you see a pattern in nature, it is usually evidence of:
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an underlying physical law
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The language of science is:
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mathematics
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Scientific notation allows us to:
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write very large and very small numbers in a convenient way
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The kind of mathematics that deals with change is called:
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calculus
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Write 3,800,000,000 in scientific notation.
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3.8 × 10^9
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Write 0.00000037 in scientific notation.
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3.7 × 10^-7
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Approximately how many feet are in 4 m?
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12
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How many nanometers are in a millimeter?
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1,000,000
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Approximately how many meters are in 12 ft?
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4
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When we say that "we are stardust"
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we mean that previous generations of stars formed all the material in our Solar System.
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In order to describe the patterns we observe in the sky, we use the language of
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mathematics.
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Most of what we know about the objects in our Solar System has been discovered by
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images and other data acquired from unmanned probes.
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Einstein's special and general theories of relativity may be considered
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a scientific revolution.
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Which of the following are in order from smallest to largest?
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the Milky Way Galaxy, the Local Group, the Virgo Supercluster
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Scientific knowledge is reliable because
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predictions are measured against experiments and observations.
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For light from the Sun to reach the closest star to our Sun, it takes
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about four years.
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The ultimate tester of the correctness of scientific knowledge is
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nature.
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What is the Cosmological Principle?
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The proposition that natural laws should behave the same everywhere in the Universe
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Which of the following phrases should a scientist probably not use in talking about the production of scientific knowledge?
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absolute truth
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How do we test scientific knowledge?
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We try to see if it is wrong.
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Where did the vast majority of chemical elements found on Earth come from?
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Chemical elements are formed in the core of stars.
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Occam's razor is a guiding principle that states
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when two hypotheses explain a phenomenon well, the simplest explanation is the best.
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The age of the Universe is about
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3 times the age of Earth.
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How quickly does light travel?
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around Earth in a fraction of a second
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Which of the following are used in astronomy?
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all of the above.
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A scientific theory that is well tested may be referred to as
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a physical law.
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Compared to other stars, we find the Sun remarkable because of
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it is the star that the Earth orbits.
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Which of the following lists of sizes are in order from smallest to largest?
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Neptune's orbit, the diameter of our galaxy, the size of the Universe
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Light travels across the diameter of the Solar System in
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8 hours.
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What is astrobiology?
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a study of the possibilities that life exists elsewhere besides Earth
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About how many galaxies are in the universe?
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several hundred billion
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The number 384,000,000 can also be written as
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3.84 × 108.
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When using the scientific method, a hypothesis that would explain a particular observation
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must be able to be tested.
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Our complete cosmic address is
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Earth, Solar System, Milky Way Galaxy, Local Group, Virgo Supercluster.
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he direction directly overhead of an observer defines his/her:
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zenith
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No matter where you are on Earth, stars appear to rotate about a point called the:
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celestial pole
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If the star Polaris has an altitude of 35° then we know that:
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our latitude is +35°
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At a latitude of +50°, how far above the horizon is the north celestial pole?
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50°
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The meridian is defined as a great circle on the sky on which lie the:
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zenith and the north and south celestial poles
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At what latitude is the north celestial pole located at your zenith?
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+90°
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At what latitude is the north celestial pole at your horizon?
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0°
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The apparent path of the Sun across the celestial sphere during a year is called the:
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ecliptic plane
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The ecliptic plane is defined by the motion of __________ in the sky. the Moon
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the Sun
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How far away on average is the Earth from the Sun?
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150 million kilometers
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If you go out at exactly 9 P.M. each evening over the course of one month, the position of a given star will move westward by tens of degrees. What causes this motion?
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The revolution of the Earth around the Sun
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The shortest day of the year for a person living in the NORTHERN Hemisphere is the:
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winter solstice
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On which day of the year does the Sun reach its northernmost point in the sky?
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Summer solstice
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When the Northern Hemisphere experiences summer, the Southern Hemisphere experiences:
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winter
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The Earth's rotational axis precesses in space and completes one revolution every:
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26,000 years
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Leap years occur because:
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the Earth's orbital period is 365.24 days
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If the Earth's axis were tilted by 5° relative to the direction perpendicular to its orbital plane around the Sun, which would be TRUE?
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Winters would be warmer.
