Our Solar SystemOur Solar System

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BIGBIG Idea: Idea:

• Using the laws of motion and gravitation, astronomers can understand the orbits and the properties of the planets and other objects in the solar system.

I. Models of the Solar System

A. Geocentric: the Sun, stars, and planets revolved around the

Earth.

– Aristotle promoted

this Earth-centered model

B. Heliocentric – the sun is the center of the universe

- Copernicus proposed this model

Kepler’s Laws• Explained planetary

motion mathematically

1. Law of Ellipses: explains a planet’s path around the Sun

►Ellipse: an oval whose shape is determined by two points (foci)

►The Sun is at one focus of the orbit of a planet

• Because the planets’ orbits are elliptical, they are not always the same distances from the sun…

– Do you remember the word to describe the point in our orbit when we are closest to the Sun?

– Farthest away?

• There are TWOTWO types of planets in our solar system…

• How were you taught to remember them?

Planet AcronymsPlanet Acronyms

• MMy y VVery ery EExcellent xcellent MMother other JJust ust SServed erved UUs s NNachosachos

• MMy y VVery ery EExcellent xcellent MMother other JJust ust SServed erved UUs s NNoodlesoodles

• MMy y VVery ery EEducated ducated MMother other JJust ust SServed erved UUs s NNachosachos

II. The Inner Planets (4 planets closest to the Sun)

• Terrestrial Planets: Earth-like (rocky)

A. Mercury

• Closest to the Sun• Shortest orbit of 88

days

Mariner 10 – visited the planet in 1974 and 1979

•Heavily cratered

•Huge temperature range 427ºC in day, -173ºC at night

B. Venus• Earth’s twin (size,

mass, density)• Rotation direction is

opposite that of other planets

• Pressure is 90x Earth’s

Magellan Probe

Hot surface

(464ºC)

Dense atmosphere (mostly CO2)

C. Earth• Third planet from Sun• Orbital period of 365.24 days• Completes one full rotation in 23 hours 56

minutes• Fifth largest planet• Located between the Sun

and the asteroid belt• One natural satellite, the

moon

Life on EarthEarth is possible because…

• …of the Earth’s distance from the Sun

Temperature is warm enough for water to exist as a liquid

Water occurs on Earth as a solid (ice), a liquid, or a gas (water vapor)

The only known planet with the proper combination of water, temperature, and oxygen to support plant and animal life

Earth’s Atmosphere

What causes the seasons on Earth?

• Earth’s revolution around the Sun, TILTED ON ITS AXIS !

D. Mars• Axis is tilted like Earth’s• Very thin atmosphere (mostly

CO2)

• Olympus Mons – shield volcano Largest known volcano in

our solar system 3X higher than Mt. Everest

Viking 1 – found evidence of water erosion

III. The Outer Planets

• Jovian Planets: Jupiter-like gas giants

A. Jupiter• Largest planet• Fastest rotation - every 10 hours• Orbital period is 12 years• More than 60 moons• Mostly hydrogen and helium• Great Red Spot – giant

rotating storm (over 300 years long)

Galileo

B. Saturn • Average temp: -176ºC• Least dense planet• Orbital period is 29.5 years• Complex system of rings

Cassini Spacecraft

C. Uranus

• Rotates horizontally• The ‘tipped’ planet • Orbital period is 84

years• Greenish color• Methane atmosphere

Voyager 2

D. Neptune

• Orbital period is 164 years• 8 moons and possibly 4 rings• Upper atmosphere composed of white

clouds of frozen methane (appear as bands moving between equator and poles)

• Great Dark Spot – huge storm• Solar system’s strongest winds – exceeding

1,000 km/hr

IV. Other Solar System Objects

A. Dwarf PlanetsA. Dwarf Planets

• An object that, due to its own An object that, due to its own gravitygravity, is , is sphericalspherical in shape, orbits in shape, orbits the Sun, is not a satellite, and has not the Sun, is not a satellite, and has not cleared the area of its orbit of cleared the area of its orbit of smaller debris.smaller debris.

1. PlutoPluto(now ‘asteroid #134340’)

• Late to be discovered (1930)Late to be discovered (1930)• Mostly frozen methane, rock, Mostly frozen methane, rock,

and iceand ice• Demoted from planet Demoted from planet

status to “dwarf planet” in status to “dwarf planet” in August 2006August 2006

Not always the furthest planet from the sun

2.2. CeresCeres: largest body in : largest body in the Asteroid Beltthe Asteroid Belt

3.3. ErisEris: :

• largest known dwarf largest known dwarf planetplanet

• 27% more massive 27% more massive than Plutothan Pluto

B. Small Solar System BodiesB. Small Solar System Bodies

1. Asteroids1. Asteroids

• thousands orbiting the Sun between Mars and Jupiter

• rocky bodies

• vary in diameter

• pitted, irregular surfaces

Asteroid BeltAsteroid Belt

• between Mars and Jupiter

• remains of unformed planets (planetesimals)

meteoroidmeteoroid:: small bits of rocks and metal left by a comet or asteroid collision

meteormeteor:: bright streak of lightlight produced by meteoroids burning up as they enter our atmosphere

meteoritemeteorite:: meteoroid (or part of one) that is left after it hits the Earth

• Meteor Shower Meteor Shower

• Meteorite: meteoroid that makes it to Earth

“shooting stars”

• When large meteorites strike Earth, they produce impact craters:

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2. Comets2. Comets

• small, icy bodies of rock, dust, methane and ammonia

• orbit the Sun in long ellipses

1.1. Nucleus: Nucleus: small solid core, which is made up of rocks, metals, and ice

2.2. Tail:Tail: gas and dust

In relation to the Sun, what do you notice about the tails of the

comets?

• The tails always point AWAYAWAY from the Sun!

• Their tails of gas and dust are pushed away by radiation from the Sun.