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Slide 2 Geocentric vs Heliocentric Geo means Earth Geo means Earth Helio means sun Helio means sun Slide 3 Ancient Observations The ancient Greeks observed the sky and noticed that the moon, sun, and stars seemed to move in a circle around the Earth. The ancient Greeks observed the sky and noticed that the moon, sun, and stars seemed to move in a circle around the Earth. It seemed that the Earth was not moving and everything in the heavens revolved around the Earth. It seemed that the Earth was not moving and everything in the heavens revolved around the Earth. As it turned out, it was very difficult to prove that the planets did not revolve around the Earth without leaving the planet. As it turned out, it was very difficult to prove that the planets did not revolve around the Earth without leaving the planet. Slide 4 Wandering Stars The Greeks also noticed that while the stars move across the sky, their patterns do not change. The Greeks also noticed that while the stars move across the sky, their patterns do not change. But five points of light did move among the stars. But five points of light did move among the stars. The Greeks called these objects planets, which means wandering star. The Greeks called these objects planets, which means wandering star. They made careful observations of these planets, which we call Mercury, Venus, Mars, Jupiter, and Saturn. They made careful observations of these planets, which we call Mercury, Venus, Mars, Jupiter, and Saturn. Slide 5 Geocentric Theory Ancient Greeks such as Aristotle believed that the universe was perfect and finite, with the Earth at the exact center. Ancient Greeks such as Aristotle believed that the universe was perfect and finite, with the Earth at the exact center. This is the geocentric theory, which stated, the planets, moon, sun, and stars revolve around the Earth. This is the geocentric theory, which stated, the planets, moon, sun, and stars revolve around the Earth. Slide 6 Ptolemy (85-165 AD) In AD 140 the Greek astronomer Ptolemy revised the geocentric model to explain all the planetary motions. In AD 140 the Greek astronomer Ptolemy revised the geocentric model to explain all the planetary motions. His model had the planets move in little circles that also moved in bigger circles. His model had the planets move in little circles that also moved in bigger circles. This belief persisted for about 1500 years. This belief persisted for about 1500 years. Slide 7 Copernicus (1473-1543) In the early 1500s the polish astronomer Copernicus suggested that the Sun, not Earth, was the center of the solar system and the planets revolved around it. In the early 1500s the polish astronomer Copernicus suggested that the Sun, not Earth, was the center of the solar system and the planets revolved around it. This is the Heliocentric Theory. This is the Heliocentric Theory. Helios means sun Helios means sun in Greek. in Greek. Slide 8 Problems with Geocentric Theory? Galileo first saw evidence that objects revolved around something besides the Earth when he found Jupiter's Moons Galileo first saw evidence that objects revolved around something besides the Earth when he found Jupiter's Moons Galileo also saw that Mercury and Venus went through phases, just like our moon. The outer planets Mars, Jupiter and Saturn did not. Galileo also saw that Mercury and Venus went through phases, just like our moon. The outer planets Mars, Jupiter and Saturn did not. Slide 9 Heliocentric Theory Prevails Galileo supported Copernicus theory which clashed with the religious views of the time, he underwent many trials and tribulations, and was even sentenced to house arrest for his remaining years. Galileo supported Copernicus theory which clashed with the religious views of the time, he underwent many trials and tribulations, and was even sentenced to house arrest for his remaining years. His view has withstood the test of time. His view has withstood the test of time. Today we talk about our Solar System, not our Earth system Today we talk about our Solar System, not our Earth system Slide 10 Whats Gravity? Gravity is the force of attraction between any two objects with mass. Gravity is the force of attraction between any two objects with mass. The more mass, the more gravity. The more mass, the more gravity. The further apart the two objects are, the less gravity. The further apart the two objects are, the less gravity. Slide 11 What force keeps the