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We experience seasons because:
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the Earth's equator is tilted relative to the plane of the solar system
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If you went out tonight and looked at the sky at midnight, at what time would you have to observe 6 months from now in order to find the stars in exactly the same position in the sky? Assume that you could see the stars at any time, day or night.
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Noon
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The shortest day of the year for a person living in the SOUTHERN Hemisphere is the:
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summer solstice (June 1)
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For a person who lives at a latitude of +40°, when is the Sun directly overhead at noon?
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Never
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The Moon undergoes synchronous rotation, and as a consequence the:
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rotational period of the Moon equals the orbital period of the Moon around the Earth
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In regard to the phase of the Moon, the term waxing means:
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increasing in brightness
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If tonight the Moon is in the waxing gibbous phase, in three days the Moon will most likely be in the:
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full phase
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If there is a full Moon out tonight, approximately how long from now will it be in the third quarter phase?
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One week
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Which of the following is FALSE?
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The observed phase of the Moon changes over the course of one night.
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At what time does a third quarter Moon rise? (Hint: A third quarter Moon occurs approximately 3 weeks after a new Moon.)
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12 midnight
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What time does a third quarter Moon rise?
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12 midnight
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At what time does the waxing gibbous phase rise?
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3 P.M.
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If a person on Earth currently views the Moon in a waxing crescent phase, in what phase would the Earth appear to a person on the Moon?
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Waning gibbous
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During which lunar phase do solar eclipses occur?
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New
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A partial lunar eclipse occurs when:
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the Moon passes through part of the Earth's shadow
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Solar and lunar eclipses are rare because:
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the Moon's orbital plane is tipped by 5.2° relative to the Earth's orbital plane
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Approximately how often do lunar eclipses occur?
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Twice every 11 months
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When the Earth catches up to a slower moving outer planet and passes it in its orbit like a faster runner overtakes a slower runner in an outside lane, the planet:
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exhibits retrograde motion
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If the Sun is located at one focus of Earth's elliptical orbit, what is at the other focus?
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Nothing
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The average distance between a planet and the Sun is given by the __________ of its elliptical orbit.
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semimajor axis
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Which of the following is TRUE about a comet that is on an elliptical orbit around the Sun?
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The comet's speed is greatest when it is nearest the Sun.
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The time it takes a planet to complete one full orbital revolution is commonly known as its:
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period
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Kepler's third law is a relationship between an orbiting object's:
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period and semimajor axis
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A circle has an eccentricity of __________ and a line has an eccentricity of __________.
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0; 1
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If you travel 20 miles from home to school in 30 minutes, what is your average velocity?
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40 mph
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Kepler's third law can be expressed mathematically as:
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P2 = A3
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Suppose an asteroid had an orbit with a semimajor axis of 4 AU. How long would it take for it to orbit once around the Sun?
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8 years
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If Jupiter has an orbital period of 12 years, what is its average distance from the Sun?
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5 AU
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If you are located at a position of latitude 30° north, a star that you observe near the north celestial pole will
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stay up longer than a star located on the celestial equator.
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In six months, you will be able to see a different set of stars in the night sky because
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the Earth will move.
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If it is 6:00 PM where you live and you see a full Moon, it is
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"rising" from the eastern horizon.
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If Earth's axis were tilted twice as much as it currently is, we would experience
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larger changes in seasons.
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We only see one side of the Moon because
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the Moon rotates on its axis once per revolution around Earth.
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Residents of the Southern Hemisphere cannot see the stars around the north celestial pole because
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Earth itself is in the way.
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Is there any location on Earth where the entire sky is potentially visible within a 24-hour period (ignoring the fact that some stars can't be seen if it is daytime)?
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At the equator
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From the equator, stars at night will seem to
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rise in the east, move overhead, and then set in the west.
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The precession of the equinoxes is due to
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the wobble of the Earth as it spins on its axis.
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When the Sun crosses the meridian at your location on Earth, it is
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local noon.
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A lunar eclipse is possible
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only when a full Moon intersects the line of nodes.
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Jupiter takes longer to move around the Sun than Earth does because
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both a and b
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Comparing a solar eclipse to a lunar eclipse,
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the solar eclipse is visible over less of the Earth's surface than a lunar eclipse.
