Ast 103 Study Guide

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How long does it take our solar system to complete one orbit around the Milky Way Galaxy?
230 million years
Which scientists played a major role in overturning the ancient idea of an Earth-centered universe, and about when?
Copernicus, Kepler, and Galileo; about 400 years ago
Earth is made mostly of metals and rocks. Where did this material come from?
It was produced by nuclear fusion in stars.
What is the ecliptic?
the Sun's apparent path along the celestial sphere
Momentum is defined as
mass times velocity.
Kepler's third law, p2 = a3, means that

a planet's period does not depend on the eccentricity of its orbit. ; all orbits with the same semimajor axis have the same period. ; the period of a planet does not depend on its mass. ; planets that are farther from the Sun move at slower average speeds than nearer planets. (all of the above)

Why do we have seasons on Earth?
As Earth goes around the Sun and Earth's axis remains pointed toward Polaris, the Northern and Southern hemispheres alternately receive more and less direct sunlight.
When are eclipse seasons?
when the nodes of the Moon's orbit are nearly aligned with the Sun
According to the universal law of gravitation, the force due to gravity is
inversely proportional to the square of the distance between objects.
According to the universal law of gravitation, if you double the masses of both attracting objects, then the gravitational force between them will
increase by a factor of 4.
The names of the seven days of the week are based on the
seven naked-eye objects that appear to move among the constellations.
Which of the following statements about scientific models is true?
A model can be used to explain and predict real phenomena.
Considering Einstein's famous equation, E = mc2, which of the following statements is true?
A small amount of mass can be turned into a large amount of energy.
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 Earth.
Kepler's second law, which states that as a planet moves around its orbit it sweeps out equal areas in equal times, means that
a planet travels faster when it is nearer to the Sun and slower when it is farther from the Sun.
What do scientists mean by verifiable observations?
observations that can be interpreted in only one way
Suppose an object is moving in a straight line at 50 miles/hr. According to Newton's first law of motion, the object will
continue to move in the same way until it is acted upon by a force.
Newton's second law of motion tells us that the net force applied to an object equals its
mass times acceleration.
Changing the orbit of a spacecraft by firing thrusters is an example of
Newton's third law of motion.
Which of the following best describes the origin of ocean tides on Earth?
Tides are caused by the difference in the force of gravity exerted by the Moon across the sphere of the earth.
Which of the following statements about circumpolar stars is true at all latitudes?
They always remain above your horizon.
What is stellar parallax?
It is the slight back-and-forth shifting of star positions that occurs as we view the stars from different positions in Earth's orbit of the Sun.
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.
From Kepler's third law, an asteroid with an orbital period of 8 years lies at an average distance from the Sun equal to
4 astronomical units.
In which of the following cases would you feel weightless?
while falling from a roof
What is meant by a hypothesis?
an explanation for a phenomenon that makes a prediction
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
weakens by a factor of 4.
The allowed shapes for orbits under the force of gravity are
ellipses, parabolas, and hyperbolas.
Roughly how many stars are in the Milky Way Galaxy
100 million
Approximately how fast are you moving with the rotation of Earth?
1,300 km/hr
"From shortest to longest wavelength, which of the following correctly orders the different categories of electromagnetic radiation?
gamma rays, X rays, ultraviolet, visible light, infrared, radio
When an atom absorbs a photon containing energy, any of the following can happen except which?
The atom is ionized.
Consider an atom of gold in which the nucleus contains 79 protons and 118 neutrons. What is its atomic number and atomic weight?
The atomic number is 79, and the atomic weight is 197.
How can an electron in an atom lose energy to go from a higher energy level to a lower energy level?
It releases a photon equal in energy to its own energy drop.
You observe a distant galaxy. You find that a spectral line normally found in the visible part of the spectrum is shifted toward the infrared. What do you conclude?
The galaxy is moving away from you.
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.
Which of the following could not be determined by an observation that uses only spectroscopy?
The size of a distant galaxy
How are wavelength, frequency, and energy related for photons of light?
Longer wavelength means lower frequency and lower energy.
What do astronomers mean by light pollution?
Light pollution refers to light used for human activities that brightens the sky and hinders astronomical observations.
What is meant by spectral resolution?
It is a measure of how close two spectral lines can be distinguished.
The planet closest in size to Earth is
According to our basic scenario of solar system formation, why do the jovian planets have numerous large moons?
Because of their strong gravity, the jovian planets were able to capture numerous asteroids that happened to be passing nearby, and these became the major moons of the jovian planets.
Which of the following statements about the asteroid belt is not true?
The combined mass of all the asteroids is roughly the same as the mass of Earth.
Venus has a higher average surface temperature than Mercury. Why?
because its surface is heated by an extreme greenhouse effect
In what way is Pluto more like a comet than a planet?
It is made mostly of rock and ice.
How is Einstein's famous equation, E= mc2 , important in understanding the Sun?
"It explains the fact that the Sun generates energy to shine by losing some 4 million tons of mass each day.
