WC9 - Recap Our Solar System (I) What sky observations are...

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Unformatted text preview: Recap Our Solar System (I) What sky observations are used to build a calendar ? How do you explain the changing shape of the Moon ? What is the reason for having seasons on Earth ? What are the main characteristics of Earth, which distinguish it from other planets in our solar system? Explain why Earth has so much atmospheric oxygen. Which is the hottest layer in Earth's atmosphere ? How do you explain auroras ? Recap Our Solar System (II) What are the main differences between Earth and Moon ? Explain two phenomena which relate to the EarthMoon system. Name the 3 groups of planets in our solar system Name the most important characteristics of Mercury, Venus, Mars. Giant Planets: Jupiter Jupiter, with a radius about 11 times that of Earth, is about 2.5 times larger than all other planets put together. Its density, a quarter of Earth density, is similar to that of the Sun and so is its composition. Revolution of 11.86 years, and a full spin in about 10 hours. Layered structure (going towards its center): Winds of 540km/h the Great Red Spot is a highpressure system with color due to phosphorus. Huge magnetic fields extending to 4 7 millions km produce auroras 100,000 brighter than on Earth. 1000km of hydrogen atmosphere (but also, ammonia ice and water ice) 20,000km of liquid molecular hydrogen (no solid surface) 40,000km of liquid ionized hydrogen 10,000km of rockymetallic core. Temperature at the center about 20,000oC. Jupiter Jupiter Signature: The largest planet in the solar system Hydrogen based structure Jupiter's Moons Jupiter has 16 moons and a faint system of rings of particles of dust, which were blasted off the moons by meteor impact. 12 moons are small (R=5130km) while 4 are comparable with our Moon and were discovered by Galileo in 1610. In increasing distance from Jupiter: Io, Europa, Ganymede and Callisto. Io and Europa have a density similar to our Moon Ganymede and Callisto have lower densities, due to a lot of ice. Callisto and Europa might have a liquid subsurface ocean with some elementary forms of life. Ganymede might have a metallic core Io has a lot of volcanic activity. Jupiter's Moons Europa Io Giant Planets: Saturn Saturn has a radius 9 times larger than Earth, revolution=29.5 years, spin=10 hours and 39 minutes. It has about half of Jupiter's density (the least dense among planets). Its structure has: A core with R=12,000km with rocks, metals 17,000km of liquid ionized hydrogen 30,000km of liquid molecular hydrogen Hydrogen atmosphere, magnetic field, high winds (up to 1500km/h), storms Saturn was investigated by Pioneer 11 in 1979, Voyager in 1980/81 and by Cassini in August 2004. Saturn Saturn Signature: The rings expanding 1 lightsec. from the planet Saturn's Rings and Moons Saturn's 3 rings expanding almost 1 lightsecond from surface (some faint rings extend to 1.5 light seconds) but with a vertical thickness of only 150m. They contain ice and icecoated rock particles of up to tens of meters in size. As Saturn moves around the Sun the aspect of rings seen from Earth changes. Saturn also has at least 18 moons most are small, 4 are medium size and one (Titan) is larger than Mercury. Titan is quite unique as it has an atmosphere with 9--95% nitrogen and 5% methane. This atmosphere with a density twice higher than on Earth has hydrocarbons. But at 178oC liquid methane may exist only under a crust of solid methane. Cassini investigated this moon at the end of 2004. Saturn's Titan Giant Planets: Uranus Uranus is the first planet discovered with a telescope in 1781. Its radius is 4 times that of Earth, revolution=84 years, spin=17 hours. Its axis is tilt at 98o which makes one season 42 years long; when Voyager 2 flew past Uranus in 1986 its South pole was facing the Sun; North pole will face the Sun in 2030. Its atmosphere with 83% H, 15% He and 2% methane, which absorbs red light making the planet look greenblue. Its structure: Surface temperature is 215oC and weak magnetic field. Uranus has at least 10 narrow dark rings and 15 moons. 