Astronomy 1: Introduction to Astronomy

Constellations

designated areas of the night sky

Celestial sphere

imaginary globe around the Earth, organized into 88 constellations or sectors

Circumpolar

Stars and Constellations that circle closely around Polaris, visible all night

Zodiac Constellations

on the same plane as the sun

Rotation

on our axis every 24 hours

Revolution

around the sun, 365 days

Ecliptic

the apparent path of the Sun as it moves the sky during the year

Declination

latitude, North and South of the celestial equator

Right Ascension

longitude, East of the zero line

What in the night sky is “fixed”?

The stars and constellations

What in the night sky is NOT “fixed”?

Planets, the Moon, and the Sun

Celestial Equator

directly above the Earth’s equator

Light Year

unit of measurement for distance, the distance light travels in one year

Zenith

point directly above the viewer’s head

Heliocentric

planets orbit the Sun, Copernicus

Geocentric

Universe orbiting the Earth, Ptolemy

The moon, planets and sun appear to move in the sky because…

…they are so close to us.

Circumpolar constellations examples:

Ursa Major, Ursa Minor, Camelopardalis, Cassiopeia, Draco, and Cepheus

Venus and the Moon are…

…very close and very reflective, making them bright and easily visible to us on Earth

Jupiter and Saturn are…

…very large planets, making them easier to see for us on Earth. Larger and closer than Uranus or Neptune

Polaris

the North Star, directly above the North Pole, found on the tip of Ursa Minor

Eratosthenes

the first person to correctly estimate the circumference of the Earth

Only stars above the horizon are…

…visible to the viewer

The celestial sphere is…

…imaginary. There is no actual globe that contains all the stars in the universe.

Galileo used the…

telescope to view Jupiter, the Moon, and Venus. His findings supported the Heliocentric model

Ptolemy

ancient astronomer who proposed a geocentric model