planets in their orbits? Gravity acts on all objects on Earth, and the universe, even YOU! Gravity acts on all objects on Earth, and the universe, even YOU! This gravitational attraction pulls the planets toward the Sun as they move through space. Instead of flying off into space, the planets move in orbits around the Sun. This gravitational attraction pulls the planets toward the Sun as they move through space. Instead of flying off into space, the planets move in orbits around the Sun. There is gravitational attraction between the sun and each planet. There is gravitational attraction between the sun and each planet. Slide 12 Our Solar System Slide 13 Our solar system is made up of: Sun Sun Eight planets Eight planets Their moons Their moons Dwarf Planets Dwarf Planets Asteroids Asteroids Comets Comets Meteors Meteors Slide 14 Getting to know our Sun! The sun is just a medium sized star or yellow dwarf. It is about 1.4 million kilometers in diameter The sun is just a medium sized star or yellow dwarf. It is about 1.4 million kilometers in diameter It would take 10 Jupiters or 109 Earths to fit across the Sun! It would take 10 Jupiters or 109 Earths to fit across the Sun! Makes life on our planet possible by giving us great amounts of light and heat. Makes life on our planet possible by giving us great amounts of light and heat. Slide 15 Composition of the Sun The sun is mainly composed of hydrogen and helium. The sun is mainly composed of hydrogen and helium. 90 % hydrogen 90 % hydrogen 9 % helium 9 % helium Small amounts of other elements including oxygen, neon, and carbon are also found in the sun. Small amounts of other elements including oxygen, neon, and carbon are also found in the sun. Slide 16 Distances in space are huge so they have a special measurement system. Slide 17 Astronomical Units We use AU to measure distances in the solar system. We use AU to measure distances in the solar system. The Earth is about 150,000,000-km (93,000,000 miles) on average from the sun. The Earth is about 150,000,000-km (93,000,000 miles) on average from the sun. So we will call this distance 1 AU. So we will call this distance 1 AU. Slide 18 How can I remember the planets? Slide 19 Planets Mnemonic My Very Energetic Mother Just Served Us Nachos! Slide 20 The 8 Planets Mercury Mars Uranus Venus Jupiter Neptune Earth Saturn Slide 21 Planetary Zones First Zone: Contains the rocky terrestrial planets Mercury to Mars. First Zone: Contains the rocky terrestrial planets Mercury to Mars. Asteroid belt divides the first and second zones. Asteroid belt divides the first and second zones. Second Zone: Contains the gas giants Jupiter through Neptune. Second Zone: Contains the gas giants Jupiter through Neptune. Third Zone: Goes from the orbit of Neptune out to 50 AU. Includes Pluto and the ice dwarfs in the Kuiper Belt. Third Zone: Goes from the orbit of Neptune out to 50 AU. Includes Pluto and the ice dwarfs in the Kuiper Belt. Slide 22 The Inner Planets Planets are rocky. Planets are rocky. Called terrestrial from the Latin word terra, which means Earth. Called terrestrial from the Latin word terra, which means Earth. Slide 23 The Outer Planets Jupiter Saturn Uranus Neptune Pluto Called the Gas Giants Made of the lightweight elements Hydrogen, Helium, Carbon, Oxygen, and Nitrogen. The Dwarf Planet--Pluto, not a gas giant, but made of rock and extremely cold. Slide 24 Mercury Mercury has been known since ancient times. Mercury has been known since ancient times. Johann Schroeter (1745 to 1816) was the first to observe the planet Mercury. Johann Schroeter (1745 to 1816) was the first to observe the planet Mercury and record detailed drawings of Mercury's surface features. Mercury is the planet to our Sun and the planet in our Solar System Mercury is the closest planet to our Sun and the fastest moving planet in our Solar System Mercury has a very elliptical orbit and a huge range in temperature. During the long daytime the temperature is hotter than an oven; during the long night the temperature is colder than a freezer. Mercury has a very elliptical orbit and a huge range in temperature. During the long daytime the temperature is hotter than an oven; during the long night the temperature is colder than a freezer. Slide 25 Distance from the sun: 0.39 AU Distance from the sun: 0.39 AU Rotation Time: 58.7 Earth days Rotation Time: 58.7 Earth days Revolution Time: 87.96 Earth days Revolution Time: 87.96 Earth days Diameter: 4,878 km (3,031 miles), about 1/3 