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Kepler's second law, the law of equal areas, states that
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a planet moves its fastest when closest to the Sun.
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Copernicus is famous for reviving what ancient Greek idea?
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The idea that the Earth orbits the Sun
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The eccentricity of most planets in our Solar System is
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close to 0, nearly circular.
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From the perspective of a viewer in the Northern Hemisphere, which of the following is most true?
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The north celestial pole is always somewhere overhead.
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The time it takes a planet to complete its orbit is determined by
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its distance from the Sun.
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A sky observer in the Southern Hemisphere would
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see stars moving clockwise around the south celestial pole.
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The tilt of Earth's axis affects seasons by
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changing the inclination of sunlight upon your location on Earth as the year progresses.
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A line running from due north to due south through a point directly overhead is called
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a meridian.
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Your likelihood of seeing a particular phase of the Moon depends on
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all of the above
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A crescent phase of the Moon can be seen at midnight if the Moon is
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This situation is impossible; you cannot view this phase at this time.
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The Sun is directly overhead at noon
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only twice a year at locations within the Tropics.
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An ellipse has no more than
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2 foci.
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What force holds planets in their orbits?
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Gravity
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Which scientist ended up under house arrest due to his support of the heliocentric model?
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Galileo Galilei
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In the absence of air friction, a 0.001-kg piece of paper and a 0.1-kg notebook are dropped from the same height and allowed to fall to the ground. How do their accelerations compare?
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The accelerations are the same.
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In which of the following situations would the object be experiencing an unbalanced force?
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An car moving at constant speed turning a corner
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Which of the following did NOT require the use of a telescope to observe?
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Retrograde motion of the planets
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An empirical science is one that is based on:
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observed data
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__________ hypothesized that planetary motions could be explained by a force arising from the attraction between the mass of the planet and Sun that decreased with the square of the distance between them.
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Isaac Newton
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Newton's first law states that objects in motion:
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stay in motion
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If an object is moving in a circular orbit at a constant speed, which of the following is FALSE?
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Its acceleration is zero.
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Two rocks (call them S and T) are a distance of 50 km from one another. Rock S has 20 times the mass of rock T. Which rock will move faster if the only force involved is their mutual gravitational attraction?
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Rock T
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Which of Newton's Laws states that if an unbalanced force acts on an object, then the object's motion changes?
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Newton's 1st Law
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The natural tendency of an object to resist changes in motion is called:
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inertia
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In a spaceship orbiting Earth, two astronauts want to measure the mass of a mouse. How can they easily do it if they are in constant free fall?
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Push on the mouse with a known force and measure its acceleration.
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If a 100-kg astronaut pushes on a 5,000-kg satellite and the satellite experiences an acceleration of 0.1 m/s2, what is the acceleration experienced by the astronaut in the opposite direction?
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5 m/s2
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The force of gravity that an object has is directly related to its:
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mass
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Which of the following properties of an astronaut changes when he/she is standing on the Moon, relative to when the astronaut is standing on Earth?
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Weight
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Your weight is directly proportional to your ___________.
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mass
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If your weight on Earth was 500 N, what would your weight be on the Moon?
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83 N
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Which of the following is true about a comet that is on an elliptical orbit around the Sun?
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The comet's speed is greatest when it is nearest the Sun.
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What type of orbit results when a satellite has a velocity greater than the escape velocity?
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Unbound
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Once a satellite's velocity at closest approach equals or exceeds the __________ velocity, it is in an unbound orbit.
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escape
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Which of the following is NOT an example of a satellite of the Earth?
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The Sun
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Astronauts orbiting Earth in the space shuttle feel weightless in space because:
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they are in constant free fall around the Earth
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If we wanted to increase the Hubble Space Telescope's altitude above the Earth and keep it in a stable orbit, we also would need to:
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decrease its orbital speed.
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What two pieces of information do we need to know about the Earth in order to calculate the mass of the Sun?
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The semimajor axis of the Earth's orbit is 1 AU and the Earth takes 1 year to orbit the Sun.
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You apply a force of 10 N to a grocery cart in order to get an acceleration of 0.5 m/s2. If you apply a force of 20 N to the same grocery cart, its acceleration will be:
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1 m/s2
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What is your acceleration if you go from 0 to 30 m/s in 3 seconds?
