Earth and the solar system

Chapter 9Video

The Earth in Perspective• Diameter = 12 700 km• 1 km = 4 times around a race track • Montreal to Quebec City = 250 km

Moon

• Only natural satellite of the Earth• Diameter = 3 500 km (3.6 times smaller than

Earth)

Distance between the Earth and the Moon

• 384 000 km• It would take 160 days to get to the moon if

you drove at 100 km/h.

3 500 km

12 700 km

384 000 km

Solar System• Composed of a star and the celestial bodies that orbit it (8

planets, 3 dwarf planets, satellites, asteroids, and comets).• The star of the Solar System = the Sun• Sun = source of heat and light. Takes 8 minutes for the light of

the sun to reach Earth.

Measuring large distances in our solar system

• In astronomy, the distances are so huge that larger units of measure are needed.

• Distance between the Earth and the Sun = 1 AU• 1 AU (Astronomical Unit) = 150 000 000 km• Used to measure the distances within the Solar System

1 AU

• Mercury = 0.39 AU• Venus = 0.72 AU• Earth = 1 AU• Mars = 1.52 AU• Jupiter = 5.2 AU• Saturn = 9.54 AU• Uranus = 19.19 AU• Neptune = 30.06 AU

Drawing a model to

scale

Is Pluto a planet?

• Considered a dwarf planet– Not large enough to be considered a planet

• Part of the Kuiper belt

Kuiper Belt• strain of asteroids and comets beyond Neptune

(Pluto is a part of this “belt”)• Discovered in 1992• Distance = 40 AU - 120 AU from the sun• Around 80 AU wide

Oort Cloud• Hypothetical cloud composed of asteroids

and comets• Distance = 40 000 - 150 000 AU from the sun• Limit of our solar system

Measuring distances outside our Solar system- The Light Year

• corresponds to the distance travelled by light in one year. • System of measurement used when dealing outside of the

solar system.

• 1 ly = 9 500 000 000 000 km (63 000 AU)

Galaxy• An enormous collection of stars, gas, dust and matter orbiting around its centre.• Organized by their shape (elliptical, spiral, starburst)• Other stars (like our sun) exist in the galaxy. Some are bigger, smaller, hotter, colder, older,

younger. • Scientists have discovered that there are astral bodies around these stars, which means similar

solar systems to ours may exist.

• We can SEE about 6000 galaxies, but there are probably around 200 000 000 000.

Our galaxy = Milky Way VIDEO

- 100 000 light years in diameter- considered a spiral galaxy

Let’s put it all into perspective!

Where Is Our Solar System Within Our Galaxy?

• 26 000 light years from the middle of the Milky Way

What Would a Galaxy Look Like Within the Universe?

• There are billions of galaxies• Universe is 15 000 000 000 000 light years in distance!