Lesson 2: Celestial Sphere, Constellations, and Sky Coordinates

Flashcards covering the fundamentals of the celestial sphere, Earth's coordinates, apparent motion of the sky, and constellations based on the Lesson 2 transcript.

The __________ is defined as an imaginary sphere of enormous radius surrounding the Earth upon which all celestial objects appear to be projected.

celestial sphere

Astronomers use the celestial sphere as a __________ to describe the positions and motions of celestial objects, even though it is not a real physical object.

useful model

On Earth, __________ is represented by horizontal lines, with the Equator as a key reference point.

Latitude

On Earth, __________ is represented by vertical lines, with the Prime Meridian as a key reference point.

Longitude

Daily motion, or __________, is caused by the Earth's rotation once every $24$ hours.

Diurnal Motion

Diurnal motion leads to the apparent rising and setting of stars in the __________ and west, respectively.

east

__________ occurs as the Earth revolves around the Sun, causing different constellations to become visible during different seasons.

Annual Motion

A(n) __________ is an officially recognized region of the sky containing a recognizable pattern of stars.

constellation

Astronomers currently recognize __________ official constellations established by the IAU.

$$88$$

The acronym IAU stands for the __________, which established the official count of constellations.

International Astronomical Union

Ancient civilizations used constellations for navigation, timekeeping, religious beliefs, storytelling, and __________.

agriculture

In Activity #2, students use an online tool called __________ to find and observe constellations.

Stellarium Web Online

When observing constellations in the "Become a Sky Navigator" activity, students must describe locations using __________.

cardinal directions