Our Solar System

I'll tell you one thing about the universe, though. The universe is a pretty big place. It's bigger than anything anyone has ever

dreamed of before. So if it's just us... seems like an awful waste of space.

Right?

Cosmos 2014 Episode 1Start at 4:45 – 15:00

• our solar system is in the Milky Way galaxy• composed of the Sun (yellow dwarf) and

everything that orbits it– sun is 99.8% of the mass

• Planets: 0.135% • Comets: 0.01% ? • Satellites: 0.00005% • Minor Planets: 0.0000002% ? • Meteoroids: 0.0000001% ?

– Sun’s gravity keeps the planets in orbit– around 135 satellites are orbiting the planets

in our solar system• a satellite is an object in orbit around a larger

mass

Characteristics

Formation• about 4.6 billion years old

– probably began as a nebula-- a large cloud of dust in space

– collapsed into a large, rotating, disk-shaped cloud

– continued to collapse and the material in the middle became hot and dense (the Sun)

– planets begin to form by accretion where particles collide and stick together because of gravity

• the planets, moons, and asteroids of our solar system orbit the Sun in about the same angle called the ecliptic plane

Earth’s temperature• tends to be hotter at the

equator because the sun’s energy is perpendicular to the earth and therefore more concentrated

• Earth’s seasons are caused by the tilt (23.5º) of the earth on its axis

• the pole tilted towards the sun is hotter and the days longer – more direct

sunlight and higher temperatures

The Moon

• only natural satellite of Earth• has no atmosphere• gravity is about 1/6 of Earth• light comes from the Sun that is reflected off

the Moon's surface. • moon’s gravity pulls on earth’s water creating

high and low tides.

• phases of the moon– appears to be different shapes depending

on its position relative to earth– waxing is when the moon is “getting”

bigger– waning is when the moon is “getting”

smaller

Eclipses• occurs when one object moves into

the shadow cast by another object– solar eclipse

• moon blocks out the sun from reaching an area on earth

– lunar eclipse• earth blocks the sun from reaching the

moon