Astronomy Chapter 2

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

If you are located in the Northern Hemisphere, which of the following correctly describes a relationship between the sky and your location?

What kind of path could not be a real orbit for a planet around the sun?

Kepler's first law tells us that the orbit of a planet must be an ellipse with the Sun at one focus. Therefore, the path that shows the Sun in the center of the ellipse, rather than at a focus, cannot be the real orbital path of a planet. (Note that the circular path is allowed because a circle is an ellipse in which both foci are at the center.)

Define Meridian

Line passing through zenith and connecting N and S points on the horizon

Why do we see phases of the Moon?

Lunar phases are a consequence of the Moon's 27.3-day orbit around Earth.

A solar eclipse is when

The Moon's shadow is projected on Earth

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

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

Define Zenith

The point directly overhead

When do eclipses occur?

Two conditions must be met to have an eclipse 1. It must be a full moon (for a lunar eclipse) or a new moon (for a solar eclipse). AND 2. The Moon must be at or near one of the two points in its orbit where it crosses the ecliptic plane (its nodes).

The North Star (Polaris) is 50° above your horizon, due north. Where are you?

You are at latitude 50°N.

Why do the constellations we see depend on latitude and time of year?

- They depend on latitude because your position on Earth determines which constellations remain below the horizon. - They depend on time of year because Earth's orbit changes the apparent location of the Sun among the stars.

How do you calculate angular size

angular size = physical size x (360 degrees/(2pi x distance)

A solar eclipse that occurs when the new moon is too far from Earth to completely cover the Sun can be either a partial solar eclipse or a(n)

annular eclipse

Anyone looking from the night side of Earth can, in principle, see a(n)

total lunar eclipse

A(n) ___ can occur only when the Moon is new and has an angular size larger than the Sun in the sky.

total solar eclipse

A partial lunar eclipse begins when the Moon first touches Earth's

umbra

Define waxing

• Moon visible in afternoon/evening • Gets "fuller" and rises later each day

Define waning

• Moon visible in late night/morning • Gets "less" and sets later each day

The angular size of your finger at arm's length is about 1°. How many arcseconds is this?

60 arcminutes x 60arcseconds = 3600 arcseconds

What do astronomers mean by a constellation?

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

Which of the following celestial objects do NOT rise in the east and set in the west, as viewed from Earth? (Assume that all of these objects are visible from your location on Earth, and that none of them are circumpolar.) A. galaxies B. the Sun C. stars D. the Moon E. All of these objects rise in the east and set in the west.

All of these objects rise in the east and set in the west.

Define Horizon

All points 90° away from zenith

a Lunar eclipse is when

Earth's shadow is projected on the Moon

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

circumpolar

Suppose you live at a mid-latitude in the Southern Hemisphere (such as in Australia, New Zealand, Chile, or South Africa). When will you have 12 hours of daylight and 12 hours of darkness?

on both the March and September equinoxes

Define Equinox

equinox means "equal night," so the two equinoxes are the dates on which all locations (except the poles) have equal amounts of daylight and darkness

A point at which the Moon crosses Earth's orbital plane is called a(n)

node

Solar eclipses can be ____ , _____ or _____

partial, total, or annular.

During some lunar eclipses, the Moon's appearance changes only slightly, because it passes only through the part of Earth's shadow called the

penumbra

Lunar eclipses can be ____ , _____ or _____

penumbral, partial, or total.

Longitude

position east or west of prime meridian (runs through Greenwich, England)

Latitude

position north or south of equator

Define umbra

the fully shaded inner region of a shadow cast by an opaque object, especially the area on the earth or moon experiencing the total phase of an eclipse.

What is the ecliptic?

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