The Solar System

The solar system is the sun and everything that revolves around the sun.

Models of the Solar System

• Ancient Greeks : the planets, sun and moon were on separate spheres that rotate

• The Greek word “planasthai” means “to wander”.

• This is called the “Earth –Centered” Model of the solar system. ( The Earth is at the center of the universe.)

The Sun –Centered Model of the Solar System

• This is also known as the Heliocentric Model. ( Helios = the sun)

• Polish astronomer, Nicholas Copernicus, gave us the idea that the Earth goes around the sun in 1543. WebSite

Nicholas Copernicus

Nicholas Copernicus

Galileo Galilei: Heliocentric Theory

• Italian astronomer, Galileo Galilei, found evidence that supported a Sun-Centered Model. Rice University’s Galileo Project

Galileo’s Portrait by Tintoretto

The Modern Model of the Solar System:

• Our view of the solar system is constantly changing and improving .

• New moons have been discovered in 2005-2006.• New Kuiper Belt Objects up to 2,100 miles across

have been discovered recently.• Eight planets and many large objects, over 100

moons, asteroids, and comets orbit the sun. • The sun is one of 400 billion stars in the Milky

Way Galaxy. It is typical – 200 extrasolar planets.

A Theory for the Formation of the Solar System

• Scientist have evidence that the solar system was created out of a nebula 5 billion years ago.

• 1) 4.5 billion years ago, Gravity pulled matter inward, and the cloud contracted and began to spin.

• 2) Planets formed as particles collided over years.• The sun formed at the center, and began nuclear

fusion.

Motions of the Planets

• In the 1600s, German mathematician, Johannes Kepler discovered that the planets orbit in an ellipse.

• The orbit of the planets is not a circle, but an oval or ellipse.

• Kepler discovered that the planets move at different speeds.

The Inner Planets

• The Inner Planets are small and rocky, with iron cores.

• Mercury

• Venus

• Earth

• Mars

Mercury

Mercury• The closest planet to the sun.• The Messenger Probe is on its way to study

Mercury. Launched Aug. 3, 2004,arrives March 2011. Web

• Mariner 10 visited in 1975. • There are 3 Km high cliffs that may indicate that

Mercury shrank as its core cooled.• There is a thin atmosphere of hydrogen and

helium., sodium and potassium.• The surface is 450 degrees C to –170 degrees C

Venus

•Its size and mass are similar to Earth. WEB•There is a dense atmosphere, 90 x the pressure of Earth’s. It is mostly carbon dioxide.

Venus

• The gases create a greenhouse effect which keeps the temperature at 470 degrees C.

• The Russians sent many probes to Venus. The U.S.’s Magellan was at Venus from 1990 to 1994, which showed craters, faults, and volcanoes with lava flows.

Earth facts

• Earth is 1 AU ( astronomical unit ) from the sun.

• A key fact is that Earth’s temperatures allow water to exist as a solid, liquid, and gas.

• The Earth’s atmosphere protects life from the sun’s radiation.

MARS Exploration

Odyssey 2001

Viking 1976

Spirit & Opportunity 2004-2006

Mars is red because iron oxide (rust) is on most rocks on the surface of Mars.

Mars Exploration

• U.S. Mars Reconnaissance Orbiter arrived 3/06.

• MRO detected evidence of liquid water 12/06

Evidence of Water --------

MRO 2006

Mars Exploration Present and Future

• NASA Human Mission planned for 2030.

Mars

• Mars has polar ice-caps. The northern cap is thought to be water, while the southern cap is frozen carbon dioxide.

• There are volcanoes, canyons, and deserts on Mars

• U.S. Pathfinder rover visited Mars in 1997.

The Outer Planets

• Most of the outer planets are giant, gas and liquid planets. Most have many moons.

• Jupiter

• Saturn

• Uranus

• Neptune

• Pluto

Jupiter

Many Moons!

The Moon Europa above a ring

Signs of an ocean

Impacts from SL-9

The Great Red Spot

Jupiter

• Jupiter , “The King”, is the largest planet.• Jupiter is made of hydrogen, helium,

ammonia, methane, and water vapor.• There may be a deep ocean of hydrogen and

helium under the thick clouds of gas.• The“Great Red Spot” is a storm which is

bigger than Earth and has lasted at least 400 years.

Moons of Jupiter

• Jupiter has 63 moons (as of 2006). Many have been discovered in the last few years.

• Galileo discovered the four largest in 1610,Io, Europa, Ganymede, and Callisto.Io has volcanoes.Europa has a thick ice crust, a thin oxygen

atmosphere, and oceans, possibly more water than Earth.

Ganymede is the largest moon in the solar system, larger than Mercury.

Volcanoes on Io , the moon of Jupiter

Europa: Moon of Jupiter

NASA’s Planet Web Site

Saturn

Giovanni Domenici Cassini

Italian astronomer who studied Saturn and discovered several of its moons in the 1670s. Web

Saturn

• Saturn has massive rings made of rock and ice.

• There were 33 moons discovered by 2004.• In 2005 , the Cassini probe visited Saturn.• There are 56 moons as of December, 2006.• Titan is the largest moon. It is bigger than

Mercury. Its thick atmosphere appears orange. It has lakes of methane.

Some of Saturn’s Moons

Saturn

• Saturn’s density is so small that it would float on water.

• Saturn is a giant gas and liquid planet of hydrogen, helium, ammonia, methane, and water.

• Under the thick gas atmosphere, there may be a deep ocean. A rocky core may be at the center of Saturn.

WEB NASA Facts

Saturn continued…• The Voyager probes visited Saturn in 1980

& 1981.

• The Cassini probe visited in 2004 - 2006

Cassini Probe 2006

• The ESA probe, Huygens, discovered methane lakes on Saturn’s moon, Titan.

• Titan has a thick , Nitrogen gas atmosphere and appears orange.

• Cassini Probe Web Site

• Saturn’s Moons Web

Uranus

Uranus

• It was not discovered until 1781. Jupiter and Saturn were known in ancient times.

• There are 13 thin rings around Uranus (as of 1/06).

• Uranus’ magnetic

field is tilted 60 degrees

from its rotational poles.

Uranus

• The atmosphere is H, He, and methane. The methane gives it a blue-green color.

• Uranus has 27 moons as of 2005.

• The temperature is – 216 degrees Celsius

Neptune

Neptune

• Neptune is another large gas planet, but it was only discovered in 1846.

• Sometimes Neptune is farther than Pluto.

• The atmosphere is similar to Uranus, and appears blue.

• There are dark blue features like the Great Red spot of Jupiter.

Neptune

• The ‘god of the sea” may have oceans under its thick cloud cover. There probably is a rocky core.

• Voyager discovered six new moons , and the Hubble discovered more. The count for 2005 is 17 moons!

• Neptune has thin rings.• Neptune’s magnetic field is tilted 55 degrees.• One ring appears to be twisted.

Pluto

Pluto: Declassified 9/2006

• Pluto is a dwarf planet in the solar system.

• It is a Trans-Neptunian Object (TNO).

• Pluto has one large moon, Charon, and two other tiny moons, Nix and Hydra

• Pluto was discovered in1930, Charon in 1978. It was demoted Sept., 2006.

• JPL WebSite

Pluto’s New Moons:

• November, 2005: “The candidate moons, Hydra and Nix , approximately 27,000 miles away from Pluto. The objects are roughly two to three times as far from Pluto as Charon.” JPL/NASA web site