The Structure of Our Solar System Past ideas vs. Current Knowledge Can it change over time?

The solar system consists of the sun, nine planets, their 158 moons and a belt of asteroids and comets. There are over 130 satellites of planets Venus, Earth, Mercury, Mars and the sun are all parts of the inner solar system. Outer solar system consists of Neptune, Saturn, Uranus, Pluto and Neptune. Between the orbits of Mars and Jupiter lies the main asteroid belt. Current Knowledge

Composition Categories Mercury, Venus, Earth, Mars have rocky (terrestrial) terrain. This results in few satellites and rings, high density and slow orbit. Jupiter, Uranus, Saturn and Neptune are gas (Jovian) planets. They are mostly comprised of helium and hydrogen. They are opposite of everything the previous planets. They have many satellites and rings, low density, and quick rotation.

Categories Continued  Giant planets are classified as those with a diameter greater than 48,000 km. These planets are Neptune Uranus, Jupiter and Saturn. Size-  Small planets are those with a diameter than is equal to or less than 13,000 km. These planets are Mercury, Mars, Earth, Venus and Pluto.

When and How the Solar System was Uncovered bodies were revealed more bodies were found major bodies discovered major bodies small moons found

Past Ideas

Heliocentric Theory Proposed by Aristarchus (270 B.C.) He thought that the sun was in the center and all the planets except for the moon orbited around it. He thought that the moon orbited around the Earth. No one believed him at the time because A)They didn’t think the Earth could be moving and people wouldn’t feel it. C) In addition, many believed that Earth had to be the center of the universe because all those people were self- center B) People also believed that if Earth was moving there would have to be a shift in the positioning of the stars

Geocentric Theory Claudius Ptolemy proposed this theory. He then wrote 13 volumes on the motion of planets in 140 A.D. He wrote about Epicycles- circles that the planets orbit on Using epicycles to make backward orbits (retrograde) more visible Ptolemy explained that retrograde was due to western drift. Western drift makes it seem as if its going backwards. Church backed this theory and anyone who went against it was put under house arrest

Copernican Theory Copernicus reinvented the Heliocentric theory and challenged the church’s principles In case you forgot….. This theory stated that the sun was the center Science revolution!! Copernicus still used epicycles to explain motion, but it was more confusing than the Geocentric theory.

Keplerian Theory Used flattened circles or ovals (ellipses) instead of circles for planetary orbits No longer needed the epicycles So far the most accurate system of finding the motion of planets Explained motion by the 1)semi-major axis 2)the peculiarity 3) the inclination 4) the longitude of the ascending bump 5) the argument of the point closest to the approaching planet (perihelion) 6) the time of the perihelion.

Galileo Pioneer of observation Developed laws of motion Found that the Earth is not the center by the fact that 1)spots on the sun 2) mountains on the moon 3) milky way is made up of lots of stars 4) Venus has phases 5) Jupiter has moons

Tycho Brahe and his scientific contributions

Background Information Tycho had the bridge of his nose cut off in a duel, so he was replaced it with a metal plate. Lived on the island of Hven, which is located between Denmark and Sweden, given to him by the Danish King Brahe had a magnificent castle build there, and an underground observatory called Uraniburg. Brahe’s castle was his sanctuary and main center of his astronomy work.

Contributions Tycho invented and calibrated new machines for astronomical observation Brahe and his team observed the bodies and orbits of planets He also corrected his observations according to atmospheric refraction- The change in direction of a ray of light as it passes from space into the atmosphere.

Contributions Cont.  1 st modern database and calculated the distance of planets and starts most accurately for his time  discovered that the sun is farther from the Moon than the Earth  supported geocentric theory  found that planets are on elliptical orbits

Contributions Continued Brahe detected a new star in Cassiopeia Cassiopeia is a constellation He observed a comet and drew the conclusion that the comet is not closer to the Earth than the moon. Aristotle was wrong!

Bibliography “Planets and the Celestial Sphere.” s/lec06.html. 5/10/06 s/lec06.html. 5/10/06 Namowitz, Samuel N. and Nancy E. Spaulding. Earth Science. Canada: D.C Heath and Company, Greogry L. Vogt. Solar System. New York: Scholastic Inc., 2002.

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