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Download Public Lecture - Our Solar System
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OUR SOLAR SYSTEM James Martin Facebook.com/groups/AstroLSSC Twitter.com/AstroLSSC “It’s time for the human race to enter the solar system.” -Dan Quayle Structure of the Solar System • Our Solar System contains a star, planets, dwarf planets, and other objects! • Orbits of the planets are within a few degrees of each other and move in the same direction around the Sun The Sun • Sun’s energy comes from nuclear fusion within its core • A star’s temperature determines its “color” – Coldest stars are red (as low as ~1,000oF) – Hottest stars are blue (as high as ~62,500oF) – Our Sun’s surface temperature = ~10,000oF Defining a Planet • A planet is defined as a celestial body that: – Orbits the Sun – Is nearly spherical due to its own gravity – Travels along an orbital path free of most debris • Dwarf planets meet the first two conditions only Planet Sizes & Compositions • Inner Planets – Terrestrial planets composed of rocky materials with dense iron cores and high average densities • Outer Planets – Jovian planets composed primarily of lighter elements, such as H and He, with low average densities Mercury • Revolution period of 88 days • Extreme temperature fluctuations ranging from 800oF to -270oF • No moons Venus • Thick CO2, H20 and H2SO4 (sulfuric acid) atmosphere traps sunlight and broils the planet’s surface – Maximum surface temperature reaches up to 900oF • Revolution period of 225 days, but one rotation is 243 days – In other words, 1 day on Venus is longer than 1 year! • No moons Earth • Only planet known to support living organisms • 71% surface is composed of water – Oceans help to maintain stable temperatures • O & Nitrogen rich atmosphere is layered trap sunlight to heat the surface (greenhouse effect) • One Moon orbits Earth Mars • Water on Mars! – Most water is frozen in the polar caps or as subsurface permafrost – Subsurface liquid water recently discovered • Appears red due to iron oxide (rust) in its soil • One revolution takes about 2 yrs • 2 moons orbit the planet Jupiter • Great Red Spot is a complex storm raging for the last ~400 years • Largest and most massive planet – Diameter is 11x bigger than that of Earth’s • One revolution takes about 12 years • Composed mostly of H and He • 67 known moons! Io and Europa over Jupiter disk Saturn • Mostly composed of H and He • Complex ring structure A-G – Only A, B and C rings can be readily seen from Earth! – Rings are less than 1 mile thick, but extend to ~ 260,000 miles from the surface • One revolution takes ~30 years • 62 known moons! Uranus • Bluish color is a result of methane in the atmosphere (absorbs red and green light) • One revolution takes ~84 years • Cloud top temperatures measured to be about -350oF over most of the planet • Planet is tilted 60o and appears to rotate on its side • 5 known moons Neptune • Also blue due to methane in the atmosphere • One revolution takes ~165 years • Several large storm systems similar to Jupiter’s G.R.S. – Great Dark Spot is the size of Earth! • Fastest winds in the solar system (~1200 mph) • 14 known moons Dwarf Planets Video: What is a dwarf planet? Asteroids • Asteroid sizes range from 100m to about 1000km • 100,000+ rocky objects within the orbit of Jupiter (2-3.5 AU) – Orbit the Sun in the same direction as the planets Meteoroids • Interplanetary rocky material smaller than 100m (down to grain size) – Called a meteor as it burns in Earth’s atmosphere – If it makes it to the ground, it is a meteorite • Most meteor showers are the result of the Earth passing through the orbit of a comet which has left debris along its path Trans-Neptunian Objects • 1,000+ small bodies orbiting beyond Neptune in the same direction as the planets – Most are in the Kuiper Belt at 30-50 AU – Pluto orbits at an avg. 39 AU! Comets • Kuiper Belt collisions cause fragmented objects to change orbits • Sun’s radiation vaporizes ices, producing gas and dust tails • Some comets from the Oort Cloud (~50,000 AU) Scale of the Solar System FOR ASTRONOMY NEWS + EVENTS… Facebook.com/groups/AstroLSSC Twitter.com/AstroLSSC LSSC.edu/faculty/james_martin Thank You for Attending!