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Modeling the Solar System Geocentric Model aka Ptolemaic Model Ancient Greeks Earth is at the center of the Universe. The Earth stood still & never moved. Stars are on a separate sphere orbiting the Earth was named after the philosopher Claudius Ptolemy who lived circa 90 to 168 A.D. 7 objects moved differently in the sky known as the “wanderers” or planetai. Sun, Moon, Mercury, Venus, Mars, Jupiter & Saturn Ptolemy Designed an updated model of the geocentric model. The planets orbit in circles around the Earth & also travel in circles on the orbit. Heliocentric Model Nicholas Copernicus Earth revolves around the Sun. Moon revolves around the Earth. Earth rotates on an axis. Planets revolved around the Sun. Planets have circular orbits. Tycho Brahe died of a ruptured bladder because he refused to excuse himself at a banquet as it would have been rude. Tycho had his nose cut off in a duel. He wore a gold and silver prosthetic nose Tycho Brahe & Johannes Kepler Brahe charted the motions of celestial bodies before telescopes. Mathematician Kepler used Brahe’s data to form the Laws of Planetary Motion: 1. The path of a planet around the Sun is an ellipse. 2. A planet will travel faster when it is closer to the Sun & cover a greater distance than when it is farther away. 3. The more distant the planet’s orbit is from the Sun, the longer it takes to make a single revolution. Revolutionary Periods Mercury = 88 Earth days Earth = 365.25 days Jupiter = 11.86 Earth years Pluto = 248 Earth years Nebula Theory: Formation of the Solar System 1. More than 4.6 billion years ago, the solar system was a cloud (nebula) fragment of gas, ice, & dust. 2. Gradually, this cloud fragment contracted into a large, tightly packed, spinning disk. The disk’s center was so hot & dense that nuclear fusion reaction occur forming the Sun. 3. The rest of the material in the disk cools enough to clump into scattered solids. It is estimated that within the entire Universe there are more than a trillion galaxies (the Milky Way itself contains 100 billion stars). This means that there are probably about 100 (to the 22nd power) stars in the entire cosmos. Our sun is a second or possibly 3rd generation star A new star is born in our galaxy every 18 days Scientists believe that we can only see about 5% of the matter in the Universe. The rest is made up of invisible matter (called Dark Matter) and a mysterious form of energy known as Dark Energy. 4. Finally, these clumps collided & combined to become the planets, dwarf planets, comets, asteroids, etc. » The planets all orbit on the same plane called the ecliptic. » The 8 planets occasionally line up in a straight line. Astronomers have discovered more than 150 planets outside our solar system, ranging from 100 to 1,000 times Earth's mass. Gravity and the Solar System Galileo Believed that objects fall to the Earth at the same rate despite the object’s weight. Air resistance slows down falling objects. Sir Isaac Newton Law of Universal Gravitation » Gravity is a force generated between two objects. » Gravity depends on the mass of each object & the distance between them. Gravity Equation F = G m 1 x m2 r2 F is gravitational force r is the distance between the 2 masses m is the mass of an object G is the Gravitational Constant G= 6.673 x 10 -11 m1 r m2 Albert Einstein Theory of General Relativity » Matter tells space how to curve. » Curved space tells matter how to move. » Everything moves in the straightest possible line in curved space-time. The Planets & their Moons Distances in the Solar System Astronomical Units Distances in space are millions of miles/kilometers in the solar system. One astronomical units (AU) is the distance between the Earth & the Sun. 1 AU = 93 million miles = 150 million km Terrestrial Planets Mercury .39 AU from the Sun Named after the Roman messenger god (Hermes) Covered in craters & cliffs, similar to the Moon. No true atmosphere; trace amounts of sodium & potassium. As cold as -170oC in the dark & as hot as 425oC in the light. Mercury is the most iron rich planet in the Solar System with an iron core like Earth. Earth and moon