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Final

FINAL EXAM CH 8 Discoveries about the Solar System.docx

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Department
Natural Science
Course Code
NATS 1745
Professor
Robin Metcalfe

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FINALEXAM CH 8 DISCOVERIESABOUT THE SOLAR SYSTEM The Discovery of Uranus 1. Begins in late 17 century (1800s) -century after Newton constructed first successful reflecting telescope -in era where telescopes getting bigger and bigger allowing astronomers to detect fainter and fainter celestial bodies -known celestial bodies prior to this point consisted of what we could see with naked eye -Galileo first person to change that in 1600s b/c he discovered Jupiter’s moons -nearly century after Galileo’s death, nothing new in sky was discovered until German musician William Herschel -William Herschel (1738-1822) was an amateur astronomer who built the largest telescopes of his time -Astronomy at this time was expensive hobby; to purchase a telescope was extremely expensive -Herschel made his own telescopes 2. While cataloguing stars to aid the search for stellar parallax (and therefore the 1 stellar distances), he became the 1 person to discover a planet -Why did he build these telescopes? Wanted to detect the parallax of stars -In Herschel’s time stellar parallax still hadn’t be detected -Many astronomers were trying to use larger and larger telescopes to try to detect this -Stellar parallax so important to find because it could be used to calculate a star’s distance -distance would reveal how big our universe is -doesn’t detect parallax but finds a planet -ends his financial struggles; King hires him as his personal astronomer and builds largest telescope in world -Sister, who was assistant, also discovered celestial bodies and galaxies and was first female paid scientist 3. March 1781: he observed a star-like object which increased in size when he increased his telescope magnification -knew this was a planet because regardless of how much we increase magnification, stars will still remain pin-point looking -stars do not appear to grow larger 4. Shortly after, he observed its motion relative to the stars -found that object moved from night to night relative to the stars -concluded that this was a comet b/c this is appearance of comets before getting too close to sun to develop and tail -didn’t even consider that what he was looking at was a planet 5. Further investigation revealed its near-circular orbit at ~20AU from the Sun (orbital period = 84 years) -Twice as far from Sun as Saturn; doubled the size of the universe 6. It was accepted as a new planet and named Uranus (Greek god of the sky, father of Saturn, grandfather of Jupiter) -Circular orbit would make it a planet -Elliptical orbit would make it a comet -Planet was tracked by England’s Royal Society and after a few years was declared a planet 7. He also discovered Uranus’2 brightest moons, Titania & Oberon -know today Uranus has 27 moons but Herschel was able to discover two brightest -though Uranus are much bigger than the Earth, it’s moons are much smaller than ours 8. The moon orbits revealed Uranus’mass: 15x Earth’s mass -not as large as Jupiter or Saturn in mass, but still a massive planet 9. Its mass/size = low density, therefore a gas giant (but mostly frozen; also known as an “ice giant”) -today can understand what a planet is made of by studying its light spectrum -each planet has small (compared to rest of planet; however these cores are larger than Earth) solid core of rock, surrounded by hydrogen gas, which composes most of planets mass -In case of Uranus, its solid core seems to be surrounded by frozen gas particles; Uranus is partially gracious and partially frozen 10. By 1979, it was known that Jupiter, Saturn and Uranus have rings -showed for first time Saturn was not only planet with rings -two years later Jupiter’s rings were discovered -Saturn’s rings were the brightest -planetary rings are composes of zillions of rocky particles (believed to be left over from birth of Solar system) and are therefore very grainy 11. Unlike the other planets, Uranus’orbits the Sun on its side, possibly due to a past collision -most planets have tilt which is straight up and down; no tilt greater than 30 degrees -Uranus has a tilt of nearly 90 degrees; planet is practically orbiting the sun on its side -Planet’s equator is perpendicular to its orbit around the sun -Does Uranus therefore have seasons? -Uranus does have seasons; has four -seasonal changes are extreme; Northern Summer will last roughly 20 years and will experience eternal day time for these 20 yrs -for other 20 yrs will have eternal winter and therefore 20 yrs of darkness -all other planets have moderate seasonal changes -believed that this tilt is a result of how our solar system was born; th Wednesday, January 9 , 2013 1. 1801: Piazzi detected a star-like object in a near-circular orbit around the sun at 2.7AU (near Bode’s number after Mars) a. Described the object as being a faint light and thought it to be a fixed star. As the nights passed he noticed its movement and concluded it wasn’t a fixed star 2. It was named “Ceres” and downgraded from planet to asteroid when it was found to be smaller than the moon a. It was known to be smaller since its relatively close to earth yet it still appeared sma
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