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
Viking 1976
Spirit & Opportunity
2004-2006
Mars is red because iron oxide (rust)
is on most rocks on the surface of
Mars.
Odyssey 2001
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
Signs of an ocean
Many Moons!
The Great Red
Spot
The Moon Europa
above a ring
Impacts from SL-9
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
WEB NASA Facts
• 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.
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