the size of Earth! Diameter: 4,878 km (3,031 miles), about 1/3 the size of Earth! Virtually no atmosphere, trace amounts Hydrogen & Helium Virtually no atmosphere, trace amounts Hydrogen & Helium Surface Conditions: Craters with smooth plains, much like the Earths moon, and most extreme temperature range. Surface Conditions: Craters with smooth plains, much like the Earths moon, and most extreme temperature range. Temperature range 800 to -300F No life because practically no atmosphere No life because practically no atmosphere No moons or rings No moons or rings Slide 26 Venus is a planet on which a person would asphyxiate in the poisonous atmosphere, be cooked in the extremely high heat, and be crushed by the enormous atmospheric pressure. Venus was discovered by Ancient Greeks Venus is a planet on which a person would asphyxiate in the poisonous atmosphere, be cooked in the extremely high heat, and be crushed by the enormous atmospheric pressure. Venus was discovered by Ancient Greeks Venus is the second planet from the sun and the hottest planet in our solar system. Venus is the second planet from the sun and the hottest planet in our solar system. Venus Slide 27 This planet is covered with fast-moving sulphuric acid clouds which trap heat from the Sun. This planet is covered with fast-moving sulphuric acid clouds which trap heat from the Sun. Since Venus takes 7.5 Earth months to revolve around the sun and 8 months to rotate once on its axis, Since Venus takes 7.5 Earth months to revolve around the sun and 8 months to rotate once on its axis, a day on Venus is longer than its year. Venus also rotates east to west, the only planet to do so. This (backward) was probably caused by Venus being struck by a large object early in its history. Venus also rotates east to west, the only planet to do so. This retrograde rotation (backward) was probably caused by Venus being struck by a large object early in its history. of any of the other planets. Venus is the closest to Earth in size and mass of any of the other planets. Slide 28 Distance from the Sun: 0.723 AU Distance from the Sun: 0.723 AU Rotation Time: 243 Earth days Rotation Time: 243 Earth days Revolution Time: 224.68 Earth days Revolution Time: 224.68 Earth days Diameter: 12,104 km (7,521 miles) Almost same size as the Earth. Diameter: 12,104 km (7,521 miles) Almost same size as the Earth. Atmosphere: Very Thick Atmosphere, about 96% CO 2, and 4 % N 2. The clouds are mainly sulfuric acid. Atmosphere: Very Thick Atmosphere, about 96% CO 2, and 4 % N 2. The clouds are mainly sulfuric acid. Surface Conditions: Venus has rocks, mountains, craters, and strange dome shape landforms not found on other planets. Surface Conditions: Venus has rocks, mountains, craters, and strange dome shape landforms not found on other planets. Temperature: Average Daily 464F (Earth 59C Temperature: Average Daily 464F (Earth 59C) Life - Very doubtful, the pressure and temperatures are too high. Life - Very doubtful, the pressure and temperatures are too high. No moons or rings No moons or rings Slide 29 VENUS-EARTH COMPARISONS Slide 30 Earth At the equator, the Earth's surface moves 40,000 kilometers in 24 hours. That is a rotational speed of about 1040 miles/hr (1670 km/hr). At the equator, the Earth's surface moves 40,000 kilometers in 24 hours. That is a rotational speed of about 1040 miles/hr (1670 km/hr). The Earth revolves around the Sun at a speed of about 30 km/sec. The Earth revolves around the Sun at a speed of about 30 km/sec. This compares with the Earth's rotational speed of approximately 0.5 km/sec (at middle latitudes - near the equator). This compares with the Earth's rotational speed of approximately 0.5 km/sec (at middle latitudes - near the equator). Slide 31 Distance from the Sun: 1 AU Distance from the Sun: 1 AU Rotation: 24 hours (1 day) Rotation: 24 hours (1 day) Revolution: 365.25 Days Revolution: 365.25 Days Diameter: 12,756 km (7,926 miles) 1 earth Diameter: 12,756 km (7,926 miles) 1 earth Atmosphere: 78% Nitrogen, 21% Oxygen Atmosphere: 78% Nitrogen, 21% Oxygen Surface Conditions: water world, moderate temperature and pressures Surface Conditions: water world, moderate temperature and pressures Temperature: -127F to 136F The coldest recorded temperature was on the continent of Antarctica (Vostok in July, 1983). The hottest recorded temperature was on the continent of Africa (Libya in September, 1922). Temperature: -127F to 136F The coldest recorded temperature was on the continent of