Astronomy Final Exam Practice – Flashcards
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If you are in the Earth's umbra, then...
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it is night time.
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The primary purpose of a telescope is to...
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collect a large amount of light and bring it into focus.
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The speed of light in a vacuum is...
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300,000 km/sec
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It is diffraction that limits _____ of a telescope of a given objective diameter.
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resolution
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What is the light-gathering power of an 8 inch telescope compared to a 4 inch telescope?
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4x better.
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One advantage of the Hubble Space telescope over ground based ones is that...
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in orbit, it can operate close to its diffraction limit at visible wavelengths.
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What is the resolution of a telescope?
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its ability to distinguish two adjacent objects close together in the sky.
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If the distance between two asteroids is doubled, the gravitational force they exert on each other will...
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be one fourth as great.
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In an annular eclipse...
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the Sun appears as a thin, bright ring.
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In general, what is true of the alpha star in a constellation?
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It is the brightest star in the constellation.
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The synodic month is...
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about 29.5 days.
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A solar eclipse can only happen during a...
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new moon.
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The fact that the Earth has moved along its orbit in the time it took to rotate once is the reason for...
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the difference between solar and sidereal time.
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How much stronger is the gravitational pull of the Sun on Earth, at 1 AU, than it is on Saturn at 10 AU?
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100
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In Ptolemy's geocentric model, retrograde motion occurs when the planet is closest to us, on the inside portion of the...
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epicycle.
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Compared to optical telescopes, radio telescopes are built large because...
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radio photons don't carry much energy.
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What problem does adaptive optics correct?
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Turbulence in Earth's atmosphere that creates twinkling.
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Tycho Brahe's contribution to Kepler's Laws of Planetary Motion were...
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His detailed and accurate observations of the planet's position.
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Which type of telescope did Galileo turn skyward in 1610?
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single lens refractor
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Which of these was NOT seen telescopically by Galileo?
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stellar parallax
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If the Moon appears half lit, and is almost overhead at about 6:00 AM, its phase is...
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third quarter.
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What are constellations?
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Groups of stars making an apparent pattern in the celestial sphere.
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What problem do refractor telescopes have that reflectors don't?
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chromatic aberration
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The greatest distance above or below the ecliptic the Moon can move is...
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5.2 degrees.
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A planet whose distance from the Sun is 3 AU would have an orbital period of how many Earth years?
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Square root of 27.
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Into how many constellations is the celestial sphere divided?
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88
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What is the name of the temperature scale that places zero at the point where all atomic and molecular motion ceases?
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Kelvin
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The interval from new Moon to first quarter is about a(n)...
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week
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Kepler's first law worked, where Copernicus' original heliocentric model failed, because Kepler described the orbits as...
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elliptical, not circular
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When the Moon is directly opposite the Sun in the sky, its phase is...
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full
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A fatal flaw with Ptolemy's model is its inability to predict the observed phases of...
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Mercury and Venus.
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The design of modern X-Ray telescopes depends on...
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grazing incidence optics
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The time for the Moon to orbit Earth, relative to the stars is...
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27.3 days
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A comet is in a highly elliptical orbit about the Sun. The speed of the comet is slowest when it is...
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farthest from the Sun.
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Consider two planets. The one with the longest period about the Sun is the...
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greatest distance from the Sun.
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Who hypothesized that the orbits of planets are ellipses, not circles?
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Kepler
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When a planet's orbit takes it closest to the Sun, it's called...
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perihelion.
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Why were epicycles used in Ptolemy's model of the solar system?
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To explain the retrograde motions of planets.
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Which of the following is a reason that the ancient Greek astronomers rejected the heliocentric model of the solar system?
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they could detect no stellar parallax
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Retrograde motion of a planet is...
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when, as viewed from Earth, a planet briefly appears to reverse direction and move east to west against a background of stars.
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During retrograde motion a planet appears to be...
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brighter than usual.
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The most important contribution of Tycho Brahe to astronomy was...
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to improve the accuracy of measurements of the location of objects.
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The main premise of Heliocentric theories is that...
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the Sun is at rest at the center of the universe and all heavenly bodies revolve.
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According to the heliocentric model, the retrograde motion for Mars must occur...
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at opposition, when the Earth overtakes Mars and passes between Mars and the Sun.
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What was the significance of Galileo's discovery that Venus shows all phases from new to full?
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In the geocentric model, only some phases are possible.
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Which scientists played a major role in overturning the ancient idea of an Earth-centered universe, and about when?
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Copernicus, Kepler, and Galileo; about 400 years ago.
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From Earth, the Sun and Moon have about the same angular diameter.
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True.
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The point directly over an observer's head is that observer's...
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zenith.
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The Earth's rotational axis if extended into space would appear to intersect the celestial sphere where?
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The celestial poles.
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Circumpolar stars are stars that...
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that never set in their daily motion about the celestial pole.
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What is an astronomical unit?
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The average distance from Earth to the Sun.
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A shift in the direction of an object caused by a change in the position of an observer is called...
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parallax.
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The occurrence of seasons on the Earth is due to...
