The Solar System

The Sun Our sun is considered a star. Right now the sun is considered a “main sequence” star, or one can consider the sun to be an “early adult”. The sun was formed about 4.6 billion years ago and sits at the center of our solar system, around which every planet rotates. As mentioned in the life science unit, the sun is the source of all heat and energy for life on Earth. Note it takes about 8 minutes for light from the sun to reach Earth!

Sunspots

Sunspots refer to dark areas on the surface of the sun. These areas are

“depressed” into the sun’s surface and can be thought of as “storms” on

the surface of the sun.

Solar Flare

Refer to bright eruptions of heat

and light from the sun.

These eruptions eject atoms, ions,

and electrons away from the sun

and even toward us on Earth.

If the solar flare is strong enough, it

can disrupt communication on

Earth by interfering with our

wireless signals!

The Inner Planets

The four planets closest to the sun

comprise the inner planets of the

solar system.

These planets are Mercury, Venus,

Earth, and Mars.

Mercury • A small solid planet without

an atmosphere and dotted

with multiple craters.

• Being the closest planet to

the sun, the surface

temperature can be very hot

(973 degrees Celsius) to

fairly “cold” (373 degrees

Celsius)

• Mercury also has the fastest

orbit around the sun

• No moons orbit this planet

Venus • A hot and rocky planet nearly

the same size as Earth

• Like Mercury, Venus has no

moons

• Venus has an extremely

dense atmosphere of carbon

dioxide

– Because of the atmosphere,

there is a lot of pressure on the

surface of Venus which can

easily crush manmade objects

– “Rain” falls on Venus, but this

rain consists of sulfuric acid

equivalent to our “acid rain”

Venus • A unique fact about Venus is

that the planet spins

“backwards”

• In addition, Venus has the

slowest rotation of any planet.

It takes Venus 243 days to

turn “once”.

– Compare this to Earth, where it

takes 24 hours to turn once.

– A “year” on Venus is longer than

it’s day!

Earth • Our planet, third from the sun

in our solar system

• One moon orbits our planet.

• Atmosphere consists of the

following gases:

– 78% Nitrogen

– 21% Oxygen

– 1% Other Gases

• We’ll talk more about Earth

when we go further into this

unit.

Earth’s Magnetic Field • One of the more important facts about Earth is the

presence of a magnetic field which deflects the wind

from the sun.

• If this field was not there, the sun would strip away our

ozone layer, allowing a lot more UV light to penetrate our

atmosphere.

Mars • Mars is about half the size of

Earth and rotates around the

sun every 687 days.

• A martian “day” however, is

close to ours, ~24 hours

• No liquid water on the surface

but there may be ice in the

polar regions

–It is thought that 3.5-4 billion years

ago Mars did have oceans.

• Two small moons orbit Mars,

Phobos and Deimos

Moons of Mars

The two moons of mars are named Phobos (left) and Deimos (right).

The Asteroid Belt Found between the inner and

outer planets (i.e. between

Mars and Jupiter).

The asteroid belt is a region

in the solar system occupied

by many asteroids, or

irregularly shaped solid

objects (rocks) in space.

Some are very large, some

are very small.

It is thought that the asteroid

belt was a “failed planet”, or

that the material in the belt

failed to form a planet in the

system.

The Outer Planets

Mainly consists of the four gas giants and the dwarf planet Pluto.

Jupiter • The largest planet in the solar

system (11 times the size of

Earth), Jupiter consists of a

metallic hydrogen core

surrounded by a massive

amount of hydrogen and

helium

• Jupiter rotates every 10 hours,

giving the planet the fastest

spin of any planet in the solar

system.

Jupiter Moons

Jupiter has ~67 moons, with four large ones. The names of the large

ones are from left to right: Ganymede, Callisto, Io, and Europa.

The Great Red Spot • Metaphorically equivalent to being a massive “hurricane” or

“storm” on Jupiter.

• The great red spot is three times the size of the Earth!

Saturn • The second largest planet in

the solar system, Saturn is

perhaps best known for its

rings

• Like Jupiter, Saturn is a gas

giant with an atmosphere of

about 75% hydrogen and 25%

helium

• At the center of Saturn is a

rocky core

• Saturn rotates once every 11

hours and completes an orbit

around the sun every 29 years

Saturn’s Rings • The rings on Saturn are

composed of ice.

• As light passes through the ice

orbiting Saturn, it reflects and

produces the colors that we

associate with Saturn’s rings.

Saturn’s Rings • What an artist thinks Saturn’s rings would look like up close.

Moons of Saturn • Officially, Saturn has 53

moons.

• Saturn has one large moon

named Titan.

• Titan’s environment is thought

to resemble that of a primitive

Earth.

• Therefore, it is thought that

given time, life as we know it

may one day appear on Titan.

Uranus • The third largest planet, Uranus

is 4x the size of Earth

• Like Jupiter and Saturn, Uranus

is a gas giant due to its large

cloud layer.

• The natural color of Uranus is

light blue.

• The planet has 27 “moons”, but

none that are really well known

or “famous”

Tilt of Uranus • The most notable feature of

Uranus is how the planet

“spins”.

• Unlike the rotation of other

planets in the solar system,

Uranus has a 90 degree “tilt”.

Neptune • The last gas giant in the solar

system, Neptune takes 165

years to orbit the sun once.

• Neptune has 13 moons, with

one large one named Triton.

• Like Jupiter, Neptune used to

have a large spot called the

great dark spot

• But this spot has been

missing since the voyager 2

probe visited the planet

back in 1989.

Pluto • Demoted a few years ago from a “major planet” to a dwarf

planet

• Pluto takes 248 years to orbit the sun once and has one major

“moon” named Charon

• Light from the sun takes 5.5 hours to reach Pluto

Pluto’s Orbit • Unlike the other planets, Pluto has an elliptical shaped orbit.

• Depending on where Pluto is, sometimes Pluto can be closer

than Neptune is to the sun.