Antarctica (Vostok in July, 1983). The hottest recorded temperature was on the continent of Africa (Libya in September, 1922). Life: teeming with life. Planet is for life as we know it. Life: teeming with life. Planet is just right for life as we know it. No Rings No Rings Satellites: 1 Name: Moon Satellites: 1 Name: Moon Slide 32 Mars Mars has been known since ancient times. Mars has been known since ancient times. Mars, the red planet, is the fourth planet from the sun and the most Earth-like planet in our solar system. Mars, the red planet, is the fourth planet from the sun and the most Earth-like planet in our solar system. Mars seems to have dried river and lake beds, deltas, and other features that make scientists think Mars had abundant water early in its history. Mars seems to have dried river and lake beds, deltas, and other features that make scientists think Mars had abundant water early in its history. If there was water it is possible that life could have existed on Mars, and still might. If there was water it is possible that life could have existed on Mars, and still might. Slide 33 Distance from the Sun: 1.5 AU Distance from the Sun: 1.5 AU Rotation: 1.026 Earth Days Rotation: 1.026 Earth Days Revolution Time: 686.98 Earth Days Revolution Time: 686.98 Earth Days Diameter: 6,787 km (4,222 miles) Diameter: 6,787 km (4,222 miles) the size of Earth Atmosphere: 95% carbon dioxide (CO2), 3% nitrogen, and 1.6% argon (there is ). Atmosphere: 95% carbon dioxide (CO2), 3% nitrogen, and 1.6% argon (there is no oxygen). Surface Conditions: large canyons, volcanoes, ancient dried up lakes, streams, rivers, and seas. Surface Conditions: large canyons, volcanoes, ancient dried up lakes, streams, rivers, and seas. Temperature: Ranges from a high of 68 F(20 C) to a low of -220 F(-140 C). Mars is much colder than the Earth. Temperature: Ranges from a high of 68 F(20 C) to a low of -220 F(-140 C). Mars is much colder than the Earth. Life: Possibly ancient life when there was liquid water on the planet. Could still exist under the sand. Life: Possibly ancient life when there was liquid water on the planet. Could still exist under the sand. No Rings No Rings Satellites: 2 very small moonsName: Phobos & Diemos. Satellites: 2 very small moonsName: Phobos & Diemos. Slide 34 Jupiter Jupiter has been well-known since ancient times. Jupiter has been well-known since ancient times. Jupiter is the fifth and. Jupiter is the fifth and largest planet in our solar system. Has a great red spot (which is a storm). Has a great red spot (which is a storm). Jupiter is made up of gases and liquids, so as it rotates,. Jupiter is made up of gases and liquids, so as it rotates, its parts do not rotate at exactly the same rate. Slide 35 Distance from the Sun: 5.203 AU Distance from the Sun: 5.203 AU Rotation: 9.84 Earth Hours Rotation: 9.84 Earth Hours Revolution: 11.862 Earth Years Revolution: 11.862 Earth Years Diameter: 142,796 km (88,729 miles).. Jupiter is so big that all the other planets in our Solar System could fit inside Jupiter (if it were hollow). Diameter: 142,796 km (88,729 miles). 11 times the diameter of the Earth. Jupiter is so big that all the other planets in our Solar System could fit inside Jupiter (if it were hollow). Atmosphere: 90% Hydrogen, 10% Helium Atmosphere: 90% Hydrogen, 10% Helium Surface Conditions: made of gases and liquids Surface Conditions: made of gases and liquids Temperature: Cloud-tops average -153C = -244F. Temperature: Cloud-tops average -153C = -244F. Life: No Life: No Ring 1Composed of: Dust Ring 1Composed of: Dust Satellites: 39 Names: Callisto, Europa, Ganymede, Io Satellites: 39 Names: Callisto, Europa, Ganymede, Io Slide 36 Slide 37 Saturn Saturn has been known since ancient times. Saturn has been known since ancient times. Saturn is the sixth planet from the sun in our solar system. It is the second-largest planet in our solar system. Saturn is the sixth planet from the sun in our solar system. It is the second-largest planet in our solar system. Slide 38 Distance from the Sun: 9.539 AU Distance from the Sun: 9.539 AU Rotation: 10.2 Earth Hours Rotation: 10.2 Earth Hours Revolution: 29.456 Earth Years Revolution: 29.456 Earth Years Diameter: 120,660 km (74,600 miles). Diameter: 120,660 km (74,600 miles) 764 Earths could fit inside a hollowed-out Saturn. Atmosphere: 97% Hydrogen gas, 3% helium 0.05% methane & ammonia Atmosphere: 97% Hydrogen gas, 3% helium 0.05% methane & ammonia Surface Conditions: a gaseous planet