What percentage of the mass of the solar nebula consisted of elements other than hydrogen and helium?
2 percent
Why did the solar nebula heat up as it collapsed?
As the cloud shrank, its gravitational potential energy was converted to kinetic energy and then into thermal energy.
What was the frost line of the solar system?
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
According to our theory of solar system formation, why do we find some exceptions to the general rules and patterns of the planets?
Most of the exceptions are the result of giant impacts.
Which planet has the highest average surface temperature, and why?
Venus, because of its dense carbon dioxide atmosphere
What is the primary reason that astronomers suspect that some jovian moons were captured into their current orbits?
Some moons have orbits that are "backwards" (compared to their planet's rotation) or highly inclined to their planet's equator.
According to our present theory of solar system formation, how did Earth end up with enough water to make oceans?
The water was brought to the forming Earth by planetesimals that accreted beyond the orbit of Mars.
The nebular theory of the formation of the solar system successfully predicts all but one of the following. Which one does the theory not predict?
the equal number of terrestrial and jovian planets
According to the nebular theory, how did the Kuiper belt form?
It is made of planetesimals that formed beyond Neptune's orbit and never accreted to form a planet.
What is the primary reason why a Pluto flyby mission would be cheaper than a Pluto orbiter?
The fuel needed for an orbiter to slow down when it reaches Pluto adds a lot of weight to the spacecraft.
Suppose you start with 1 kilogram of a radioactive substance that has a half-life of 10 years. Which of the following statements will be true after 20 years pass?
You'll have 0.25 kilogram of the radioactive substance remaining.
How does the Sun's mass compare with that of the planets?
It is a thousand times more massive than all the planets combined.
In what part of the electromagnetic spectrum do the biggest telescopes on Earth operate?
The spectra of most galaxies show redshifts. This means that their spectral lines
always are in the red part of the visible spectrum.
The lithosphere of a planet is the layer that consists of
the rigid rocky material of the crust and uppermost portion of the mantle.
Which internal energy source produces heat by converting gravitational potential energy into thermal energy?
both Accretion and Differentiation
Which internal energy source is the most important in continuing to heat the terrestrial planets today?
Which of the following show evidence of ancient river beds?
How does seafloor crust differ from continental crust?
Seafloor crust is thinner, younger, and higher in density.
How large is an impact crater compared to the size of the impactor?
10 times larger
The terrestrial planet cores contain mostly metal because
metals sank to the center during a time when the interiors were molten throughout.
How fast do plates move on Earth?
a few centimeters per year
The relatively few craters that we see within the lunar maria
were formed by impacts that occurred after those that formed most of the craters in the lunar highlands.
A planet is most likely to have tectonic activity if it has
high internal temperature.
Which of the following is not evidence for plate tectonics on Earth?
existence of volcanoes
Why does Venus have such a great difference in temperature between its "no atmosphere" temperature and its actual temperature?
It has a slow rotation.
Convection occurs in the troposphere but not in the stratosphere because
lower altitudes of the troposphere are warmer than higher altitudes, unlike in the stratosphere.
Why does the burning of fossil fuels increase the greenhouse effect on Earth?
Burning releases carbon dioxide into the atmosphere.
Earth has been gradually warming over the past few decades. Based on a great deal of evidence, scientists believe that this warming is caused by
human activities that are increasing the concentration of greenhouse gases in Earth's atmosphere.
How many more times is the atmospheric pressure in Jupiter's core greater than the atmospheric pressure at Earth's surface?
100 million
The Huygens probe took numerous pictures as it descended to Titan's surface in 2005. What did the pictures show?
features or erosion, including what appeared to be dry river valleys and lakebeds
According to our theory of solar system formation, why did Uranus and Neptune end up to be much less massive than Jupiter and Saturn?
Particles in the solar nebula were more spread out at greater distances, so that accretion took longer and there was less time to pull in gas before the solar wind cleared the nebula.
Which of the following best describes why we see horizontal "stripes" in photographs of Jupiter and Saturn?
The light stripes are regions of high clouds, and the dark stripes are regions where we can see down to deeper, darker clouds.
How does the greenhouse effect work?
Greenhouse gases absorb thermal radiation that is emitted by the surface.
How much of the mass of the moon system around Jupiter is in regular moons rather than irregular moons?
99.997% Percent
What is a regular satellite?
One that is in an inclined and eccentric orbit
What kind of surface features may result from tectonics?
mountains, valleys, cliffs (All of the above)
Which of the following best describes why the smaller terrestrial worlds have cooler interiors than the larger ones?
They have relatively more surface area compared to their volumes.
What drives the motion of the tectonic plates on Earth?
convection cells in the mantle
Why are there fewer large craters on the seafloor than on the continents?
The seafloor crust is younger than the continental crust.
Volcanism is more likely on a planet that
has high internal temperatures.
Which of the following describes impact cratering?
the excavation of bowl-shaped depressions by asteroids or comets striking a planet's surface
There are no aurora on Venus because it
lacks a strong magnetic field.
Which of the following best describes rain on Venus?
It has sulfuric acid rain in its atmosphere, but the drops evaporate before hitting the surface.