Transcript Introducing the Sun-Earth

Warm-up: How far is an Astronomical
Unit?
• Go over 10 questions
• Sun – Earth - Moon System Notes
• Sun – Earth – Moon System
• Homework: Finish the lab.
Introducing the Sun-Earth-Moon
System Notes
Lesson 2
Background Info
• The Sun is the only star in our solar system.
• The other stars we see at night are part of a
larger galaxy
• A galaxy is a collection of dust, gas, and stars.
Ours is called the “Milky Way.”
• Our Solar system is just a small part of the “Milky
Way” galaxy.
• Our sun is just an “average star” and one of 100
billion or so stars in our galaxy. Joined by billions
of other galaxies in the universe.
• The term “average star” is how astronomers
classify stars by temperature, luminosity, and
mass. The sun is not unusually hot or cold, old or
young, or large or small.
Distances in Space
• Though the Sun seems close to the Earth, it is about
150 million km (93 million miles ) away or about
12,000 Earths away.
• The Sun’s diameter is 1,392,000 km (864,327 miles).
The Earth’s diameter is 12,756 km (7,926 miles).
One million Earths could fit inside of the Sun.
• The Moon’s diameter is 3,500 km (2,159 miles).
• The Moon and the Sun look to be similar sizes
because the moon is about 400 times smaller
than the Sun but also about 400 times closer than
the Sun.
• The Earth’s distance from the Sun (150 million
km) is used as a standard unit for measuring
distances in space. This unit is known as an
Astronomical Unit or AU.
• Jupiter is 778,400,000 km from the Sun or 5.2 AU.
• About 12,000 Earths could fit between the
Earth and the Sun.
• About 30 Earths could fit between the Earth
and the Moon.
• About 109 Earths would equal the diameter of
the Sun.
Movement of the Earth
• Rotation – Indicates the spinning of an object on
a central axis. Earth makes 1 rotation about every
24 hours.
• Revolution – Means the orbiting of on object
around another. Earth makes 1 revolution about
every 365 days.
• We will commonly use the word “Orbit” to
describe a “Revolution.”
• The orbit of the Earth around the Sun is an
elliptical orbit. The orbit of the Moon around
the Earth is nearly a circular orbit.
• The Moon rotates on its axis in about 27.32
days.
• The Moon makes one orbit of the Earth in
about 27.32 days.