with a rocky core, a liquid metallic hydrogen layer above the core Surface Conditions: a gaseous planet with a rocky core, a liquid metallic hydrogen layer above the core Temperature: avg. (cloud tops) is -185 C; -290 F Temperature: avg. (cloud tops) is -185 C; -290 F Life: No Life: No Rings: 7 divisionsComposed of: Ice chunks and rock Rings: 7 divisionsComposed of: Ice chunks and rock Satellites: 33Name: Titan (the largest), Rhea, Iapetus, Dione, Tethys, Enceladus, Mimas, Hyperion, Phoebe, Janus, Epimetheus, Pandora, Prometheus, Helene, Telesto, Atlas, Calypso, Pan Satellites: 33Name: Titan (the largest), Rhea, Iapetus, Dione, Tethys, Enceladus, Mimas, Hyperion, Phoebe, Janus, Epimetheus, Pandora, Prometheus, Helene, Telesto, Atlas, Calypso, Pan Slide 39 SATURN- COMPARISON SATURN-EARTH COMPARISON Slide 40 Uranus Uranus was discovered by the British astronomer William Herschel on March 13, 1781. Uranus was discovered by the British astronomer William Herschel on March 13, 1781. Uranus' rotational axis is strongly tilted on its side (97.9). Instead of rotating like all the other planets in our Solar System, Uranus rotates on its side. This tipped rotational axis causes extreme seasons on Uranus. Uranus' rotational axis is strongly tilted on its side (97.9). Instead of rotating like all the other planets in our Solar System, Uranus rotates on its side. This tipped rotational axis causes extreme seasons on Uranus. This gas giant is the third- largest planet in our Solar System This gas giant is the third- largest planet in our Solar System Slide 41 Distance from the Sun: 19.18 AU Distance from the Sun: 19.18 AU Rotation: 17.9 Earth Hours Rotation: 17.9 Earth Hours Revolution: 84.07 Earth Years Revolution: 84.07 Earth Years Diameter: 51,118 km (32,600mi.) Diameter: 51,118 km (32,600mi.) 4 times the diameter of Earth Atmosphere: 83% hydrogen, 15% helium & 2% methane. Uranus' blue color is caused by methane (CH4) in its atmosphere Atmosphere: 83% hydrogen, 15% helium & 2% methane. Uranus' blue color is caused by methane (CH4) in its atmosphere Surface Conditions: Uranus is a frozen, gaseous planet with a molten core. Surface Conditions: Uranus is a frozen, gaseous planet with a molten core. Temperature: Cloud layer -350F (59 K) Temperature: Cloud layer -350F (59 K) Life: No Life: No Rings: 11Composed of: Rocks and Dust Rings: 11Composed of: Rocks and Dust Satellites: 22 Names: Oberon, Titania, Umbriel, Ariel Satellites: 22 Names: Oberon, Titania, Umbriel, Ariel Slide 42 Slide 43 Neptune Neptune was the first planet whose existence was predicted mathematically. Neptune was the first planet whose existence was predicted mathematically. The calculations were done independently by both J.C. Adams and Le Verrier. Neptune was then observed by J.G. Galle and d'Arrest on September 23, 1846. The calculations were done independently by both J.C. Adams and Le Verrier. Neptune was then observed by J.G. Galle and d'Arrest on September 23, 1846. Neptune is the eighth planet from the sun in our solar system. This giant, frigid planet has a hazy atmosphere and strong winds. Neptune is the eighth planet from the sun in our solar system. This giant, frigid planet has a hazy atmosphere and strong winds. Slide 44 Distance from the Sun: 30.06 AU Distance from the Sun: 30.06 AU Rotation: 19.1 Earth Hours Rotation: 19.1 Earth Hours Revolution: 164.81 Earth Years Revolution: 164.81 Earth Years Diameter: 48,600 km (30,200 mi) Diameter: 48,600 km (30,200 mi) Atmosphere: 74% Hydrogen, 25% Helium and 1% Methane Atmosphere: 74% Hydrogen, 25% Helium and 1% Methane Surface Conditions: Composed mostly of ice, hydrogen and helium. It may have a small, rocky core, and an icy mantle that blends into the atmosphere. Surface Conditions: Composed mostly of ice, hydrogen and helium. It may have a small, rocky core, and an icy mantle that blends into the atmosphere. Temperature: avg. temp. -200C (-328F). Temperature: avg. temp. -200C (-328F). Life: No Life: No Rings: 3 Composed of: small rocks and dust Rings: 3 Composed of: small rocks and dust Satellites: 8Names: Nereid, Proteus, & Triton Satellites: 8Names: Nereid, Proteus, & Triton Slide 45 Slide 46 Pluto Pluto was found by the American astronomer Clyde W. Tombaugh in 1930. Pluto was found by the American astronomer Clyde W. Tombaugh in 1930. Occasionally, Neptunes orbit is actually outside that of Pluto; this is because of Pluto's highly eccentric (non- circular) orbit. During this time (20 years out of every 248 Earth