Astronomy: Solar System

The Solar System• Consists of the sun, 8 planets, and their moons, and

several kinds of smaller objects that revolve around the sun

Our Solar System’s Only Star:

Only one star

• The Sun is the only star in the solar system

• The sun's light takes about 8 minutes to reach the Earth after it has been emitted from the sun's surface.

• About 109x the size of Earth

The Sun:

• The Sun is a medium sized star

• There are giant stars that are 100x larger than the sun

Our sun in comparison to other stars:

What is a planet? 3 Criteria: 1) An object that orbits a star2) Large enough to become rounded by its own gravity3) Able to clear its own orbit of objects, such as asteroids, meteoroids, other space junk!

The Solar System• The 4 inner planets

(Mercury, Venus, Earth, and Mars) are called terrestrial planets • The outer planets (Jupiter,

Saturn, Uranus, and Neptune) are called gas giants

Relative Sizes of the planets:

Venus MarsMercury

Jupiter Saturn

UranusNeptune

Earth

On your notes, put the planets in order from largest to smallest

Relative Sizes of the planets:

1) Jupiter2)Saturn3)Uranus4)Neptune5)Earth6)Venus7)Mars8)Mercury

Planet Actual Distance from Sun (km)

Mercury 57,900,000

Venus 108,200,000

Earth 149,600,000

Earth’s Moon (Distance from Earth)384,403

Mars 228,000,000

Jupiter 778,400,000

Saturn 1,426,700,000

Uranus 2,866,900,000

Neptune 4,486,100,000

Relative Distances of the planets:

The Earth

• Earth is the third planet from the Sun • Is the largest of

the terrestrial planets

The Moon•Earth’s only natural

satellite •The Moon is in

synchronous rotation with Earth (the same side is always facing the Earth)

The Moon• Size: 3,476 km in diameter

(a little less than the distance across the United States)

•Distance from Earth: 384,403 km (110x the distance across the United States)

The Other planets also have moons:

Planet Number of moons

Jupiter 60+Saturn 31+Uranus 25+Neptune 13+

What’s with Pluto?1. The object must be in orbit around the Sun.

Well, Pluto does that!2. A "planet" has to be big enough that gravity

squeezes it into a round shape. Well, Pluto does that.

3. A planet must be big enough that it's gravity removes other objects that occupy the same orbit.

But Pluto does not meet this criterion.

Poor Pluto…

So, Pluto is considered to be a DWARF PLANET

Plutoids

• A name given for Dwarf planets (like Pluto) beyond Neptune

Asteroids• Rocky objects that are too

small (1-100 km in diameter) and too numerous to be considered planets

• They revolve around the sun in the asteroid belt (between the orbits of Mars and Jupiter)

• Have elliptical orbits

Comets

• Loose collections of ice, dust, and rocky particles

• Revolve around the sun in a very long, narrow elliptical orbit

• Most comets are found in the Kuiper belt (extends beyond Neptune’s orbit) or the Oort cloud

• Main parts: nucleus, coma, and tail

Meteoroid• Chunk of rock

or dust in space

• Come from comets or asteroids

Meteors

• When a meteoroid enters Earth’s atmosphere, friction with the air creates heat and produces a streak of light in the sky called a meteor

Meteorite

• If a meteoroid does not burn up completely, it passes through the atmosphere and hits the Earth’s surface and is called a meteorite

Put the following space objects in order from LARGEST to SMALLEST:

PlanetAsteroidStar Moon