Astronomy 10 Final Practice – Flashcards
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Which of the following has your "address" in the correct order?
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you, Earth, solar system, Milky Way, Local Group, Local Supercluster
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Rougly how many stars are in the Milky Way Galaxy?
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100 Billion
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Which of the following statements about the celestial sphere is not true?
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The "celestial sphere" is just another name for our universe
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Which of the following statements about the celestial equator is true at all latitudes?
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It represents an extension of Earth's equator onto the celestial sphere.
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What is the ecliptic?
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the Sun's apparent path along the celestial sphere.
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Which of the following correctly describes the meridian in your 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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How many arcseconds are in 1 degree?
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3,600
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What is a circumpolar star?
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a star that always remains above your horizon
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Which of the following is not a phase of the Moon?
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half Moon
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If the moon is setting at 6 A.M, the phase of the Moon must be
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Full
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How did Eratosthenes estimate the size of the Earth in 240 B.C.?
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by comparing the maximum altitude of the sun in two cities at different latitudes
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Where was the sun in Ptolemy's model of the universe?
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between the orbits of Venus and Mars
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The controversial book of this famous person, published in 1543 ( the year of his death ), suggested that Earth and other planets orbit the Sun.
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Copernicus
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He discovered that the orbits of planets are ellipses.
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Kepler
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He dioscovered that Jupiter has moons.
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Galileo
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If your mass is 60 kg on Earth, what would your mass be on the Moon?
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60 kg
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What would happen if the Space Shuttle were launched with a speed greater than Earth's escape velocity?
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It would travel away from Earth into the solar system
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The force of gravity is an inverse square law. This means that, if you double the distance between two large masses, the gravitational force between them
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weakens by a factor of 4
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According to the universal law of gravitation, if you double the masses of both attracting objects, then the gravitational force between them will
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increase by a factor of 4
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An atom in an excited state contains more of what type of energy than the same atom in the ground state?
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electric potential energy
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The wavelength of a wave is
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The distance between two adjacent peaks of the wave
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How are wavelength, frequency, and energy related for photons of light?
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Longer wavelength means lower frequency and lower energy
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From lowest energy to highest energy, which of the following correctly orders the different categories of electromagnetic radiation?
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radio, infrared, visible light, ultraviolet, X rays, gamma rays
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When an electron in an atom goes from a higher energy state to a lower energy state, the atom
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emits a photon of a specific frequency
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The spectra of most galaxies show redshifts. This means that their spectral lines
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have wavelengths that are longer than normal
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From laboratory measurements, we know that a particular spectral line formed by hydrogen appears at a wavelength of 121.6 nanometers (nm). The spectrum of a particular star shows the same hydrogen line appearing at a wavelength of 121.8 nm. What can we conclude?
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The star is moving away from us.
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How does the Sun's mass compare with that of the planets?
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It is a thousand times more massive than all the planets combined.
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Which planet has the highest average surface temperature, and why?
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Venus, because of its dense carbon dioxide atmosphere
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Which planet, other than Earth, has visible water ice on it?
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Mars
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Which of the following is furthest from the Sun?
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a comet in the Oort cloud
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Which is the densest planet in the solar system?
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Earth
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The planet closest in size to Earth is
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Venus
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Which of the following is not a characteristic of the inner planets?
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They all have substantial atmospheres.
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Which of the following is not a characteristic of the outer planets?
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They have very few, if any, satellites.
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Why did the solar nebula heat up as it collapsed?
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As the cloud shrank, its gravitational potential energy was converted to kinetic energy and then into thermal energy
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What kind of material in the solar nebula could remain solid at temperatures as high as 1,500 K, such as existed in the inner regions of the nebula?
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metals
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What was the frost line of the solar system?
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the distance from the Sun where temperatures were low enough for hydrogen compounds to condense into ices, between the present-day orbits of Mars and Jupiter
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According to the nebular theory, what are asteroids and comets?
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They are leftover planetesimals that never accreted into planets
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Most of the planets discovered around other stars
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are more massive than Earth and orbit very close to the star
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Rank the five terrestrial worlds in order of size from smallest to largest:
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Moon, Mercury, Mars, Venus, Earth.
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Which of the following most likely explains why Venus does not have a strong magnetic field?
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Its rotation is too slow
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Which two properties are most important in determining the surface temperature of a planet?
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distance from the Sun and atmosphere
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How large is an impact crater compared to the size of the impactor?
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10 times larger
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The relatively few craters that we see within the lunar maria
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were formed by impacts that occurred after those that formed most of the craters in the lunar highlands.
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The Caloris Basin on Mercury covers a large region of the planet, but few smaller craters have formed on top of it. From this we conclude that
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the Caloris Basin formed toward the end of the solar system's period of heavy bombardment
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Olympus Mons is a
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shield volcano on Mars.
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Why does Venus have such a great difference in temperature between its "no atmosphere" temperature an its actual temperature?
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It has a large amount of greenhouse gases in its atmosphere.
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Which of the following worlds has the most substantial atmosphere?
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Venus
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Why doesn't Venus have seasons like Mars and Earth do?
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Its rotation axis is not tilted.
