Astronomy LT2: The Celestial Sphere

Altitude angle

The angle a star makes with the horizon

Zenith

The imaginary point directly above an observer's head (at 90 degree altitude).

Sextant

A device that allows astronomers to measure the altitude of a star in the sky.

The Celestial Sphere

A model that shows what the sky looks like to us as observers on the ground.

Constellations

Groups of stars that appear in different locations throughout the year. 12 of these are the "zodiac" constellations (Cancer, Sagittarius, etc. ) that can tell us what month it is based on what constellation is not visible.

Latitude

How far an observer is from the equator. Measured in degrees , from zero degrees (at the equator) to 90 degrees North/South (at the North or South Pole). On a globe, lines of latitude are horizontal, like a ladder.

Polaris

The "North Star" that is millions of miles above the north pole. To an observer in the Northern hemisphere, how high it appears in the sky (it's altitude) is equal to the latitude on Earth the observer is at.