years), Neptune is actually the farthest planet from the Sun (and not Pluto). Occasionally, Neptunes orbit is actually outside that of Pluto; this is because of Pluto's highly eccentric (non- circular) orbit. During this time (20 years out of every 248 Earth years), Neptune is actually the farthest planet from the Sun (and not Pluto). Slide 47 Distance from the Sun: 39.53 AU Distance from the Sun: 39.53 AU Rotation: 6.39 Earth Days Rotation: 6.39 Earth Days Revolution: 247.7 Earth Years Revolution: 247.7 Earth Years Diameter: 2,274 km (1,413 mi) Diameter: 2,274 km (1,413 mi) 1/5 the diameter of the Earth Atmosphere: probably mostly nitrogen with a little carbon monoxide and methane Atmosphere: probably mostly nitrogen with a little carbon monoxide and methane Surface Conditions: It is probably made up of about 70% rock and 30% water. Surface Conditions: It is probably made up of about 70% rock and 30% water. Temperature: -396F to -378F (-238C to -228C) Temperature: -396F to -378F (-238C to -228C) Life: Not that we know of, too cold. Life: Not that we know of, too cold. Rings: No Rings: No Satellites: 1 Name: Charon Satellites: 1 Name: Charon Slide 48 Plutos atmosphere is definitely not breathable by humans. The atmosphere forms when Pluto is closest to the Sun and the frozen methane is vaporized by the solar heat. When it is farther from the Sun, the methane freezes again. Plutos atmosphere is definitely not breathable by humans. The atmosphere forms when Pluto is closest to the Sun and the frozen methane is vaporized by the solar heat. When it is farther from the Sun, the methane freezes again. Pluto's unusual orbit makes some scientists think that Pluto is not a regular planet. but a "minor planet" Pluto's unusual orbit makes some scientists think that Pluto is not a regular planet. but a "minor planet" A mission was launched in January 2006 to send a spacecraft to Pluto in order to gather further information. A mission was launched in January 2006 to send a spacecraft to Pluto in order to gather further information. Slide 49 Slide 50 Planetary Tilt Slide 51 Planetary Distances Mercury 0.4 AU Mercury 0.4 AU Venus 0.7 AU Venus 0.7 AU Earth 1.0 AU Earth 1.0 AU Mars 1.5 AU Mars 1.5 AU Jupiter 5.0 AU Jupiter 5.0 AU Saturn 10.0 AU Saturn 10.0 AU Uranus 19.0 AU Uranus 19.0 AU Neptune 30.0 AU Neptune 30.0 AU Pluto 39.0 AU Pluto 39.0 AU Light travels through space at 300,000-km/s. Light travels through space at 300,000-km/s. So it takes about 8 minutes for light from the sun to travel 1 AU and reach us. So it takes about 8 minutes for light from the sun to travel 1 AU and reach us. How long would it take light from the sun to reach Pluto? How long would it take light from the sun to reach Pluto? 39 x 8 = 312 minutes, or 5.2 hours! 39 x 8 = 312 minutes, or 5.2 hours! Slide 52 Solar System Project You will be divided into 9 groups You will be divided into 9 groups Each group will be assigned a planet to research Each group will be assigned a planet to research Groups will create a poster, including facts about your planet and drawings or pictures Groups will create a poster, including facts about your planet and drawings or pictures Each group will present their planetary research to the class Each group will present their planetary research to the class Using the research from each group, every student will create a book of the planets Using the research from each group, every student will create a book of the planets Slide 53 Research Requirements Use at least 3 sources, including books, encyclopedias, and Internet Use at least 3 sources, including books, encyclopedias, and Internet Compare/Contrast Planets Compare/Contrast Planets Size relative to earth Size relative to earth Surface Features Surface Features Atmospheric Features Atmospheric Features Relative Distance from Sun Relative Distance from Sun Ability to Support Life Ability to Support Life Slide 54 Slide 55 Comets, Asteroids, and Meteors Slide 56 Comets Comets are chunks of ice and dust whose orbits are very long, narrow ellipses. Comets are chunks of ice and dust whose orbits are very long, narrow ellipses. Often thought of as dirty snowballs. Often thought of as dirty snowballs. Slide 57 Comet Orbits Most comets are on very eccentric orbits that seldom pass near the Earth. Most comets are on very eccentric orbits that seldom pass near the Earth. Slide 58 Comet Structure Nucleus: main solid core of the comet. Nucleus: main solid core of the comet. Tail: gas and dust particles released