AST 2003 Chapter 2

Which photo shows what we call a first quarter moon?

2

Which position in this diagram represents Earth on the day that we have the longest amount of daylight in the continental United States?

2

Which photo shows what we call a gibbous moon?

3

Which position in this diagram represents Earth at the beginning of spring for the Southern Hemisphere?

3

Part complete What do astronomers mean by a constellation?

A constellation is a region in the sky as seen from Earth

Part complete About how many stars are visible to the naked eye on a clear, dark night away from city lights?

A couple thousand.

You observe a full moon rising at sunset. What will you see at midnight?

A full moon high in the sky.

Part complete Which of the following correctly describes the meridian in your local sky?

A half-circle extending from your horizon due north, through your zenith, to your horizon due south.

What is this a picture of?

A total solar eclipse.

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.

For most of history, the lack of observable stellar parallax was interpreted to mean that _________.

Earth is stationary at the center of the universe

Each choice below 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 month. Earth's orbit defines a year. Earth's cycle of axis precession takes 26,000 years

If we have a new moon today, when we will have the next full moon?

In about 2 weeks.

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.

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.

What is the approximate latitude and longitude of the South American location marked by the black dot on this diagram?

Latitude = 15∘S, longitude = 45∘W.

Suppose it is full moon. What phase of Earth would someone on the Moon see at this time?

New Earth.

During the time that a planet is in its period of apparent retrograde motion: _________

Over many days or weeks, the planet moves westward relative to the stars, rather than the usual eastward relative to the stars.

Which of the following statements about the celestial sphere is NOT true?

The "celestial sphere" is another name for our universe

Part complete 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 latitude

Part complete Which of the following statements does not use the term angular size or angular distance correctly?

The angular distance between those two bright stars in the sky is about 2 meters.

Part complete What is the celestial sphere?

The celestial sphere is a representation of how the entire sky looks as seen from Earth.

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 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.

This diagram represents a person's local sky. What does the red semicircle represent?

The meridian.

All the following statements are true. Which one explains the reason that there is not a solar eclipse at every new moon?

The orbital plane of the Moon is tilted slightly (by about 5 degrees) to the ecliptic plane.

Part complete What do we mean when we talk about the Milky Way in our sky?

The patchy band of light that outlines the plane of the Milky Way Galaxy as seen from Earth.

Part complete What is the ecliptic?

The path the Sun appears to trace around the celestial sphere each year.

What is the saros cycle?

The roughly 18-year cycle over which the pattern of eclipses repeats

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.

It's 6 am and the Moon is at its highest point in your sky (crossing the meridian). What is the Moon's phase?

Third quarter.

Part complete 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

Part complete 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?

We could not see it at all.

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 also see a crescent moon.

We cannot see a new moon in our sky because _________.

a new moon is quite near the Sun in the sky

Diagrams like this one are commonly used in discussions of seasons and they can be quite useful. However, this diagram greatly exaggerates:

all of the above

Part complete Stars that are visible in the local sky on any clear night of the year, at any time of the night, are called _________.

circumpolar

Lunar eclipses can occur only during a _________.

full moon

When traveling north from the United States into Canada, you'll see the North Star (Polaris) getting _________.

higher in the sky

Part complete 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

We describe a location on Earth's surface by stating its _________.

latitude and longitude

An angle of 1 arcsecond is _________.

less than the thickness of a human hair held at arm's length

Part complete In any particular place on Earth, certain constellations are visible in the evening only at certain times of the year because _________.

our evening view of space depends on where Earth is located in its orbit around the Sun

This multiple exposure photograph shows the apparent retrograde motion of Mars. To make this picture, the photographer needed to combine individual photos of Mars taken over a period of:

several months.

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 Galileo spacecraft that orbited Jupiter in the 1990s

Part complete The Moon always shows nearly the same face to Earth because ________.

the Moon rotates once in the same amount of time that it takes the Moon to orbit Earth once

This diagram represents a simplified model of the celestial sphere. The unlabeled circle that is highlighted in purple represents:

the celestial equator.

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 four seasons would each be twice as long as they are now

The Sun's path, as viewed from the equator, is highest in the sky on _________.

the spring and fall equinoxes

Part complete The point directly over your head is called _________.

the zenith