Earth, Moon, SunVocabulary

Astronomy

• The study of the moon, stars and other objects in space.

Sphere

• Round 3-dimensional object

• The Earth is shaped like a sphere.

Axis• The imaginary vertical line that goes through

the center of the Earth, the poles are at each end

• The Earth rotates on its axis.

Axis

Rotation• The spinning of earth on its axis, causes day

and night to occur, one rotation takes about 1 day (or 24 hours)

• The Earth makes one rotation every day.

Revolution• Earth’s yearly orbit around the sun, takes

about 365 days

• The Earth’s revolution takes about 1 year to completely go around the Sun.

Orbit

• The path of an object as it revolves around another object in space. Earth follows an elliptical path.

Ellipse• An elongated, closed curve (smashed circle)

• The Sun is at one end of the ellipse, not the center. The Earth travels around the sun in an ellipse.

Solstice• The day when the sun reaches its greatest

distance, North (Summer) or South (Winter) of the equator.

• Summer solstice is on June 21st or 22nd.

• Winter solstice is on Dec 21st or 22nd.

• The summer solstice is about the longest day of the year. The winter solstice is about the shortest day of the year.

Equinox• Occurs when the sun is directly above the equator. • Spring equinox is on Mar 20th or 21st.

• Fall equinox is on Sept 22nd or 23rd.

• During the equinox the number of daylight hours & nighttime hours is nearly equal all over the world.

Seasons on Earth

Moon Phase• Different forms that the moon takes in its

appearance from earth

• The moon phase depends on the relative positions of the moon, earth & sun.

New Moon• The moon is between the Earth & the sun,

lighted ½ faces the sun, dark side faces Earth, see the moon as a dark circle

• The new moon rises and sets with the sun.

Waxing• More of the illuminated (lighted by the sun) ½ of the

moon can be seen each night, it seems to grow bigger

• There are several different phases of waxing moons.

Full Moon• When all of the moon’s surface facing Earth

reflects light from the sun

• The full moon is when you can see the whole moon.

Waning• Less of the illuminated side of the moon can

be seen each night, seems to be shrinking

• Waning occurs after a full moon.

Solar Eclipse• Occurs when the moon moves directly between the

Sun & Earth and casts its shadow over part of Earth. • Umbra is the darkest portion of the moon’s shadow =

total solar eclipse

• Penumbra is the lighter shadow on Earth’s surface = partial solar eclipse

• Never look directly at the sun during a solar eclipse.

Partial Solar Eclipse

Full Solar Eclipse

http://eclipse.gsfc.nasa.gov/SEdecade/SEdecade2011.html

Lunar Eclipse• When Earth’s shadow falls on the moon.

– Lunar eclipses begin when the moon moves into Earth’s penumbra.

– When only a portion of moon moves into Earth’s umbra = partial eclipse

– When the Earth completely blocks the light from the sun = total lunar eclipse

• A total lunar eclipse can be seen by anyone on the nighttime side of Earth, where the moon is not hidden by clouds.

Total Lunar Eclipse

Partial Lunar Eclipse

http://eclipse.gsfc.nasa.gov/LEdecade/LEdecade2011.html

Maria• Dark colored, flat regions of the moon,

formed when ancient lava filled craters on the moon’s surface

• When you look at the moon, the dark spots you see might be maria.

Impact Basin / Crater• The depression left behind by objects striking

the moon

• The Meteor Crater in the state of Arizona was the first crater to be identified as an impact crater.

• The South Pole- Aitken Basin is the largest and deepest impact basin in the solar system.

Moon InfoWhere does the moon’s light come from? • The moon’s light is a reflection of the sun’s light.

Why do the sun & moon appear to be the same size? • Even though the moon is 400 times smaller than the

sun it is 400 times closer to us than the sun.

How does the moon move in the sky? • The moon rises in the East and sets in the West. It

rises & sets about 1 hour later each day.