by the comet. They are pushed by the solar wind away from the sun. Tail: gas and dust particles released by the comet. They are pushed by the solar wind away from the sun. Coma: gases and dust released by the comet when energy from the sun heats the comet and causes the solid materials to turn into a gas. Coma: gases and dust released by the comet when energy from the sun heats the comet and causes the solid materials to turn into a gas. Slide 59 Periodic Comets Comets that repeatedly orbit into the inner solar system are periodic comets. Comets that repeatedly orbit into the inner solar system are periodic comets. Comet Halley is a famous, short period comet. It appears every 76 or so years. Comet Halley is a famous, short period comet. It appears every 76 or so years. Nucleus of Halleys comet taken by the Giotto spacecraft. Nucleus of Halleys comet taken by the Giotto spacecraft. Slide 60 Halleys Comet Last appeared in 1985-86. Should appear again in 2061. Last appeared in 1985-86. Should appear again in 2061. Like most comets it has a very eccentric orbit. Like most comets it has a very eccentric orbit. Slide 61 Comet Clouds Most comets are from one of two clusters, the Kuiper Belt and the Oort Cloud. Most comets are from one of two clusters, the Kuiper Belt and the Oort Cloud. The Kuipier Belt is close to Pluto, from 30 to 50 AU from the sun. The Kuipier Belt is close to Pluto, from 30 to 50 AU from the sun. The Oort Cloud is material left over from the formation of the solar system and is more than 100,000 AU from the sun. The Oort Cloud is material left over from the formation of the solar system and is more than 100,000 AU from the sun. Slide 62 Asteroids Asteroids are rocky or metallic objects, most of which orbit the Sun in the asteroid belt between Mars and Jupiter. A few asteroids approach the Sun more closely. None of the asteroids have atmospheres. Asteroids are rocky or metallic objects, most of which orbit the Sun in the asteroid belt between Mars and Jupiter. A few asteroids approach the Sun more closely. None of the asteroids have atmospheres. Asteroids are also known as planetoids or minor planets. Asteroids are also known as planetoids or minor planets. Slide 63 Asteroid Belt The asteroid belt is a doughnut-shaped concentration of asteroids orbiting the Sun between the orbits of Mars and Jupiter, closer to the orbit of Mars. The asteroid belt is a doughnut-shaped concentration of asteroids orbiting the Sun between the orbits of Mars and Jupiter, closer to the orbit of Mars. Most asteroids orbit from between 186 million to 370 million miles (300 million to 600 million km or 2 to 4 AU) from the Sun. Most asteroids orbit from between 186 million to 370 million miles (300 million to 600 million km or 2 to 4 AU) from the Sun. The asteroids in the asteroid belt have a slightly elliptical orbit. The time for one revolution around the Sun varies from about three to six Earth years. The asteroids in the asteroid belt have a slightly elliptical orbit. The time for one revolution around the Sun varies from about three to six Earth years. Slide 64 Number of Asteroids There are about 40,000 known asteroids that are over 0.5 miles (1 km) in diameter in the asteroid belt. There are about 40,000 known asteroids that are over 0.5 miles (1 km) in diameter in the asteroid belt. About 3,000 asteroids have been cataloged. There are many more smaller asteroids. About 3,000 asteroids have been cataloged. There are many more smaller asteroids. The first one discovered (and the biggest) is named Ceres; it was discovered in 1801. The first one discovered (and the biggest) is named Ceres; it was discovered in 1801. Slide 65 Asteroid Size Asteroids range in size from tiny pebbles to about 578 miles (930 kilometers) in diameter (Ceres). Asteroids range in size from tiny pebbles to about 578 miles (930 kilometers) in diameter (Ceres). Sixteen of the 3,000 known asteroids are over 150 miles (240 km) in diameter. Sixteen of the 3,000 known asteroids are over 150 miles (240 km) in diameter. Some asteroids even have orbiting moons. Some asteroids even have orbiting moons. Slide 66 Origin of the Asteroid Belt The asteroid belt may be material that never coalesced into a planet, perhaps because its mass was too small. The asteroid belt may be material that never coalesced into a planet, perhaps because its mass was too small. The total mass of all the asteroids is only a small fraction of that of our Moon (about 1/30 th ). The total mass of all the