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10 m/s2
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What is your acceleration if you go from 0 to 60 mph in 4 seconds?
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15 mph/s
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If the distance between the Earth and Sun were cut in half, the gravitational force between these two objects would:
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increase by 4
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Suppose you are suddenly transported to a planet with 1/4 the mass of Earth but the same radius as the Earth. Your weight would __________ by a factor of __________.
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decrease; 4
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Suppose you are suddenly transported to a planet with 1/4 the radius of Earth but the same mass as the Earth. Your weight would __________ by a factor of __________.
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increase; 16
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If you weighed 150 lbs on Earth, what would you weigh on Mars? For reference, Mars has a mass that is 0.1 times the Earth's mass and Mars has a radius that is 0.5 times the Earth's radius.
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60 lbs
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The force of gravity between the Earth and the Sun is __________ the force of gravity between the Earth and the Moon. For reference, the average distance between the Earth and the Moon is 0.003 AU, the mass of the Moon is 7 × 1022 kg, and the mass of the Sun is 2 × 1030 kg.
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260 times larger than
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If a satellite is moving at the slowest velocity above the Earth to just orbit our planet,
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its orbit is circular.
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a student tosses a rock upward,
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the rock will rise at a constant speed but increase in speed as it falls back.
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When traveling in a car and suddenly braking for a red stoplight,
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the driver is undergoing acceleration because the car is slowing down.
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Which of the following is a type of force?
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Weight
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According to Newton's first law, a space probe traveling through interplanetary space will
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maintain its motion without any outside force.
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When we say a satellite is orbiting a planet we mean that
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the satellite is falling freely around the planet.
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Chris, a space shuttle astronaut, is involved in repairing a satellite while in Earth orbit, but he becomes separated from the space shuttle. He has a massive wrench in his hand. What should he do to return to the space shuttle?
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Throw the wrench exactly opposite to the direction of the space shuttle.
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If two objects are dropped from the same height, which of the following outcomes will most likely take place?
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Both objects will land at the same time.
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Newton's law of universal gravitation is significant because
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it can be applied to any orbit in the universe to calculate the mass of the object being orbited.
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The gravitational force between Earth and yourself depends upon
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both a and b
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Newton's first law states:
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An object in motion tends to stay in motion in the same direction until an unbalanced force acts upon it.
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If the velocity of a comet at its closest approach to the Sun is more than its escape velocity,
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its orbit about the Sun will be unbound.
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Forces always occur
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simultaneously in pairs.
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A measurement of an object's inertia is made via its
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mass.
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We apply Newton's law of gravity to
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all of the above
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Galileo's work on the motion of an object was significant because
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he conducted experiments with moving objects to verify his rules of motion.
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The first observational evidence that some objects in the sky did not orbit Earth was
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Galileo's discovery that Jupiter's moons were near the planet.
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Astronauts in orbit around Earth feel weightless because
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they are falling around the Earth.
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"Escape velocity" refers to
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the lowest velocity required for an object to assume a path where it never returns.
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Which of the following objects is accelerating?
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A ball moving at a constant rate around a circular hoop
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Who first discovered Newton's first law?
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Galileo
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Sandy, a space shuttle astronaut, pushes on a bowling ball twice as hard as Doug, another space shuttle astronaut.
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The acceleration of the ball that Sandy causes is twice as great as Doug's acceleration.
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If Earth were twice as far from the Sun as it is now, the gravitational force between Earth and the Sun would be
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0.25 times as great.
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Galileo observed that Venus had phases, with the full phase occurring when Venus appeared smaller. This implied that
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the heliocentric model of the Solar System was correct.
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Which of these does not determine the acceleration of a falling body on Earth?
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The mass of the falling body
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The speed of light was first determined by which scientist?
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Rømer
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The speed of light in a vacuum is __________.
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300,000 km/s
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How does the speed of light traveling through a medium (such as air or glass) compare to the speed of light in a vacuum?
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It is always less than the speed of light in a vacuum.
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The light-year is a unit of:
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distance
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How do the wavelength and frequency of red light compare to the wavelength and frequency of blue light?
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Red light has a longer wavelength and lower frequency than those of blue light.
