CH.2 Mastering Astronomy

About how many stars are visible to the naked eye on a clear, dark night away from city lights? a few hundred billion a few dozen several million a couple thousand

What do astronomers mean by a constellation? A constellation is a group of stars that are all located in about the same place in space. A constellation is a region in the sky as seen from Earth. A constellation is any random grouping of stars in the sky. A constellation is a group of stars related through an ancient story.

What is the ecliptic? The Sun's daily path from east to west in our sky A half-circle extending from your horizon due north, through your zenith, to your horizon due south The path the Sun appears to trace around the celestial sphere each year The path traced by the Moon's shadow on Earth during a solar eclipse

What is the celestial sphere? The celestial sphere is a model of how the stars are arranged in the sky relative to our Sun, which is in the middle of the sphere. The celestial sphere is a model that shows the true locations in space of the Sun and a few thousand of the nearest stars. It represents a belief in an Earth-centered universe, and hence is no longer considered to have any use. The celestial sphere is a representation of how the entire sky looks as seen from Earth.

What do we mean when we talk about the Milky Way in our sky? The spiral-shaped galaxy in which we live. The whitish patch of light we see when we look toward the center of the Milky Way Galaxy. The patchy band of light that outlines the plane of the Milky Way Galaxy as seen from Earth. The bright stars of the constellations that lie along the ecliptic in our sky.

Which of the following statements does not use the term angular size or angular distance correctly? The angular size of the Sun is about the same as that of the Moon. You can use your outstretched hand against the sky to estimate angular sizes and angular distances. The angular distance between those two bright stars in the sky is about 2 meters. The angular distance between those two houses in the distance is 30 degrees.

Which of the following correctly describes the meridian in your local sky? The point directly over your head A half-circle extending from your horizon due east, through the north celestial pole, to your horizon due west A half-circle extending from your horizon due east, through your zenith, to your horizon due west A half-circle extending from your horizon due north, through your zenith, to your horizon due south

The point directly over your head is called _________. the north celestial pole the meridian the North Star the zenith

Stars that are visible in the local sky on any clear night of the year, at any time of the night, are called _________. celestial circumpolar seasonal bright

We describe a location on Earth's surface by stating its _________. altitude and direction (or azimuth) latitude and longitude latitude and direction meridian and longitude

If you are located in the Northern Hemisphere, which of the following correctly describes a relationship between the sky and your location? The altitude of the north celestial pole equals your longitude. The longitude of the north celestial pole is circumpolar, and therefore crosses your zenith at the meridian. The altitude of the north celestial pole equals your latitude. The altitude of the celestial equator equals your latitude.

Which of the following best describes why we have seasons on Earth? The tilt of Earth's axis causes different portions of the Earth to receive more or less direct sunlight at different times of year. The varying speed of Earth in its orbit around the Sun gives us summer when we are moving fastest and winter when we are moving slowest. Earth's elliptical orbit means we are closer to the Sun and therefore receive more intense sunlight at some times of year than at others. The tilt of Earth's axis causes the Northern Hemisphere to be closer to the Sun than the Southern Hemisphere in summer, and visa versa in winter.

Each choice describes how a few astronomical phenomena are related to time periods. Which list is entirely correct? (Careful: some lists are partially correct.) Earth's rotation defines a day. The cycle of the Moon's phases takes about a week. Earth's orbit defines a year. Earth's cycle of axis precession defines a month. Earth's rotation defines a day. The saros cycle of eclipses defines a month. Earth's orbit defines a year. Earth's cycle of axis precession takes 26,000 years. Earth's rotation defines a day. The cycle of the Moon's phases takes about a month. Earth's orbit defines a year. Earth's cycle of axis precession takes 26,000 years. Earth's rotation defines a day. The Sun's rotation defines a week. The Moon's rotation defines a month. Earth's orbit defines a year.

If we have a new moon today, when we will have the next full moon? In about two weeks In about a month In about one week In about six months

We cannot see a new moon in our sky because _________. a new moon is quite near the Sun in the sky it is above the horizon during the daytime no sunlight is illuminating the Moon it is obscured by Earth's shadow

The Moon always shows nearly the same face to Earth because ________. sunlight always hits the same face of the Moon the Moon does not rotate the Moon rotates once in the same amount of time that it takes Earth to orbit the Sun once the Moon rotates once in the same amount of time that it takes the Moon to orbit Earth once

Lunar eclipses can occur only during a _________. full moon new moon third-quarter moon first-quarter moon

What is the saros cycle? The roughly one-month cycle of lunar phases in the sky The 26,000-year cycle of the Earth's precession The roughly 18-year cycle over which the pattern of eclipses repeats The annual cycle of the seasons

During the time that a planet is in its period of apparent retrograde motion: _________ The planet is getting closer to the Sun in its orbit. The planet appears to rise in the west and set in the east, rather than the usual rising in the east and setting in the west. Over many days or weeks, the planet moves westward relative to the stars, rather than the usual eastward relative to the stars The planet moves backwards (clockwise as viewed from above Earth's north pole) in its orbit of the Sun.

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. It is the change in the set of constellations that we see at different times of year in the evening sky. It describes the fact that stars are actually moving relative to one another, even though to our eyes the stars appear fixed in the constellations. It is the daily rise and set of the stars.

