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Flashcards in Chapter 2 Deck (53):
1

Suppose that instead of being inclined to Earth's orbit around the Sun, the Moon’s orbit was in the same plane as Earth’s orbit around the Sun. In this hypothetical situation, approximately how many solar eclipses would occur each year?

12

2

In reality, the Moon’s orbit about Earth is tilted (by about 5°) with respect to Earth’s orbit about the Sun. As a result, the actual number of solar eclipses that occur each year is approximately _____.

2

3

What conditions must exist for a solar eclipse to occur?

The phase of the Moon must be new and the Moon must be passing through Earth’s orbital plane.

4

What conditions must exist for a lunar eclipse to occur?

The phase of the Moon must be full and the Moon must be passing through Earth’s orbital plane.

5

If you could change the layout of the solar system, which of the following would cause a lunar eclipse to occur at least once every month in this hypothetical situation?

Change the Moon’s orbital plane so it is in the same plane as Earth’s orbit around the Sun.

6

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

The "celestial sphere" is another name for our universe.

7

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.

8

An angle of 1 arcsecond is _________.

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

9

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

higher in the sky

10

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

11

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

12

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

13

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

the spring and fall equinoxes

14

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.
Polaris would not be our North star.
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.

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.

15

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

16

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.

17

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.

18

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

new Earth

19

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

20

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

A full moon high in the sky

21

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 goes through a complete cycle of phases about every 29 1/2 days.
The orbital plane of the Moon is tilted slightly (by about 5 degrees) to the ecliptic plane.
The Moon is only about 1/4 as large as Earth in diameter.

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

22

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

Earth is stationary at the center of the universe

23

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.

24

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

25

When it is summer in Australia, it is:

winter in the United States.

26

The North Celestial Pole is 35.0 above your northern horizon. This tells you that:

you are at latitude 35.0 N.

27

Beijing and Philadelphia have about the same latitude but very different longitudes. Therefore, tonight's night sky in these two places:

will look about the same.

28

In winter, Earth's axis points toward the star Polaris. In spring:

the axis also points toward Polaris.

29

Two stars that are in the same constellation:

may actually be very far away from each other.

30

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

A couple thousand

31

What do astronomers mean by a constellation?

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

32

What is the ecliptic?

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

33

What is the celestial sphere?

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

34

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.

35

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.
You can use your outstretched hand against the sky to estimate angular sizes and angular distances.
The angular size of the Sun is about the same as that of the Moon.
The angular distance between those two houses in the distance is 30 degrees

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

36

What describes the meridian in your local sky?

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

37

The point directly over your head is called _________.

the zenith

38

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

circumpolar

39

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

latitude and longitude

40

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.

41

why do 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.

42

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.

43

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

In about 2 weeks

44

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

a new moon is quite near the Sun in the sky

45

Lunar eclipses can occur only during a _________.

full moon

46

What is the saros cycle?

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

47

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

48

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.

49

If the Sun rises precisely due east:

it must be the day of either the spring or fall equinox.

50

A week after full moon, the Moon's phase is:

third quarter

51

Some type of lunar or solar eclipse (not necessarily a total eclipse) occurs

at least four times a year

52

If there is going to be a total lunar eclipse tonight, then you know that:

the Moon's phase is full

53

When we see Saturn going through a period of apparent retrograde motion, it means

Earth is passing Saturn in its orbit, with both planets on the same side of the Sun.