Unit 2 Astro (1)

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Pennsylvania State University *

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Astronomy

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Oct 30, 2023

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KEPLER’S LAWS Heliocentric Model - Sun treated as center of universe - Replaced the geocentric model - Advocated earth as the center of universe The planet revolves around the Sun in an elliptical orbit - No center First Law - Planets orbit around the sun not in circular orbits, but along orbits that are elliptical in shape, with the sun at one of the foci of the ellipse - Goes faster when close to the sun 2nd Law - Perihelion - The point in its orbit where the planet is closest to the sun - Planet is the fastest - Aphelion - The point in orbit where it’s farthest away from the sun - Planet is the slowest 3rd Law - Unifying factors between the motions of planets along various orbits - Orbital period =P(in earth days) - Average distance of planet from the sun -semimajor axis =a(in km) - P^2=a^3 Quiz Questions - What was Kepler's first law? - Planets revolve around the sun in elliptical orbits with the sun at one focus of the ellipse - What best describes the orbit of earth around the sun? - An ellipse that is close to being circular - Which of the following does Kepler’s Second Law support? - When a planet is closer to the sun, it’s speed is greater than when it is farther away - How did Kepler himself originally state this second law? - A line joining a planet and the sun sweepers out equal areas in equal intervals of time - What was Kepler’s Third Law?

- The square of the time period for an orbit of a planet is proportional to its average distance from the sun (in other words P^2 is proportional to a^3) - Saturn is about 10 times as far from the sun as Earth (a=10au). About how many times does the Earth orbit the Sun in the time it takes Saturn to orbit just once? - About 30 JUPITER’S MOON 4 moons - The dots changes position - Some of the moon move quickly than the others - “Galilean Satellites” - Io,Europa,Ganymede, Callisto Galileo and his findings - Controversial - Indicated earth is not the center of universe - Conﬂict of catholic church teachings Io - The strong gravity squeezes it and heats interior - A lot of volcanoes - p=1.8 a=433,000 Europa - Icy surface - Cracks and fractures caused by the icy layer that moves across ocean - P=3.6, a=697,000 Ganymede - Largest moon in the solar system - p=7.1 a=1,093,000 Callisto - Static ball of ice - P=16.7, A=1,923,000 Quiz Questions

- Besides the discovery that moons orbit Jupiter, what other discovery made by Galileo Galilei, with an early telescope, proved the earth is not at the center of the universe? - The phases of venus - Of the four Galilean moons, which is closest to jupiter? - Io - Which moon of Jupiter is believed to have a liquid ocean beneath a layer of ice? - Europa - Which moon of Jupiter is the largest? - Ganymede INNER SOLAR SYSTEM Density - mass/volume Mercury - Closest to the sun - Ranges from -290 to 800 degrees fahrenheit - No atmosphere to retain heat - daytime=hot, nighttime=cold - Much like earth's moon (slightly bigger) - Smallest in solar system - Rough surface - Fastest planet in solar system - 88 days = 1 year - But one day is 176 times as long as a day on earth - Rotates slow - No atmosphere (thin) - Can’t breathe there - Sunlight isn’t scattered to make a blue sky - Has no moons Venus - The hottest planet - Dense atmosphere - Carbon dioxide

- Very extreme - 880 degrees fahrenheit - Hot, cloud earth twin - Rocky, metallic surface like mercury - Volcanoes are continuously active - 85% covered with volcanic rock - Second brightest object after moon - One day=243 earth days - One year=225 earth days - Very slight tilt - No seasons - Closest to Earth Domes - Pancake domes - Flat tops and steep sides,formed by lava - Tick Domes - Odd volcanoes radiating spurs that make them look like their blood feeding namesake - Tesserae - Terrain with intricate patterns of ridges and grooves that suggest the scorching temp makes rock behave in some ways more like peanut butter beneath a thin and strong chocolate layer Quiz Questions - Which of the following statements can be said about venus - Venus has a very slow speed of rotation and venus is closer to the sun than earth is - Which among the following scenarios will be true for someone watching the sky from the venus surface? - The sun would rise in the west and set in the east - Craters on Venus - Are much larger in size than those on Earth, Moon, and Mars - Volcanoes on Venus - Produce very large lava ﬂows that cover at least 85% of the planets surface Earth - 5th largest planet in solar system - day=23.9 hours, year=365.25 days

- Takes 8 mins for sunlight to reach planet - Tilted 23.4 degrees - 4 main layers - Inner core at center - Outer core - Mantle - Crust Quiz Questions - Where do mountains on earth come from - In some locations, plates of rock on the planet’s surface press together and the plates rise together - From what was described, where are aurorae likely to be seen most frequently - At locations near the poles - What is not true about earth's atmosphere - It has more carbon dioxide than venus, so is heated more than venus by the Greenhouse e±ect - What is ozone? - Three oxygen atoms bonded together into a single molecule - What would happen if the ozone layer were completely destroyed? - Ultraviolet radiation from the sun would get through the atmosphere and cause damage to life Greenhouse E±ect - A natural process which made life on Earth possible - Water vapor, carbon dioxide, methane, nitrous oxide-greenhouse gasses The Moon - Brightest and largest object in night sky - Has a core, mantle, and crust Light Areas - Highlands Dark Areas - Maria (seas) - Craters filled with lava 1-4 bil years ago Mars - Dry, rocky, and cold - Half the size of earth

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