The Celestial Sphere

Question 1

The Celestial Sphere

Answer 1

The sphere of the sky surrounding the earth, representing the stars we see in the sky.

Question 2

Celestial Equator

Answer 2

If the earth’s equator was projected out into space, the line it would make on the celestial sphere is the celestial equator.

Question 3

Celestial Poles

Answer 3

The axis of the earth point at these northernmost and southernmost points on the celestial sphere.

Question 4

Ecliptic

Answer 4

The path the sun takes through the celestial sphere over the course of a whole year; it is tilted with respect to the celestial equator because the earth’s axis is tilted 23.5 degrees.

Question 5

Axis

Answer 5

The line around which the earth rotates.

Question 6

Circumpolar

Answer 6

The stars and constellations that rotate around the north or south celestial pole that are high enough above the horizon they don’t rise or set.

Question 7

The Direction of Spin

Answer 7

Looking down on the north pole, the earth spins counterclockwise. Looking straight at the earth, it spins in an eastward direction. This means the celestial sphere overhead moves in a westward direction from our perspective here on earth. Facing the north celestial pole, it looks like the stars overhead are turning counterclockwise around the pole. Facing the south celestial pole, it looks like the stars are turning clockwise around the pole.

Question 8

Apparent Magnitude

Answer 8

How bright a star appears in our sky

Question 9

Constellation

Answer 9

An official grouping of stars in the sky creating a picture; there are 88 official constellations.

Question 10

Asterism

Answer 10

A group of stars making a recognizable shape in the sky that is not an official constellation.

Question 11

Planet

Answer 11

Originally meant “Wandering star”, meaning it doesn’t move with the fixed stars in the sky; in ancient times this included the sun, moon and 5 classical planets (Mercury, Venus, Mar, Jupiter, and Saturn)

Question 12

Geocentric Model

Answer 12

A model or understanding of the universe where the earth is at the center, and the sun, moon, planets, and stars revolve around the earth.

Question 13

Zenith

Answer 13

From you perspective, the part of the celestial sphere that is right over you head.

Question 14

Meridian

Answer 14

The line on the celestial sphere going from due south, straight over your head through the zenith, to due north; it means “middle of the day”

Question 15

Heliacal Rising

Answer 15

The first sighting of a specific star or constellation right before sunrise.

Question 16

Acronical Rising

Answer 16

When the star rises as the sun is setting, reaching the meridian at high midnight.

Question 17

Axial Precession

Answer 17

The slow wobble of the earth’s tilted axis, taking about 26,000 years.