25% core of rocks and metals 60% middle ocean of ionized ice 15% dense hydrogen layer. Uranus Uranus Signature: Its greenblue color due to atmospheric methane Neptune was discovered in 1846. Its radius is 4 times that of Earth, revolution=164.8 years and spin=16 hours. Density 20% higher than Earth. Atmosphere similar to Uranus: 80% H, 19% He and methane 12%. In 1989 it had a "Great Dark Spot" which disappeared. Like Jupiter and Saturn, Neptune radiates more energy than it receives from the Sun (hot interior). Like with Uranus, its magnetic field is generated in the icerich envelope. Neptune has 5 faint rings and 8 moons. Triton (R=1350km) is the largest moon with 80% reflectivity and with T=236oC was the coldest body investigated by a spacecraft (Voyager 2). Polar caps with nitrogen ice and geysers of hydrocarbonrich material. Triton moves in a direction opposite to Neptune's spin and will probably break. Giant Planets: Neptune Neptune and Triton Neptune Triton Neptune Signature: Similar to Uranus The system with Triton Pluto Discovered in 1930, following speculations related to the study of Uranus. Smaller than our Moon (R=1650km), revolution=248 years, spin=6.387days, tilt=17 degrees. Structure of rock and ice; polar nitrogen and methane ice. Its large moon, Charon, rotates around Pluto and spins in 6.387 days, showing the same hemisphere to each other. Pluto is probably part of the "Kuiper belt" of icerich objects that populate the outer regions of the solar system. Pluto Pluto Signature: Until recently, the most remote solar planet Asteroids(I) Asteroids, or "small planets", are small cosmic bodies with a radius below 500 km which revolve around our Sun. The first, Ceres, was discovered in 1801 and is the largest (R=470km). Today we know over 4000 asteroids, most of them of irregular shapes. The main belt is between Mars and Jupiter. "The Trojans" are two groups on the same orbit as Jupiter (60 degrees before and after the planet). "The Centaurs" are a group between the orbits of Saturn and Neptune; this group together with Pluto are part of the larger "Kuiper belt" that surrounds our planetary system. 3 groups (Atens, Amors and Appolos) are close to Earth and about 2000 asteroids (with a radius over 500m) closely approach the orbit of Earth. Asteroids (II) Telescopes see asteroids as tiny points of light, but spectral analysis and radar showed that different groups have different properties. First close look by Galileo spacecraft in 1991 (Gaspra seen from 1,600 km) Most astronomers believe that asteroids were debris left when planets were formed 4.5 billion years ago. In the main belt some are outer Ctype (carbonrich compounds), inner Stype (silicaceous) and Mtype (metallic). Kuiper belt has icerich asteroids. Comets Comets , with their bright fuzzy head and a long tail, are a dramatic spectacle. Edmund Hailey was the first to establish their origin. His comet made the most recent return in 1986. Comets are of shortperiod (under 200 years orbital period) or longperiod type. Composition: Their nucleus is a fluffy lump of ice a few kms wide. Near the Sun it evaporates, but being rich in carbon it emits jets of dust and gas. UV radiation ionizes atoms and the solar wind accelerates these ions. When electrons are recaptured atoms reemit light as a type 1 tail. Sunlight also propels small particles of dust out of the head and these are the type 2 tail. The tail can be very long (twice than the distance EarthSun). Meteoroids Meteoroids are small interplanetary particles of size between micrometer and meter. They go through thermosphere at high speeds and disintegrate producing traces of ions which produce shortlived trails of light, called meteors ("shooting stars"). A typical nakedeye meteoroid is visible around 110km and burns by 75km altitude. Most of meteors have densities lower than water. They can be sporadic or shower. Some come from comets (ex. the Leonid shower). Meteorites Meteorites are larger than meteoroids and after plunging through the atmosphere they reach the ground. They form a fireball, that can be brighter than Moon or even the Sun. Classes: stony, stonyiron and iron Impact craters: West Australia, Namibia, Arizona, equivalent to nuclear explosions. 1908 Tunguska small asteroid or comet nucleus. Most meteorites are 4.55 billion years old. Some originated from our Moon or Mars. ...
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This note was uploaded on 05/03/2011 for the course NATS 1740 taught by Professor Hall during the Spring '10 term at York University.

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