AST101 - Lecture 3

Constellations

Group of stars that looks like a particular shape in the sky and has been given a name

Summer Solstice

• North pole constant sun, constant 

• South pole: Constant night 

• Tropic of Cancer: Sun is directly overhead at summer solstice

• Daylight is longer and darkness is shorter 

• Sun gets higher in the sky, sunlight is more direct 

Fall Equinox

• Sun is exactly above equator 

• Day and night are equal length 

• Rises in the east and sets in the West

Winter Solstice

• North of the arctic circle gets constant nighttime 

• Tropic of Capricorn: Sun is directly overhead on the winter solstice 

• South pole: Gets constant daylight

• Daylight is shorter and darkness is longer 

• Sun does not get as high, so sunlight is at an angle 

• Less sun, so less heat, so it’s colder

Spring Equinox

• Everywhere gets 12-hour days 

• Rises on the easts sets on the west

Why does the Earth has Seasons?

• Earth revolves around the sun 

• Earth’s rotation is tipped 23 degrees away from the ecliptic

• When the earth's axis points towards the sun, it is summer for that hemisphere. When the earth's axis points away, winter can be expected.