Astronomy Quiz 2

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

A couple thousand

constellation

a region in the sky as seen from Earth.

ecliptic

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

celestial sphere

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

meridian

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

zenith

The point directly over your head

circumpolar

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

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

latitude and longitude

The altitude of the north celestial pole equals your ____________

latitude

Why do we have seasons?

The tilt of Earth's axis causes different portions of the Earth to receive more or less direct sunlight at different times of year.

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

2 weeks

We cannot see a new moon in our sky because

a new moon is quite near the Sun in the sky

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

Lunar eclipses can occur only during a

full moon

the saros cycle

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

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

stellar parallax

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

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.

All the gas clouds that we see in the Milky Way in our sky lie relatively close to us (at least compared to the size of our entire galaxy).

An angle of 1 arcsecond is

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

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

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

Looking northward, the sky appears to turn _____ over the course of the night.

counterclockwise

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

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

the spring and fall equinoxes

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.

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.

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

new Earth

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

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

A full moon high in the sky

Why is there 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.

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

Earth is stationary at the center of the universe

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.

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

We cannot see a first quarter Jupiter from Earth (or Earth orbit), because Jupiter is so much farther from the Sun than we are.

Which of the following best explains why a solar day is longer than a sidereal day?

Because Earth orbits the Sun at the same time it rotates, Earth must make slightly more than one full rotation between noon one day and noon the next.

transit

when a planet passes in front of the sun

only Mercury and Venus can be seen from Earth

A friend says she saw a planet shining on her meridian at midnight. Which planet can you be sure that she did not see?

Venus or Mercury (bc when the Earth is at midnight it will be facing away from the sun, so it won't see the closer planets)

Suppose you have a time-keeping device that always reads precisely 12:00 when the Sun crosses your meridian. What kind of time is this clock keeping?

apparent solar time

Why does mean solar time differs from apparent solar time?

The length of a solar day is not always exactly 24 hours.

As viewed from any place within the continental United States, noon on apparent solar time is defined as the moment when the Sun is ______.

directly south

why does our calendar have leap years?

A tropical year is slightly more than 365 days.

How do you tell which of these stars lies closest to the north celestial pole on the celestial sphere?

the one with the most positive declination

First Cosmological Model

Developed by Plato, Eudoxus, and Pythagoras

concentric circles

Aristotle

sun is farther than moon

earth is spherical

fundamental theory of natural laws

Sublunar or Earthy Realm

motion is linear

motion requires constant force

cyclic concept of time

earth, water, air, and fire

translunar or celestial realm

natural motion is circular

parallax

As the earth travels around the sun, we will view the nearby stars

from different perspectives (the stars will appear to shift back and

forth every year)

Aristarchus

heliocentric theory

determined moon size and distance

Eratosthenes:

...

Hipparchus

Invented magnitude system

o Apparent brightness depends on the luminosity of the star and its

measured in apparent magnitudes

• fainter objects have large apparent magnitudes

• brighter objects have smaller apparent magnitudes

o round that distance to the moon is 59 times the earths radius,

determined length of year w/in 6 min, couldn't figure out parallax

o devised system using uniform circular motions that could account for

position of sun and moon

Ptolemy

is our main source of info about Greek ASTR

o used parallax to accurately determine distance to the moon

o developed geocentric model of solar system

o system of constellations

retrograde motion

planets appear to move though sky from west to east

o however sometimes it will appear to stop, move backwards, then

forwards again

o retro motion is from east to west