The Solar System Chapter 2

Models of the Solar System In the geocentric model, Earth is at the center of the revolving planets. Aristotle stated that the earth was in the center of the solar system. Ptolemy stated that the earth was in the center of the universe. He thought that the planets moved in small circles as they moved around the sun.

Models of the Solar System In the heliocentric model, Earth and the other planets revolve around the sun. This model was developed by Nicolaus Copernicus.

Galileo Used a telescope to view the solar system. Observed the four larger moons that orbited Jupiter. Observed the phases of Venus

Brahe & Kepler Brahe carefully observed the positions of the planets. Kepler had wrote laws that explained the behavior of planets orbiting the sun.

Kepler’s Laws of Motion LAW 1: The orbit of a planet/comet about the Sun is an ellipse with the Sun's center of mass at one focus

Kepler’s Laws of Motion LAW 2: A line joining a planet/comet and the Sun sweeps out equal areas in equal intervals of time

Kepler’s Laws of Motion LAW 3: The farther a planet is from the sun, the longer the orbital period.

Forces that Keeps Planets in Orbit Around the Sun Newton concluded that two factors, inertia & gravity, combine to keep the planets in orbit. Inertia is tendency of an object to resist a change in motion. Gravity is the force that attract all objects toward each other.

The Sun The sun produces its energy from nuclear fusion (core must reach 15 million degree Celsius). Sun’s Atmosphere: The photosphere is the inner layer of the sun that makes light. The chromosphere is the middle layer and produces color. The corona is the outer layer of the sun and produces ultraviolet radiation.

Solar Features Solar winds are a stream of electrically charged particles coming from the corona. Sunspots are areas of gas on the sun that are cooler than the gases around them. Prominences are reddish loops of gas. Solar flares are large explosions of gas on photosphere.

Inner Planets Total of eight planets in our solar system. The inner planets are also called the terrestrial planets. Small in Size. Have rocky surfaces.

Mercury Mercury is 0.4 AU from the sun. Diameter is 4,878 km. Rotates every 59 days. Revolves around the sun every 88 days. Very thin atmosphere. 0 moons. Temperature between -170 o C to 430 o C. Very heavily cratered.

Venus Venus is 0.7 AU from the sun. Diameter is 12,104 km. Rotates every 243 days (retrograde). Revolves around the sun every 225 days. Very thick atmosphere of CO 2. 0 moons. Temperature 460 o C (Greenhouse Effect). Sulfuric acid rain.

Earth Earth is 1.0 AU from the sun. Diameter is 12,756 km. Rotates every 24 hours. Revolves around the sun every days. Atmosphere of 78% nitrogen and 21 % oxygen. 1 moons. Temperature ? o C. 70% of Earth’s surface is covered by water.

Mars Mars is 1.5 AU from the sun. Diameter is 6794 km. Rotates every 24 hours. Revolves around the sun every 687 days. Thin atmosphere of CO 2. 2 moons(Phobos & Deimos). Temperature -153 o C to 20 o C. Polar caps of dry ice. Olympus mons is the largest volcano in the solar system.

Asteriod Belt Asteroids are objects revolving around the sun that are too small and too numerous to be considered planets. The asteroid belt is located between Mars and Jupiter. Asteroids include Ceres, Pallas, Juno and Vesta. Over 300 asteroids have been identified.

Outer Planets (Jovian Planets) Found outside the asteroid belt between the asteroids and the Kuiper Belt. These planets are large and made of gas.

Jupiter Jupiter is 5.2 AU from the sun. Diameter is 142,984 km. Rotates every 9.9 hours. Revolves around the sun every 11.9 years. Thick atmosphere of hydrogen & Helium. 63 moons (Io, Europa, Callisto & Ganymede). Temperature -110 o C. Great Red spot is a large storm. Has a ring system.

Saturn Saturn is 9.6 AU from the sun. Diameter is 120,536 km. Rotates every 10.7 hours. Revolves around the sun every 29.4 years. Thick atmosphere of hydrogen & helium. 60 moons (Titan). Temperature -140 o C. Has an extensive ring system.

Uranus Uranus is 19.1 AU from the sun. Diameter is 51,200 km. Rotates every 17.3 hours. Revolves around the sun every 84 years. Thick atmosphere of hydrogen & helium, with traces of methane. 27 moons. Temperature -195 o C. Has a ring system. Axis is tilted 90 o.

Neptune Neptune is 30 AU from the sun. Diameter is 49,500 km. Rotates every 16.1 hours. Revolves around the sun every 165 years. Thick atmosphere of hydrogen & helium. 13 moons (Triton). Temperature -200 o C. Has an ring system. Had a Great Dark Spot that has since disappeared.

Kuiper Belt The region of the Solar System beyond the planets extending from the orbit of Neptune (at 30 AU) to approximately 55 AU from the Sun.Solar SystemorbitNeptuneAU 55 AUSun

Oort Cloud & Comets The Oort cloud is where the comets are found. Comets are dirty snowballs that orbit the sun. A comet has a head and tail, the head is made of the nucleus and coma. The tail of the comet always points away from the sun because of the solar winds. Halley’s comet appears every 76 years.

Meteoroids, Meteors & Meteorites Meteoroids are pieces of rocks flying through space. Meteors are meteoroids that have entered the earth’s atmosphere, burning up because of friction. Meteorites are meteors that reach the surface of earth.

Life Beyond Earth “Goldilock’s condtions” Liquid water. Suitable temperature. Atmosphere. The Drake Equation: R=The number of suitable stars. F p =The fraction of these stars that have planets. N e =The number of Earth-like planets. F l =The fraction of Earth-like planets where life develops.

Drake Equation(continue) F i =The fraction of life sites where intelligent life develops. F c =The fraction of intelligent life sites where communication develops. L="The "lifetime" (in years) of a communicative civilization. N=The number of communicative civilizations within the Milky Way today.