from Messenger (on it’s way to Mercury) The sun's rays are about seven times as strong on Mercury as they are on the Earth. Venus .72 AU from the Sun Its atmosphere is made up mostly of Named after the Roman carbon dioxide. It has clouds made of sulfuric acid! goddess of love & beauty (Aphrodite) Thick atmosphere of CO2 which causes a severe greenhouse effect producing temperatures well over 400oC. (Hottest planet) Air pressure is 90 times greater than the Earth’s. Similar to Earth’s size. Venus is known as Earths' twin sister because of its similar size and proximity to each other. Has retrograde rotation (rotates backwards) Takes longer to rotate than to revolve around the Sun. (Day is longer than its year.) Covered with inactive volcanoes. 3rd brightest object in Earth’s sky. The pressure at the centre of the Earth is 27,000 tons per square inch. The Sun is 330,330 times larger than Earth. Earth 1.0 AU from the Sun Also known as Gaia, Terra, or Home. More than 70% of Earth’s surface is covered in water. Only planet known to have life in existence. Has a natural satellite (Moon/Luna.) Earth spins at ~1100 mph, revolves around the sun a ~67,000 mph, moves (with the solar system) around the Milky Way at ~45,000 mph, the Milky Way hurtles through space at ~500,000 to 660,000 miles per hour. At this moment, the earth is in the middle of the Pliocene-Quaternary glaciation which began ~2.58 mya. We are in an interglacial period which started btw 10k and 15k years ago and my last ~50k years before global glaciations begins again. Mars is red because it is covered in iron oxide (rust). In 1996 NASA, while studying the ALH 84001 meteorite of Martian origin found in Antarctica in 1984, announced that fossilized micro-organisms from Mars might be present in it. Mars 1.5 AU from the Sun Named after the Roman god of war (Ares) Iron oxide (rust) in the soil gives it a reddish color. Polar ice caps made mostly of frozen CO2 (dry ice) & some water. Mars is half the size of the Earth. Global dust storms. Ranges from -125oC at night & 20oC during the day. Phobos Olympus Mons, the largest volcano in the solar system is on Mars. Thin Martian atmosphere of Nitrogen & CO2 Mars has two small moons (Phobos and Deimos) that came from the asteroid belt. Deimos rises and sets twice a day. Deimos Phobos, is moving closer and closer to Mars. Scientists think that one day it will crash into Mars. Jupiter's core is non-metal, but due to the immense pressure inside Jupiter, the core has become a metal. This metal is liquid metallic hydrogen. Jovian Planets Jupiter 5.2 AU from the Sun Named after the Roman king of the gods. (Zeus) Completely made of Hydrogen & Helium gas (gas giant) Largest of the solar planets. Swirling bands of rotating clouds in the upper atmosphere. About 1300 Earths would fit inside Jupiter and the Sun could hold about 1000 Jupiters. Jupiter acts as a huge vacuum cleaner, attracting and absorbing comets and meteors. Some estimates say that without Jupiter’s gravitational influence the number of massive projectiles hitting Earth would be 10,000 times greater. Large rotating hurricane called the Great Red Spot. (2 Earth sizes) 4 faint rings in orbit. 2.5 times greater in mass than all of the other planets combined. Has at least 63 natural satellites, 4 largest are known as the Galilean Moons. The Great Red Spot has been observed for over 300 years! Jupiter is so big that twice the mass of the rest of our Solar System's planets combined would still not be enough to equal its mass. Ganymede » Largest moon in the solar system (bigger than Mercury, but less mass.) » Covered with a crust of rock & ice that is heavily cratered. » Thin atmosphere of Oxygen. Callisto » 3rd largest moon in the solar system » Most heavily cratered object in the system. » Thin atmosphere of CO2. solar Europa » Covered in a shell of ice » A deep ocean beneath the ice shell. » Thin atmosphere of Oxygen. Io » About the size of the Earth’s Moon. » Most volcanically active body in the solar system. Erupts sulfur. » Thin atmosphere of Sulfur dioxide. » No craters. Saturn 9.6 AU from the Sun Named after the Roman god of agriculture. (Cronos) Made of Hydrogen & Helium (gas giant) Flattened poles from spinning very fast. Less dense than water. If you put Saturn in water it would float Most elaborate system of rings (rock & ice debris) 14 or more rings. 