Which of the following statements about the celestial sphere is not true? When we look in the sky, the stars all appear to be located on the celestial sphere. The Earth is placed at the center of the celestial sphere. The celestial sphere does not exist physically. The celestial sphere is another name for our universe.

The Andromeda Galaxy is faintly visible to the naked eye in the constellation Andromeda. Suppose instead it were located in the same direction in space as the center of the Milky Way Galaxy (but still at its current distance). How would it appear to the eye in that case? It would look about the same, but it would be harder to pick out because its cloud-like appearance would make it blend in with the cloud-like appearance of the Milky Way in our sky. It would be much brighter because it would be illuminated by the many stars in the center of our galaxy. We could not see it at all. It would look about the same but would be in the constellation Sagittarius instead of Andromeda.

An angle of 1 arcsecond is _________. slightly more than the width of a basketball held at arm's length about the width of a finger held at arm's length about the width of your fist held at arm's length less than the thickness of a human hair held at arm's length

When traveling north from the United States into Canada, you'll see the North Star (Polaris) getting _________. dimmer brighter lower in the sky higher in the sky

Suppose you use the Southern Cross to determine that the south celestial pole appears 40 degrees above your horizon. Then you must be located at _________. latitude 40 degrees south longitude 40 degrees latitude 40 degrees north latitude 50 degrees south

Suppose you are facing north and you see the Big Dipper close to your northern horizon, with Polaris (and the Little Dipper) above it. Where will you see the Big Dipper in six hours? To the right of Polaris; that is, 90 degrees counterclockwise from its current position To the left of Polaris; that is, 90 degrees clockwise from its current position Still in the same place, below Polaris Directly above Polaris

In any particular place on Earth, certain constellations are visible in the evening only at certain times of the year because _________. during some times of year, some constellations drop below the southern horizon some constellations are circumpolar our evening view of space depends on where Earth is located in its orbit around the Sun on any particular night, we can only see stars that are directly opposite (180 degrees away from) the Sun in the sky

The Sun's path, as viewed from the equator, is highest in the sky on _________. the day when Earth is closest to the Sun the December solstice the March and September equinoxes the June solstice

Suppose Earth's axis tilt was significantly greater than its current 23.5 degrees, but Earth's rotation period and orbital period were unchanged. Which statement below would not be true? The region of Earth where the Sun does not rise on the winter solstice would be larger (extending farther south) than it is now. The length of each season (for example, the number of days from the summer solstice to the fall equinox) would be significantly longer than it is now. Summers and winters would be more severe (for example, hotter and colder, respectively) than they are now. Polaris would not be our North star.

If our year were twice as long (that is, if Earth took twice as many days to complete each orbit around the Sun), but Earth's rotation period and axis tilt were unchanged, then _________. the Earth would not have seasons stars would take twice as long to rise and set the four seasons would each be twice as long as they are now the cycle of precession would take 13,000 years instead of 26,000 years

How does Earth's varying distance from the Sun affect our seasons? It doesn't; Earth's orbital distance plays no significant role in the seasons. It causes the seasons to be more extreme than they would be if the Earth's distance from the Sun were always the same. It makes summer warmer in the Northern Hemisphere than in the Southern Hemisphere. It is responsible for the fact that the seasons are opposite in the Northern and Southern hemispheres.

Suppose you live in the United States and you see a crescent moon in your evening sky tonight. What will a friend in South America see tonight? Your friend will see a first-quarter moon. Your friend will also see a crescent moon. Your friend will see a gibbous moon. Your friend won't see the Moon tonight because it is up only in the morning.

Suppose it is full Moon. What phase of Earth would someone on the Moon see at this time? full Earth Earth does not go through phases as seen from the Moon. new Earth first-quarter Earth

It's 6 a.m. and the Moon is at its highest point in your sky (crossing the meridian). What is the Moon's phase? first quarter third quarter new full

You observe a full Moon rising at sunset. What will you see at midnight? A full moon high in the sky A third-quarter moon A waning gibbous moon A first-quarter moon

All the following statements are true. Which one explains the reason that there is not a solar eclipse at every new moon? The nodes of the moon's orbit precess with an 18-year period. The Moon is only about one fourth as large as Earth in diameter. The orbital plane of the Moon is tilted slightly (by about 5 degrees) to the ecliptic plane. The Moon goes through a complete cycle of phases about every 29 1/2 days.

For most of history, the lack of observable stellar parallax was interpreted to mean that _________. Earth is stationary at the center of the universe stars must all lie at the same distance from Earth, on the celestial sphere Galileo's theories of the universe were essentially correct stars were too far away for parallax to be measured with available technology

During the period each year when we see Mars undergoing apparent retrograde motion in our sky, what is really going on in space? Earth is catching up with and passing by Mars in their respective orbits. Mars is moving around the Sun in the opposite direction from which Earth is moving around the Sun. Earth and Mars are getting closer together. Earth and Mars are on opposite sides of the Sun.

Suppose you see a photo showing Jupiter half in sunlight and half in shadow (that is, a first-quarter Jupiter). This photo might have been taken by _________. the Hubble Space Telescope (which orbits Earth) the Keck telescope on Mauna Kea, Hawaii the Galileo spacecraft that orbited Jupiter in the 1990s the Arecibo radio telescope in Puerto Rico