EXAM 1

Light year:

The distance light can travel in 1 year

Astronomical Unit:

The unit of length defined as the average distance between Earth and the Sun; this distance is about 1.5 × 108 kilometers

Geocentric:

Solar system centered around the Earth

Heliocentric:

Solar system centered around the Sun

EM spectrum:

The whole array or family of electromagnetic waves, from radio to gamma rays

Doppler effect:

The apparent change in wavelength or frequency of the radiation from a source due to its relative motion away from or toward the observer

How do you get the scale size of an object?

Object scale size = object size/scale

How do you get the scale used on a scaled object?

Scale = object size/scale size

Where is your zenith?

The point on the celestial sphere opposite the direction of gravity; point directly above the observer, your 90°

Where is your horizon?

Where the sky meets the ground, in all directions

Which 2 points does the Earth rotate around?

North & South pole

Celestial sphere:

Imaginary dome around the Earth that illustrates the trajectory of objects in our night sky

Celestial poles:

Imaginary lines extending from Earth’s poles, into the celestial sphere

Celestial equator:

Imaginary projection of Earth’s equator onto the celestial sphere, 90° from the celestial poles

What moves the least in the night sky?

Objects closest to the celestial poles, Polaris (north star)

What moves the most in the night sky?

Objects closest to the celestial equator

The apparent motion of the celestial sphere depends on your what?

Latitude

How many degrees does the Sun move each day?

1°

Ecliptic:

The annuel path the Sun appears to take around the celestial sphere

Zodiac Constellations:

The 12 star patterns that follow very close to the ecliptic

Does the ecliptic follow the same path as the celestial equator?

No

How many degrees is the Earth’s tilt?

23.5°

Can you see stars that are under your horizon?

No

Solar day:

Earth’s rotation period as defined by the position of the Sun in the sky; the time between successive passages of the Sun through the meridian

Sidereal day:

Earth’s rotation period as defined by the positions of the stars in the sky; the time between successive passages of the same star through the meridian

How many degrees does the Earth rotate in a solar day?

359°

How many degrees does the Earth rotate in a sidereal day?

360°

How long does it take the Earth to rotate exactly 360°?

23:56, slightly less than 24 hrs

Retrograde:

the apparent westward motion of a planet on the celestial sphere or with respect to the stars

Does the Earth spin in the opposite direction that it orbits?

No, the Earth spins in the same direction that it rotates

Where is the region you could always see a star? (let’s assume the latitude of 30° again)

30° N of your horizon

Solstice:

When the pole is either pointed towards or away from the sun, the shortest or longest day of the year

Which pole faces the Sun during the summer solstice?

North

Which pole faces the Sun during the winter solstice?

South

On the summer solstice, the arctic circle has how many hours of sunlight?

24 hrs

On the summer solstice, the antarctic circle has how many hours of sunlight?

0 hrs

Equinox:

Neither pole is pointed towards or away, day & night are relatively equal in length

What are the 2 reasons why summer is warmer than winter?

In summer, the days are longer and the ground receives more direct sunlight

Does the distance between the Sun and Earth have anything to do with the seasons?

No

What is the brightest thing in the sky?

Sun

What’s the second brightest thing in the sky?

Moon

Name the 8 lunar phases:

New, waxing crescent, 1st quarter, waxing gibbous, full, waning gibbous, 3rd quarter, waning crescent

Is there a part of the moon that never sees the sun?

No

Synchronous rotation:

When a body (for example, the Moon) rotates at the same rate that it revolves around another body

How much of the moon is always in sunlight?

Half