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The fact that the speed of light is constant (as it travels through a vacuum) means that:
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photons with longer wavelengths have lower frequencies
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Light with a wavelength of 600 nm has a frequency of:
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5.0 × 1014 Hz
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Why is an iron atom a different element than a sodium atom?
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An iron atom has more protons in its nucleus than a sodium atom.
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Which of the following photons carry the least amount of energy?
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A microwave photon, whose wavelength is 10^-2 m
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A red photon has a wavelength of 650 nm. An ultraviolet photon has a wavelength of 250 nm. The energy of an ultraviolet photon is __________ than a red photon.
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2.6 times larger
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As wavelength increases, the energy of a photon __________ and its frequency __________.
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decreases; decreases
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One reason to prefer a reflecting over a refracting telescope is its:
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All of the above are valid reasons.
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A prism is able to spread white light out into a spectrum of colors based on the property of:
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refraction
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Why do reflecting telescopes usually have a secondary mirror in addition to a primary mirror?
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To make the telescope shorter
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As a beam of light travels from one medium to another, the change in direction of the beam of light depends on:
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all of the above
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The light-gathering power of a 4-m telescope is __________ than that of a 2-m telescope.
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4 times larger
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Which telescope would collect 100 times more light than a 1-m telescope?
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10-m telescope
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Which of the following lists different types of electromagnetic radiation in order of increasing wavelength?
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Gamma rays, ultraviolet, visible, infrared, radio waves
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Before CCDs were invented, what was the device most commonly used for imaging with optical telescopes?
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Photographic glass plates
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How does the resolution of a telescope depend on its focal length?
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The longer the focal length, the better the resolution.
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The part of the human eye that acts as the detector is the:
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retina
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Photography provides an improvement over naked-eye observations because:
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it is possible to detect fainter objects with the use of photographic plates
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The major advantage CCDs have over other imaging techniques is that:
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All of the above are true
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The angular resolution of a ground-based telescope is usually set by:
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atmospheric seeing
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Cameras that use adaptive optics provide higher spatial resolution images primarily because:
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deformable mirrors are used to correct the blurring due to the Earth's atmosphere
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Arrays of radio telescopes can produce much better resolution than single-dish telescopes because they work based on the principle of:
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interference
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When we determine the angular resolution of an interferometric array of radio telescopes using the formula q µ l/D, the variable D stands for the:
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separation between the telescopes
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Which of the following causes the biggest problem in detecting infrared photons from an astronomical object?
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Water vapor
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The 305-m Arecibo radio telescope in Puerto Rico has a resolution that is closest to that of:
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a human eye (1 arcmin)
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Ultraviolet radiation is hard to observe primarily because:
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the Earth's atmosphere easily absorbs it
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The Voyager I spacecraft is currently 16.5 billion km from Earth and heading out of our Solar System. How long does it take radio messages from Voyager I to reach us?
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15 hours
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The SETI project's Allen Telescope Array will have 350 radio dishes, each with an individual diameter of 6 m, spread out over a circle whose diameter is 1 km. What would this array's spatial resolution be when it operates at 6,000 MHz?
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10 arcsec
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The two Keck 10-m telescopes, separated by a distance of 85 m, can operate as an interferometer. What is its resolution when it observes in the infrared at a wavelength of 2 microns?
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0.006 arcsec
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If the wavelength of a beam of light were to double, how would that affect its frequency?
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The frequency would be two times smaller.
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Which formula denotes how the speed of light is related to its wavelength and frequency?
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c = ?f
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The diffraction limit of a 4-m telescope is __________ than that of a 2-m telescope
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2 times smaller
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The angular resolution of the largest single-dish radio telescope in the United States, the 300-ft Green Bank Telescope, is __________ when it operates at a wavelength of 20 cm.
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0.12°
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Adaptive optics is a technique used to correct telescope images for
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atmospheric distortion.
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Astronomical seeing depends on
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the turbulent distortions of the Earth's atmosphere.
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How do we get most of our knowledge about our Universe?
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through observation of light from astronomical objects
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Radio telescopes suffer from poor resolution because
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radio waves have such a large wavelength compared to the diameter of the telescope.
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Resolution isv
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how clearly two objects are separated.
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Which of these ranges of electromagnetic radiation has the longest wavelengths?
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radio waves
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Which of the following photons of electromagnetic radiation carry the highest energy?
