Our Solar System

BIG 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

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 TWO types of planets in our solar system… How were you taught to remember them?

Planet Acronyms My Very Excellent Mother Just Served Us Nachos My Very Excellent Mother Just Served Us Noodles My Very Educated Mother Just Served Us Nachos

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 Heavily cratered Huge temperature range 427ºC in day, -173ºC at night Mariner 10 – visited the planet in 1974 and 1979

B. Venus Earth’s twin (size, mass, density) Rotation direction is opposite that of other planets Pressure is 90x Earth’s Hot surface (464ºC) Dense atmosphere (mostly CO2) Magellan Probe

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 Earth 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 Planets An object that, due to its own gravity, is spherical in shape, orbits the Sun, is not a satellite, and has not cleared the area of its orbit of smaller debris.

1. Pluto (now ‘asteroid #134340’) Late to be discovered (1930) Mostly frozen methane, rock, and ice Demoted from planet status to “dwarf planet” in August 2006 Not always the furthest planet from the sun

Ceres: largest body in the Asteroid Belt Eris: largest known dwarf planet 27% more massive than Pluto

B. Small Solar System Bodies

1. Asteroids thousands orbiting the Sun between Mars and Jupiter rocky bodies vary in diameter pitted, irregular surfaces

Asteroid Belt between Mars and Jupiter remains of unformed planets (planetesimals)

meteoroid: small bits of rocks and metal left by a comet or asteroid collision meteor: bright streak of light produced by meteoroids burning up as they enter our atmosphere meteorite: meteoroid (or part of one) that is left after it hits the Earth

Meteorite: meteoroid that makes it to Earth Meteor Shower Meteorite: meteoroid that makes it to Earth “shooting stars”

When large meteorites strike Earth, they produce impact craters:

2. Comets small, icy bodies of rock, dust, methane and ammonia orbit the Sun in long ellipses

Nucleus: small solid core, which is made up of rocks, metals, and ice Tail: gas and dust

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

The tails always point AWAY from the Sun! Their tails of gas and dust are pushed away by radiation from the Sun.