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56 Cards in this Set
- Front
- Back
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How are galaxies important to our existence? |
Galaxies recycle heavy elements produced in stars into future generations of stars. |
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Why is it summer in the Northern Hemisphere when it is winter in the Southern Hemisphere? |
The Northern Hemisphere is tilted toward the Sun and receives more direct sunlight. |
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Why were ancient peoples unable to detect stellar parallax? |
They did not have the ability to measure very small angles. |
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What is true about a scientific model? |
A model tries to represent all aspects of nature. |
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How did the Ptolemaic model explain the apparent retrograde motion of the planets? |
It held that the planets moved along small circles that moved on larger circles around the Earth. |
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Who discovered that Jupiter has moons? |
Galileo |
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From laboratory measurements, we know that a particular spectral line formed byhydrogen appears at a wavelength of 486.1 nanometers (nm). The spectrum of aparticular star has the same hydrogen line appearing at a wavelength of 485.9 nm.What can we conclude? |
The star is moving toward us. |
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Which planet has the highest average surface temperature, and why? |
Venus, because of its dense carbon dioxide atmosphere. |
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Which two properties are the most important in determining the surface temperature of a planet? |
Distance from the Sun and atmosphere. |
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How is the atmosphere of a planet affected by the rotation rate? |
Faster rotation rates produce stronger winds. |
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Suppose you put two protons near each other. Because of the electromagnetic force, the two protons will __________. |
repel each other. |
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Which two physical processes balance each other to create the condition known as gravitational equilibrium in stars? |
the gravitational force and outward pressure. |
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On a Hertzsprung-Russell diagram, where on the main sequence would we find stars that have the greatest mass? |
upper left |
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Our Sun is a star of spectral type _____. |
G |
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Sirius is a spectral type A star whereas Rigel is a spectral type B star. What can we conclude? |
Rigel has a higher surface temperature than Sirus. |
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What two properties of a Cepheid variable are directly related to one another? |
the period between its peaks of brightness and its distance |
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If we say that a galaxy has a lookback time of 1 billion years, we mean that ___________. |
its light travelled through space for 1 billion years to reach us |
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What do astronomers mean by the large-scale structure of the universe? |
the overall arrangement of galaxies, clusters of galaxies, and superclusters in the universe. |
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Space within clusters of galaxies is not expanding because ____________. |
their gravity is strong enough to hold them together even while the universe as a whole expands. |
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What happens when a particle of a matter meets its corresponding antiparticle of antimatter? |
The combined mass of the two particles is completely transformed into photons. |
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What does cosmological redshift do to light? |
stretches it in wavelength |
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What does the Schwarzchild radius of a black hole depend on? |
only the mass of the black hole |
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When we say that a cluster of galaxies is acting as a gravitational lens, what do we mean? |
It bends or distorts the light coming from galaxies located behind it. |
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The main source of energy for a star as it grows in size to become a red giant is __________. |
hydrogen fusion in a shell surrounding the central core. |
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The faintest star visible to the naked eye has an apparent visual magnitude of _______. |
+6 |
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We do not expect to find life on planets orbiting high-mass stars because ____________. |
their lifetimes are too short. |
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Suppose you drop a clock toward a black hole. As you look at the clock from a high orbit, what will you notice? |
Time on the clock will run slower as it approaches the black hold, and light from the clock will be increasingly redshifted. |
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In addition to the conditions required for any solar eclipse, what must also be true in order for you to observe a total solar eclipse? |
The Moon's umbra must touch the area where you are located. |
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Which phenomena causes the direction of the celestial poles to change from time to time? |
Precession of Earth's axis of rotation. |
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The dark regions of the Moon are known as ________. |
Maria |
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A light source emits only green light. Which statement given below is consistent with the fact that the source is moving towards a naked-eye observer? |
The observer perceives that the source emits only blue light. |
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How long would it take to count all the stars in the Milky Way Galaxy at a rate of one star per second? |
Several thousand years |
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Orion is visible on winter evenings but not summer evenings because of ____________. |
the location of the Earth in its orbit |
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What conditions are required for a lunar eclipse? |
The phase of the Moon must be full, and the nodes of the Moon's orbit must be nearly aligned with the Earth and the Sun. |
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Ptolemy was important in the history of astronomy because he _____________. |
developed a model of the solar system that made sufficiently accurate predictions of planetary positions to remain in use for many centuries. |
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When Copernicus first created his Sun-centered model of the universe, it did not lead to substantially better predictions of planetary positions than the Ptolemaic model. Why not? |
Copernicus used perfect circles for the orbits of the planets. |
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When a rock is held above the ground, we say it has some potential energy. When we finally let it go, it falls and we say the potential energy is converted to kinetic energy. Finally, the rock hits the ground. What has happened to the energy? |
The energy goes to producing sound and to heating the ground, rock, and surrounding air |
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The mass of Jupiter can be calculated by __________. |
measuring the orbital period and distance of one of Jupiter's moons. |
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Suppose the angular separation of two stars is smaller than the angular resolution of your eyes. How will the stars appear to your eyes? |
The two stars will look like a single point of light. |
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How do asteroids differ from comets? |
Asteroids are rocky bodies and are denser than comets, which are made if icy materials. |
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The habitable zone around a star is ___________. |
the region around a star where liquid water can exist on planetary surfaces. |
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What makes up the interstellar medium? |
Gas and dust |
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Where would we find stars that are cool and luminous on a Hertzsprung-Russell diagram? |
Upper right |
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Which two quantities of galaxies did Edwin Hubble compare to discover the expansion of the Universe? |
Velocity & distance |
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A white dwarf is supported by __________. |
Electron degeneracy pressure |
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Why does a star grow larger after it exhausts its core hydrogen? |
Hydrogen fusion in a shell outside the core generates enough thermal pressure to push the upper layers outward |
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What processes are involved in the sunspot cycle? |
the winding of magnetic field lines due to variations in the Sun's rotation |
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All the iron on Earth originated from _____. |
nuclear fusion within the cores of high-mass stars. |
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Compared to spiral galaxies, elliptical galaxies are __________. |
redder and rounder. |
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Current theories cannot describe what happened during the planck era because ___________. |
we do not yet have a theory that links quantum mechanics and general relativity. |
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A protostar becomes a main-sequence star when _______. |
the rate of hydrogen fusion within its core is high enough to sustain gravitational equilibrium. |
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The most accurate method to determine the distance to a nearby star is _______. |
Stellar parallax |
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Compared with stars in the disk, orbits if stars in the halo of a spiral galaxy |
are elliptical, with random orientation. |
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After a massive-star supernova, what is left behind? |
either a neutron star or black hole |
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A large mass-to-light ratio for a galaxy indicates that _________. |
on average, each solar mass of matter in the galaxy emits more light than our Sun. |
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In 1924, Edwin Hubble proved that the Andromeda Galaxy lay far beyond the bounds of the Milky Way, thus putting to rest the idea that it might have been a cloud within our own galaxy. How was he able to prove this? |
He observed individual Cepheid variable stars in Andromeda Galaxy and applied the period-luminosity relation. |