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the Earth's axis being inclined to the ecliptic.
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The synodic period of a planet is...
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the time required for a planet to return to a particular configuration.
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The Earth's rotation about its axis has a...
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synodic period of approximately 24 hrs and a sidereal period of about 23 hrs 56 min.
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The age of the universe is...
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between 10 billion and 16 billion years.
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The Milky Way galaxy takes _____ years to complete one rotation.
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200 million years
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The Milky Way Galaxy contains about...
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100 billion stars.
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In the Hubble Ultra Deep Field Image, the bluest objects are among the furthest objects ever detected.
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False.
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What is true of the Moon's orbital and rotational periods?
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They are equal.
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When Saturn is at Equinox, its rings will...
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lie in the plane of the ecliptic.
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The Kuiper Belt is found where in the solar system?
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Beyond the orbit of Neptune.
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Our most detailed knowledge of Uranus and Neptune comes from...
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spacecraft exploration
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The Moon's near side always faces Earth due to...
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Earth's tidal force.
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Which statement is true of Venus' surface?
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There are two continent sized uplands.
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Pluto was discovered in...
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1930.
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The atmospheric pressure on Venus...
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is much higher than on Earth.
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The largest moon in the solar system, bigger but not as massive as Mercury, is...
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Ganymede.
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Which element is critical to the formation of the volcanic surface of Io?
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sulfur
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Which of these gases is least abundant in our atmosphere?
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hydrogen
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Which of the following characterizes a shield volcano?
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It cannot get as high as Mt. Everest before the thin crust starts slumping.
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Essentially, the Great Red Spot is...
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a large cyclonic storm (hurricane).
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We determine the structure of the Earth's core using...
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seismic wave data.
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The spacecraft Cassini went into orbit around...
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Saturn.
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Which of these gets so bright as to be seen in daylight at times?
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Venus.
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The two outer jovians appear bluish in color because...
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methane gas in their atmospheres absorbs red light well.
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Small deviations in a planet's orbital motion...
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imply the nearby presence of a massive body
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Valles Marineris is the most striking example of a(n)...
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rift valley.
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The smallest high tides occur when the Moon phase is...
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first or third quarter.
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Which body has the densest atmosphere?
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Venus.
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What is the source of Jupiter's intense radio waves and magnetism?
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liquid metallic hydrogen swirling in the rapidly spinning mantle
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The largest asteroid, and probably the only one to be spherical, is...
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Ceres
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So far, beyond the solar system the extrasolar planets found have been mostly...
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large jovians with terrestrial-type orbits.
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Which of these is not a result of plate tectonics?
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The Grand Canyon.
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Which of the following is not icy in composition?
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asteroids
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Earth's magnetic field...
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prevents charged particles in the solar wind from reaching the surface.
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A meteor is...
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an irregularly shaped body, mostly found orbiting between Mars and Jupiter.
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What is true of Mars?
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Iron oxide on the surface is responsible for its reddish color.
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Which Jovian moon shows the most diverse terrain, suggesting a violent impact broke it into many pieces, some of which reformed as a jumbled puzzle?
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Miranda
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The reason the jovian planets lost very little of their original atmosphere is due to their...
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large mass.
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A moon with a smooth, uncratered surface would imply...
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the surface is very young.
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Iron meteorites are believed to come from...
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the core of a differentiated asteroid, now broken up.
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The scarps on Mercury were probably caused by...
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the crust cooling and shrinking.
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Mercury's surface most resembles which of these?
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our Moon's far side.
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The nucleus of a comet is typically...
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a few meters in diameter.
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The presence of Earth's magnetic field is a good indication that...
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we have a liquid metal outer core, spinning rapidly as we rotate.
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The jovian planets...
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all have rings around their equators.
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Which of these moons has the densest atmosphere?
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Titan
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The most distant objects in our solar system are...
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in the Oort Cloud.
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Which of the following have an icy composition?
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Comets.
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In terms of axial tilt, which of the jovians shows us the largest inclination?
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Uranus
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Planetary orbits...
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are almost circular, with low eccentricities.
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As a rotating gas cloud contracts, it spins...
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faster due to conservation of angular momentum.
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The atmospheric gas most responsible for Earth's greenhouse effect is...
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water vapor.
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The lunar mare are found...
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mainly on the near side.
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What statistic below has changed the most in the last decade?
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the number of extra-solar planets.
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What is the main constituent of the atmosphere of Venus?
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carbon dioxide
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The tail of a comet always points...
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away from the Sun and becomes longest and brightest at perihelion.
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The Oort Cloud is believed to be...
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a spherical cloud of cometary nuclei far beyond the Kuiper Belt.
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Which of the following are the jovian planets?
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Jupiter, Saturn, Uranus, and Neptune only
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The orbits of most comets...
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lie almost entirely beyond the orbit of Neptune.
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In terms of composition...
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the jovian planets are more like the Sun than are the terrestrials.
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In size and density, both Io and Europa resemble...
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our Moon.
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Which planet by itself contains the majority mass of all the planets?