56 or more natural satellites. Mimas Titan Dione Titan » 2nd largest moon in the solar system. » Has a thick, dense atmosphere mostly of Nitrogen & some methane. » Surface is “squishy” & has lakes of liquid hydrocarbons. Saturn's moon Titan has hundreds of times more oil and natural gas than all the known reserves on Earth. Even though Neptune is further Uranus from the sun, Uranus is the coldest planet in the solar system. 19.2 AU from the Sun Named after the Greek god of the sky. Gas giant made of Hydrogen, Helium & methane. Rotates on its side. System of rings. 27 or more moons. Uranus was originally named Georgium Sidus or “George’s Star”. On Uranus, each pole gets around 42 years of continuous sunlight, followed by 42 years of darkness. Neptune 30.1 AU from the Sun Named after the Roman god of the sea (Poseidon) Gas giant made of Hydrogen, Helium, & methane. (the methane makes it blue) Near-supersonic & dynamic storms. Faint ring system. 13 known moons Neptune is the stormiest planet. The winds there can blow up to 1,240 miles per hour, that is three times as fast as Earth's Hurricanes. Neptune is so far away that it took the space probe Voyager 2, 12 years to reach it. Triton » Icy, rocky surface. » Coldest body in the solar system (- 37oC) » Icy volcanoes & geysers erupting Nitrogen, dust & methane Dwarf Planets Ceres 2.7 AU from the Sun Largest object in the asteroid belt (950km in diameter.) Classified an asteroid for over 150 years. It is believed to have a rocky core, icy water mantle, & a thin, dusty crust. Technically, Pluto's name is now 134340 Pluto after being declassified as a planet. 39.4 AU from the Sun Named after the Roman god of the underworld (Hades) Second largest dwarf planet in the solar system. Pluto’s companion, Charon , is half the size & doesn’t orbit around Pluto. Pluto & Charon are small enough to fit inside the United States. Pluto is smaller than the Earth's moon. Some astronomers believe that Pluto was once a moon of Neptune but it somehow escaped into its own orbit. Eris 67.7 AU from the Sun Largest known dwarf planet in the solar system with a diameter of 2400km. At least one moon, Dysnomia. Other Possible Dwarf Planets Orcus Sedna Charon Possibly 43 others Other Solar Objects Comets Large chunks of frozen gases, rock & dust orbiting the Sun. (Dirty snowball) 1. Nucleus – main portion of the comet 2. Coma – thawed gases & dust form a bright cloud surrounding the nucleus. 3. Tail – solar winds push away the gases of the coma forming a blue ion tail & a yellowish-white dust tail. If one were to capture and bottle a comet's 10,000 mile vapor trail, the amount of vapor actually present in the bottle would take up less than 1 cubic inch of space. Nucleus Coma Ion Tail Dust Tail Famous Comets Halley’s Comet » Most famous comet » Returns roughly every 76 years. Comet Hale-Bopp » Comet discovered by amateur astronomers. » Last seen Spring of 1997. The comet’s orbit was ~4,200 years but it passed close enough to Jupiter to change it’s orbit. It is now ~2,533 years It will next return to the inner solar system around the year 4385. It was visible to the naked eye for a record 18 months, twice as long as the previous record holder, the Great Comet of 1811. Comet Shoemaker-Levy 9 » Broke into several pieces and collided with Jupiter in 1994. » They created several dark marks in the atmosphere that eventually disappeared. Asteroids Large chunks of rock material left over from the formation of the solar system. Most asteroids are found in the asteroid belt between Mars & Jupiter. If an asteroid hit the Earth, the effect would be similar to gathering ALL the worlds’ nuclear weapons together, and detonating them. Meteoroids, Meteors, & Meteorites Meteoroids are pieces of rock & dust left behind by orbiting comets. Small meteoroids that burn up in the Earth’s atmosphere are called meteors or “shooting stars.” Larger meteoroids that don’t burn up in the atmosphere and hit the Earth are called meteorites.