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gamma rays
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What is a major disadvantage of refractors?
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The lens is subject to chromatic aberration.
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A larger image size is achieved by
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increasing the focal length of the lens of a telescope.
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The Spitzer Space Telescope
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is in a solar orbit because it needs to be far from the Earth.
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Energy of light is proportional to its
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frequency.
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The frequency of a wave is defined as
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the number of wave crests passing a point in space each second.
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The resolution achievable by an unaided human eye is
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one arcminute.
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The Hubble Space Telescope
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is in a low-Earth orbit.
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As light's wavelength decreases
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its frequency increases.
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Today, the best device for detecting the light from a telescope is
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the charge coupled device (CCD).
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Light can be generally described as
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an electromagnetic wave.
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Which of these ranges of electromagnetic radiation has the shortest wavelengths?
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X-rays
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A light year is
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the distance traveled by light in one year.
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From the absorption or emission lines in the spectrum of an object's light, it is possible to determine
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the type of atoms in the object.
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Light is a means of transporting
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energy.
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An interferometer is
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two or more telescopes acting as one instrument.
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There is an atmospheric window for
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radio waves.
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The advantages of an interferometer are
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improved resolution.
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Romer found that he measured different times for the disappearance of moons behind Jupiter, demonstrating that
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it took light a measurable amount of time to travel.
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According to the conservation of angular momentum, if an ice skater starts spinning with her arms out wide, then slowly pulls them close to her body, this will cause her to:
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spin faster
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Which of the following is NOT a characteristic of the early Solar System, based on current observations?
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The composition of gases varied between the inner Solar System and the outer Solar System.
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How much mass was there in the protoplanetary disk out of which the planets formed, compared to the mass of the Sun?
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; 1 percent
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What happens to the gravitational energy of gas as it falls toward and eventually hits the accretion disk surrounding a protostar?
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It is converted into thermal energy, heating the disk.
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What sets the temperature of the pocket of gas in a protoplanetary disk?
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All of the above
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How much material in an accretion disk goes into forming the planets, moons, and smaller objects?
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A small amount of it
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Conservation of angular momentum slows a cloud's collapse:
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mostly along directions perpendicular to the cloud's axis of rotation
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If a collapsing interstellar cloud formed only a protostar without an accretion disk around it, what would happen?
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The forming protostar would be rotating too fast to hold itself together.
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The solid form of a volatile material is generally referred to as a(n):
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ice
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The primary atmospheres of the planets are made mostly of:
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hydrogen and helium
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The difference in composition between the giant planets and the terrestrial planets is most likely caused by the fact that:
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the terrestrial planets are closer to the Sun
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Whether or not a planet is composed mostly of rock or gas is set by
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all of the above
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The atmosphere of which of these planets is primary, as opposed to secondary, in origin?
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Saturn
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Why do outer planets like Jupiter have huge gaseous atmospheres of hydrogen and helium while the inner planets do not?
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The outer planets grew massive quickly enough to gravitationally hold on to these gases before the solar wind dispersed the accretion disk.
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Comets and asteroids are:
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material left over from the formation of the planets
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The Moon probably formed:
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out of a collision between the Earth and a Mars-sized object
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Which of the following is NOT considered evidence of cataclysmic impacts in the history of our Solar System?
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Valles Marineris on Mars is a huge scar, many times deeper than the Grand Canyon, which spans one-fourth the circumference of the planet.
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Was it ever possible (or is it currently possible) for Jupiter to become a star?
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No, it would have to be at least 80 times more massive.
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Two competing models of the formation of giant gaseous planets suggest they form either from gas accreting onto a rocky core or from:
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fragmentation of the accretion disk surrounding the protostar
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What prevented the Moon from maintaining any atmosphere with which it originally formed?
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It is not massive enough.
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Most planets currently found around other stars are:
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comparable in mass to Neptune or more massive
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The Doppler shift can be used to determine the __________ of an object.
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radial velocity
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Astronomers believe that the "hot Jupiters" found orbiting other stars must have migrated inward over time by:
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losing orbital angular momentum
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The borderline between the most massive planet and the least massive brown dwarf occurs at:
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13 Jupiter masses
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Have astronomers detected any Earth-sized planets around normal stars yet?