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Jupiter
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Why are the rings of Saturn so bright?
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They are made of young, fresh water ice.
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What would Jupiter have needed to be a star?
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Enough more mass to make the planet hotter.
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Venus' rotation on its axis...
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is retrograde, unlike most other solar system objects.
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The most detailed look we've had of an asteroid comes from...
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spacecraft sent to an asteroid.
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The far side of the moon was first mapped...
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by early Russian spacecraft.
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How much brighter will a 4th magnitude star appear than a 6th magnitude star?
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6.25x
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Why are star clusters ideal "laboratories" for stellar evolution?
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Their stars are all about the same age, composition, and distance from us.
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The single most important determinant of the temperature, density, radius, luminosity, and pace of evolution of a protostar is its...
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mass.
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A white dwarf has the mass of the Sun and the volume of...
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Earth.
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On the H-R diagram, red supergiants like Betelgeuse lie...
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at the top right.
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A star is on the horizontal branch of the H-R diagram. Which statement is true?
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It is burning both hydrogen and helium.
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Sunspots...
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come in pairs, representing the north and south magnetic fields
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If we know the average separation and period of revolution for a binary system, we can then measure...
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...
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What can you conclude about a Type I supernova?
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it was originally a low mass star.
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Which of these evolutionary paths is the fate of our Sun?
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planetary nebula
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The Doppler shift is used to find...
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Spectroscopic binaries
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In what range of masses are most stars found?
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...
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If it gains sufficient mass, a white dwarf can become a...
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Type I supernova.
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While observing the Sun, you note a large number of sunspots. What can you conclude?
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There are likely to be an above average number of flares and prominences.
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Of the elements in your body, the only one not formed in stars is...
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hydrogen.
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How long does the sunspot cycle last, on average?
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about 11 years
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A hypernova creates...
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short-duration gamma-ray bursts.
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What two things are needed to create an emission nebulae?
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hot stars and interstellar gas, particulary hydrogen
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The most striking example of solar variability was the...
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Maunder Minimum from 1645-1715.
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Type II supernovae occur when their cores start making...
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iron.
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Which of these are not associated with the active Sun?
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granulation
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On an H-R diagram, a protostar would be...
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above and to the right of the main sequence.
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If light from a distant star passes close to a massive body, the light beam will...
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bend towards the star due to gravity.
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What temperature is needed to fuse helium into carbon?
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100 million K
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An iron core cannot support a star because...
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iron cannot fuse with other nuclei to produce energy.
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What made supernova 1987A so useful to study?
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Its progenitor had been observed previously; In the Large Magellanic Cloud, we already knew its distance; It occurred after new telescopes, such as Hubble, could observe it very closely; We saw direct evidence of nickel to iron decay in its light curve.
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The total energy radiated by a blackbody depends on...
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the fourth power of its temperature.
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On the H-R diagram, the Sun lies...
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about the middle of the main sequence.
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The heaviest nuclei of all are formed...
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in the core collapse which sets the stage for a type II supernova
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Which statement about black holes is true?
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Their escape velocity is greater than the speed of light.
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A star is 10 parsecs from Earth. Which statement is true?
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The star is about 33 ly away.
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An object more massive than the Sun, but roughly the size of a city, is a...
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neutron star.
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From inside out, which is in the correct order for the structure of the Sun?
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radiative zone, convective zone, chromosphere
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In a neutron star, the core is...
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made of compressed neutrons in contact with each other.
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If Vega is apparent magnitude zero, and Deneb first magnitude, then...
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Vega is 2.5X brighter than Deneb.
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If the Sun were replaced by a one-solar-mass black hole,...
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we would still orbit it in a period of one year.
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The observed spectral lines of a star are all shifted towards the red end of the spectrum. Which statement is true?
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This is an example of the Doppler effect.
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The radiation our eyes are most sensitive to lies in the color...
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yellow-green at about 550 nm.
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In the proton-proton cycle, the helium atom and neutrino have less mass than the original hydrogen. What happens to the "lost" mass?
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It is converted to energy
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The critical temperature to initiate the proton-proton cycle in the cores of stars is...
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10 million K.
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The H-R diagram plots...
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temperature versus luminosity.
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A star (no matter what its mass) spends most of its life...
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as a main-sequence star.
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Which of these stars would be the hottest?
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B0
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The outward pressure of hot gas in the Sun...
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is balanced by the inward gravitational pressure.
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The density of the Sun is most similar to which object?
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Jupiter
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When a star's inward gravity and outward pressure are balanced, the star is said to be...
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Hydrostatic equilibrium
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What explanation does general relativity provide for gravity?
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Gravity is the result of curved spacetime.
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What can be said with certainty about a red star and a blue star?
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The blue star is hotter than the red star.
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In Bohr's model of the atom, electrons...
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only make transitions between orbitals of specific energies
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The temperature of the Sun's photosphere is about...
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5,800 K.
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What is true of a blackbody?
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Its energy peaks at the wavelength determined by its temperature.
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What happens to light passing through even thin clouds of dust?
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It dims and reddens the light of all more distant stars.
