The Night Sky

Ancient Astronomy Early astronomers paid attention to the sky and were careful to not offend the gods that rule the skies. The time it takes for the Earth to make one revolution around the sun is days. It takes one day for Earth to make one rotation on its axis. The first clocks were pillars and sticks in the ground and people used the shadows they made to tell the time.

Patterns in the Night Sky Many groups of stars seem to form patterns called constellations. They appear to lie very close to each other at exactly the same distance from Earth. They look close together because they lie on the same line of sight. They may actually be many light years apart! One light year is a unit of distance, it is the distance light travels in one year. (9.5 x km)

What constellation is this?

Random stars in space

Apparent Magnitude Star maps show constellations and individual stars. The larger the dot on the map, the larger the star appears to us on Earth. Apparent magnitude is the brightness of a star as seen from Earth

Names of Constellations The International Astronomical Union (IAU) is responsible for naming and classifying celestial objects. There are 88 official constellations. Examples are cancer (crab), Cassiopeia (the queen), Ursa Minor (Little Bear) Smaller groups of stars that form patterns within a constellation are called asterisms. Example is the Big Dipper (a part of the Ursa Major, the Great Bear)

What is this constellation? Ursa Major

Cassiopeia

Polaris and Pointer Stars The Big Dipper’s two end-stars are called the pointer stars because they point toward Polaris (North Star)

Rotation

Revolution

Earth’s Motion The Moon is responsible for the tides (rising and falling of ocean waters) that occur on Earth. Due to the Earth revolving around the Sun, we see different constellations at different times of the year. The path of the Earth’s orbit around the Sun is not a perfect circle, it is an ellipse.

Seasons Earth rotates at a tilt of 23.5 . In the summer months, the northern hemisphere is tilted toward the Sun. Sunlight strikes Earth at different angles

THE MOON the moon orbits Earth every 29.5 days the moon rotates once on its axis as it completes one orbit around Earth as a result, we see only one side of the moon

THE MOON the moon is always half illuminated by the Sun the amount of illumination we see is classified as the phases of the moon

FULL QUARTER CRESCENT GIBBOUS FOUR MAIN SHAPES

Moon Phases Waxing - increasing Waning - decreasing

Name this phase! Full Moon

Name this phase! First Quarter

Name this phase! Waxing Crescent

Name this phase! Waning Gibbous

Name this phase! Third Quarter

Name this phase! Waxing Gibbous

Name this phase! Waning Crescent

Name this phase! New Moon

Name this phase! Waning Crescent

Waxing Crescent

WHAT’S A BLUE MOON? An extra full moon that happens every 2.72 years. A great doo-wop song from the 50s!

LUNAR ECLIPSE Earth’s shadow is divided into 2 parts: the umbra (inner shadow) and the penumbra (outer shadow).

SOLAR ECLIPSE Occurs whenever the shadow of the Moon falls on Earth’s surface, the Moon is between the Sun and the Earth.

SOLAR ECLIPSE