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No, we do not have the technology to detect such low-mass planets yet.
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An observer outside our solar system, who monitors the velocity of our Sun over time, will find that its velocity varies by +/- 12 m/s over a period of 12 years, because of:
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Jupiter's gravitational pull
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Why have astronomers found more Jupiter-sized planets at a distance of 1 AU around other stars than Earth-sized planets?
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A Jupiter-sized planet exerts a larger gravitational force on the star than an Earth-sized planet, and the Doppler shift of the star is larger.
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Detecting a planet around another star using the transit method is difficult because:
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the planet must pass directly in front of the star
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Which of the following is FALSE?
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No extra-solar planets have been imaged directly to date; all have been found by indirect methods.
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Astronomers have used radial velocity monitoring to discover:
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extra-solar planetary systems that contain more than one planet
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When astronomers began searching for extra-solar planets, they were surprised to discover Jupiter-sized planets much closer than 1 AU from their parent stars. Why is this surprising?
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These planets must have formed at larger radius where temperatures were cooler and then migrated inward.
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What is the best method to use to detect Earth-sized extra-solar planets with the telescopes and instrumentation that exist today?
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Microlensing
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What is the ratio of the orbital angular momentum of the Earth compared to its spin angular momentum? Note that the Earth has a radius of 6,000 km, and 1 AU is 1.5 × 10^11 m.
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4 million
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What is the ratio of the orbital angular momentum of Jupiter to its spin angular momentum? Jupiter's orbit has a semimajor axis of 5 AU and a period of 12 years, and Jupiter has a rotation period of 0.4 day and a radius of 70,000 km.
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26 thousand
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If an interstellar cloud having a diameter of 10^16 m and a rotation period of a million years were to collapse to form a sphere that had the diameter of our solar system, 40 AU, what would its rotation period be?
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4 months
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You record the spectrum of a star and find that the calcium absorption line, whose rest wavelength is 393.3 nm, has an observed wavelength of 394.0 nm. What is the radial velocity of this star?
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500 km/s
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You are driving on the freeway when a police officer records a shift of -7 nm when he hits you with a radar gun that operates at a wavelength of 0.1 m. How fast were you going?
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47 mph
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A primary atmosphere around a planet is formed from
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capture of gas from the protoplanetary disk.
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A protostar is
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an early form of a star in development.
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An object that is redshifted is
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moving away from us.
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Asteroids are
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planetesimals that never came together to form a major planet.
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A most likely scenario for the formation of Earth's Moon was that
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it was the result of a large impact on Earth.
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A brown dwarf
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is a body with a mass greater than the upper limit for planets but less than the mass of the smallest star.
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Compared to the Sun, a typical protostar will be
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more luminous.
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In the outer accretion disk of the early Solar System,
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there were lower temperatures in which both volatile and refractory materials existed.
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Why are a large number of discovered extrasolar planets comparable to the mass of Jupiter and orbiting close to their parent star?
answer
Hot Jupiters are easier to detect.
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As a rotating object pulls more mass toward its center of rotation,
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its angular momentum stays the same and its rotational speed increases.
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Comet nuclei are found mostly
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far from the Sun and mostly beyond the giant gas planets.
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Evidence that our own Solar System formed from a protoplanetary disk is that
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the orbits of the eight planets are almost perfectly in the same plane.
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Materials that remain solid at high temperatures are called
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refractory materials.
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Angular momentum depends upon
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all of the above
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The formation of planets
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seems to be a standard part of star formation.
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Which of the following are not conserved quantities?
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force
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As a large planet orbits a star,
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Both b and c
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A brief brightening of a star could be caused by
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a gravitational lens effect of a massive, unseen planet.
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Before the planets were formed, the cloud from which our Solar System originated
answer
formed a rotating disk.
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How do molecular cloud cores collapse?
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The inside of molecular cloud core has a stronger self-gravity than the exterior and begins the collapse from the inside.
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As a protostar evolves,
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it becomes smaller and hotter because its increasing mass compresses and heats up its interior.
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A protostar should be most visible in
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infrared light.
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An example of volatile material is
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ammonia.
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Which of the following would promote the collapse of a cool, dense interstellar cloud?
answer
self-gravity
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Terrestrial planets formed from
answer
planetesimals containing only rock and metals.