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Where is most of the water on Mars?
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in its polar caps and subsurface ground ice
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How does Jupiter's core compare to Earth's?
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It is about the same size but is 10 times more massive.
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if we know the size of an asteroid, we can determine its density by
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determining its mass from its gravitation pull on a spacecraft, satellite, or planet.
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What is Jupiter's Great Red Spot?
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a long-lived, high-pressure storm
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The four Galilean moons around Jupiter are
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a mixture of rock and ice, with the ice fraction increasing with distance from Jupiter
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Why are there no impact craters on the surface of Io?
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Io did have impact craters but they have all been buried in lava flows.
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Which moon has the most substantial atmosphere?
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Titan
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How thick are Saturn's rings from top to bottom?
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a few tens of meters
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Which is closest to the average distance between asteroids in the asteroid belt?
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1 million km
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Why isn't there a planet where the asteroid belt is located?
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Gravitational tugs from Jupiter prevented material from collecting together to a form a planet.
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Halley's comet is named after the English scientist Edmund Halley because he
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calculated its orbit and predicted that it would return in 1758
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What part of a comet points most directly away from the Sun?
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the plasma tail
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The core of the Sun is
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hotter and denser than the surface.
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What two forces are balanced in what we call gravitational equilibrium?
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outward pressure and gravity
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What is the average temperature of the surface of the Sun?
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6,000K
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Which layer of the Sun do we normally see?
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photosphere
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At the center of the Sun, fusion converts hydrogen into
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helium, energy, and neutrinos
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What is granulation in the Sun?
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the bubbling pattern on the photosphere produced by the underlying convection
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Approximately, what basic composition are all stars born with?
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three-quarters hydrogen, one-quarter helium, no more than 2 percent heavier elements
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Since all stars begin their lives with the same basic composition, what characteristic most determines how they will differ?
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mass they are formed with
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A star's luminosity is the
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total amount of light that the star radiates each second
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suppose that you measure the parallax angle for a particular star to be 0.5 arcsecond. The distance to this star is
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2 parsecs
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The spectral sequence in order of decreasing temperature is
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OBAFGKM
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Which of the following best describes the axes of a Hertzsprung-Russell (H-R) diagram?
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surface temperature on the horizontal axis and luminosity on the vertical axis
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What is the smallest mass a newborn star can have?
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80 times the mass of Jupiter
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What happens when a star exhausts its core hydrogen supply?
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Its core contracts, but its outer layers expand and the star becomes bigger and brighter.
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Compared to the star it evolved from, a red giant is
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cooler and brighter
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What is a planetary nebula?
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the expanding shell of gas that is no longer gravitationally held to the remnant of a low-mass star
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Which of the following sequences correctly describes the stages of life for a low-mass star?
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protostar, main-sequence, red giant, white dwarf
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After a supernova event, what is left behind?
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either a neutron star or a black hole
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White dwarfs are so called because
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they are both very hot and very small
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How does a 1.2-solar-mass white dwarf compare to a 1.0-solar-mass white dwarf?
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It has a smaller radius.
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Which of the following is closest in size (radius) to a white dwarf?
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Earth
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Which of the following is closest in size (radius) to a neutron star?
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a city
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From a theoretical standpoint, what is a pulsar?
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a rapidly rotation neutron star
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What is the basic definition of a black hole?
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any object from which the escape velocity exceeds the speed of light
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Which of the following statements about black holes is not true?
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If the sun magically disappeared and was replaced by a black hole of the same mass, Earth would soon be sucked into a black hole
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If you were to come back to our Solar System in 6 billion years, what might you expect to find?
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a white dwarf
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what is the diameter of the disk of the Milky Way?
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100,000 light-years
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Which of the following comprise the oldest members of the Milky Way?
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globular clusters
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Approximately how long does it take the Sun to orbit the Milky Way Galaxy?
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230 million years
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Which constellation lies in the direction toward the galactic center?
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Sagittarius
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Compared to spiral galaxies, elliptical galaxies are
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redder and rounder
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The disk component of a spiral galaxy includes which of the following parts?
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spiral arms
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Why are Cepheid variables important?
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Cepheids are pulsating variable stars, and their pulsation periods are directly related to their true luminosities.
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What is Hubble's law?
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The recession velocity of a galaxy is directly proportional to its distance from us
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Based on current estimates of the value of Hubble's constant, how old is the universe?
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between 12 and 16 billion years old
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I observe a galaxy that is 100 million light-years away: what do I see?
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the light from the galaxy as it was 100 million years ago and it is redshifted
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Why should galaxy collisions have been more common in the past than they are today?
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Galaxies were closer together in the past because the universe was smaller.
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What is a quasar?
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the extremely bright center of a distant galaxy, thought to be powered by a massive black hole
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What is meant by "dark energy"
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the agent causing the universal expansion to accelerate
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What is the evidence for an accelerating universe?
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White-dwarf supernovae are slightly dimmer than expected for a coasting universe
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To date, physicists have investigated the behavior of matter and energy at temperatures as high as those that existed in the universe as far as ___ after the Big Bang.
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10^-10 seconds
