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Solar system - the sun, all of the planets, & other bodies that travel around it

Planet - a celestial body that orbits the sun, is round because of its own gravity, & has a clear orbital path

The features of a planet depends on its distance from the developing sun.

The four inner planets: Mercury, Venus, Earth, & Mars › Were close to the sun› Heat made them lose lighter elements› Made of large amounts of heavy elements

(iron & nickel) › Are smaller, rockier, & denser

The outer planets are Jupiter, Saturn, Uranus, & Neptune.› formed in the colder

areas far from the sun› B/C of the cold, they

did not lose their lighter elements or their ices

› Called Gas Giants› Composed mostly of

gases, have low density, & are huge

Discovered in 1930

known as the ninth planet

very cold (frozen gases & rocks)

In 2006, astronomers reclassified Pluto as a dwarf planet.

When Earth first formed, it was very hot. In a process called differentiation,

denser materials sank to the center, & less dense materials were forced to the outer layers.

Layers:› Core (iron & nickel)› Mantle (thick layer of iron- and

magnesium-rich rock)› Crust (outermost layer, silica-rich rock)

Outgassing, formed a new atmosphere. › Volcanic eruptions released large amounts

of gases water vapor carbon dioxide Nitrogen Methane sulfur dioxide ammonia

Ozone (03)› formed from

remaining oxygen molecules

› collected in atmospheric layer around Earth

› shielded Earth’s surface from the harmful ultraviolet radiation of the sun

Organisms that could survive in Earth’s early atmosphere developed.› cyanobacteria & early green plants used

carbon dioxide during photosynthesis› produced oxygen as a byproduct› slowly increased the amount of oxygen in

the atmosphere

Over millions of years, rainwater fell to Earth creating freshwater oceans› Rains dissolved some of the rocks on land› carried dissolved solids into the oceans› some of these chemicals combined to form

salts

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1. Geocentric Aristotle suggested an Earth-centered

model of the solar system. Everything revolved around Earth

2. Heliocentric Copernicus proposed a sun-centered

model planets revolved around the sun in the

same direction, but at different speeds & distances from the sun.

Mercury, Venus, Earth, & Mars› Also called terrestrial planets

Terrestrial planets - highly dense planets nearest to the sun› mostly of solid rock and metallic cores› Very few moons

The surfaces of inner planets have bowl-shaped depressions called impact craters› caused by collisions of the planets with other

objects in space

Planet closest to the sun› circles the sun every 88 days› rotates on its axis once every 59 days

Named after messenger of the gods, who moved very quickly.

Heavily cratered & has no atmosphere

Temperatures as high as 427 °C and as low as –173 °C

Second planet from the sun› Goes around the sun every 225 days› rotates very slowly, only once every 243 days› Brightest thing in the night sky

Venus and Earth are of almost the same size, mass, & density . . . But› 92 x hotter (melts lead)› 90 x heavier atmosphere› Clouds of sulfuric acid

Earth is the third planet from the sun.› orbital period = 365 1/4

days› one rotation = 24 hours› one large moon

Geologic records indicate that over the last 250 million years, Earth’s surface has undergone many changes.

Earth’s unique atmosphere & distance from the sun allow water to exist in a liquid state. › Other planets are too close or far away, so that

water boils or freezes

Only known planet that has the proper combination of water, temperature, & oxygen to support life (as we know it).

Fourth planet from the sun› orbital period = 687 days› rotates every 24 hours & 37 minutes

The pressure & temperature are too low for water to exist as a liquid, but . . .

NASA spacecrafts have found evidence that liquid water did exist on Mars’s surface in the past. › features characteristic of erosion by water› ice just below the surface

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Jupiter, Saturn, Uranus, & Neptune› separated from inner planets by a ring of

debris called the asteroid belt

Gas giant - planet that has a deep massive atmosphere

› larger, but much less dense› did not lose their original gases› have ring systems made of dust & icy

debris

Fifth planet from the sun› largest planet› 300 times that of Earth› orbital period =12

years› fastest rotation (10

hours)› has at least 63 moons

(4 are the size of small planets)

› several thin rings

Hydrogen & Helium = 92% of Jupiter

The Great Red Spot is a hurricane-like storm that has been raging for several thousand years.

The Galileo spacecraft measured wind speeds up to 540 km/h. › as high as 30,000 ºC

Sixth planet from the sun› orbital period = 29.5 years› rotates every 10 hours & 30 min› made of hydrogen & helium› has a rocky, iron core› least dense planet in the solar system

Saturn is very cold› average temperature of –176 °C

Saturn has 60 moons› largest moon, Titan, is half the size of

Earth.

Seventh planet from the sun

third-largest planet in the solar system› orbital period = 84 years› at least 27 moons & 12

thin rings› Average temp. = -2140

Uranus’s axis is almost parallel to the plane of its orbit ( turned on it’s side!)› rotates every 17 hours

Eighth planet› solar system’s

strongest winds, which exceed 1,000 km/h

› average temp. = is –225 °C

The Great Dark Spot was a giant storm the size of Earth that appeared & disappeared on Neptune’s surface.

Now a dwarf planet› made of frozen methane, rock, & ice› average temperature of –235 °C› very thin nitrogen atmosphere› three moons