asteroids is only a small fraction of that of our Moon (about 1/30 th ). A less satisfactory explanation of the origin of the asteroid belt is that it may have once been a planet that was fragmented by a collision with a huge comet. A less satisfactory explanation of the origin of the asteroid belt is that it may have once been a planet that was fragmented by a collision with a huge comet. Slide 67 Near-Earth Asteroids Asteroids whose orbits bring them within 1.3 AU of the Sun are called Near-Earth Asteroids (NEA) or Earth- Approaching asteroids. Asteroids whose orbits bring them within 1.3 AU of the Sun are called Near-Earth Asteroids (NEA) or Earth- Approaching asteroids. These asteroids probably came from the main asteroid belt, but were jolted from the belt by collisions or by interactions with other objects' gravitational fields (primarily Jupiter). These asteroids probably came from the main asteroid belt, but were jolted from the belt by collisions or by interactions with other objects' gravitational fields (primarily Jupiter). Slide 68 NEA Concerns About 250 NEAs have been found so far, but many, many more exist. About 250 NEAs have been found so far, but many, many more exist. The largest known NEA is 1036 Ganymede, with a diameter of 25.5 miles (41 kilometers). The largest known NEA is 1036 Ganymede, with a diameter of 25.5 miles (41 kilometers). According to astronomers there are at least 1,000 NEA's whose diameter is greater than 0.6 miles (1 kilometer) and which could do catastrophic damage to the Earth. According to astronomers there are at least 1,000 NEA's whose diameter is greater than 0.6 miles (1 kilometer) and which could do catastrophic damage to the Earth. Even smaller NEA's could cause substantial destruction if they were to collide with the Earth. Even smaller NEA's could cause substantial destruction if they were to collide with the Earth. Slide 69 Demise of the Dinosaurs? An asteroid impact with the Earth may have caused the extinction of the dinosaurs. An asteroid impact with the Earth may have caused the extinction of the dinosaurs. The Alvarez Asteroid Theory explains the huge K-T mass extinction 65 million years ago by a large asteroid hitting the Earth off the Mexican Yucatan peninsula. The Alvarez Asteroid Theory explains the huge K-T mass extinction 65 million years ago by a large asteroid hitting the Earth off the Mexican Yucatan peninsula. This impact would have caused severe climactic changes leading to the demise of many groups of organisms, including non-avian dinosaurs. This impact would have caused severe climactic changes leading to the demise of many groups of organisms, including non-avian dinosaurs. Slide 70 Meteoroids Meteoroids are small chunks of dust and rock in space. Meteoroids are small chunks of dust and rock in space. Usually come from comets or asteroids. Usually come from comets or asteroids. Slide 71 Meteors When a meteoroid enters the Earths atmosphere friction will cause it to heat up. When a meteoroid enters the Earths atmosphere friction will cause it to heat up. It will leave a bright streak of light across the sky as it burns up. It will leave a bright streak of light across the sky as it burns up. Are called meteors when they brightly fall to the Earth. Are called meteors when they brightly fall to the Earth. Often occur in showers, with several sightings a minute. Often occur in showers, with several sightings a minute. Slide 72 Meteorites While the vast majority of meteors burn completely up, ones that are large enough pass through the atmosphere and hit the surface. While the vast majority of meteors burn completely up, ones that are large enough pass through the atmosphere and hit the surface. Most look like stones, so they are not noticed. Some are easy to identify as they are made of iron or nickel. Most look like stones, so they are not noticed. Some are easy to identify as they are made of iron or nickel. Slide 73 Craters Meteorites create craters when they strike the surface of a planet. Meteorites create craters when they strike the surface of a planet. Our moon is covered with craters caused by meteorites, asteroids, and comets. Our moon is covered with craters caused by meteorites, asteroids, and comets. Meteor Crater in Arizona is a famous crater found in the USA. Occurred 50,000 years ago. Meteor Crater in Arizona is a famous crater found in the USA. Occurred 50,000 years ago. Hit with the force of 150 Hiroshima A bombs. Hit with the force of 150 Hiroshima A bombs.