Download Study Guide - Experience Astronomy

Experience Astronomy
Study Guide for the Midterm The Purpose of Astronomy Astrology is focused the meanings of heavenly movements (predicting what will happen here on Earth, impacting things on Earth, or in:luencing our personality). Astronomy, however, is a scienti:ic study of the sky. The :irst chapter of Genesis says God created the stars for very practical reasons: • to give us light on the Earth • to separate day from night • to help us create calendars that guide our different seasons of planting, harvesting, and celebrating, and to help us mark different years so we could keep records of history • to help us use the signs in the sky to navigate around and :ind our way The Celestial Sphere Celestial Sphere – a spherical representation or map of the :ixed stars we see in the sky; divided into 88 regions called constellations Celestial Poles -­‐ the axis of the Earth points at these northernmost and southernmost points on the celestial sphere Celestial Equator -­‐ if the Earth’s equator was projected out into space, the line it would make on the celestial sphere is the celestial equator Ecliptic -­‐ the path the sun takes through the celestial sphere over the course of a whole year; it is tilted in respect to the celestial equator because the Earth’s axis is tilted 23.5° The Direction of Spin -­‐ Looking down on the north pole, the Earth spins counterclockwise. Looking straight on at the Earth, it spins in an Eastward direction. This means the celestial sphere overhead moves in a westward direction from our perspective on Earth. Latitude Lines -­‐ a geographic coordinate that indicates the north-­‐south position of a point on the Earth, ranging from 0° at the Equator to 90° at the North and South poles; your latitude position determines what part of the celestial sphere you see (for instance, standing at 90°N, the north pole, means the North Celestial Pole will be at your zenith) 1
Terms Absolute Magnitude -­‐ how bright a star really is if all stars were the same distance from us A.M. -­‐ Ante Meridiem, meaning before the middle of the day Apparent Magnitude -­‐ how bright a star appears in our sky The Arctic Circle -­‐ the latitude line where the sun doesn’t set on the summer solstice Autumnal (Fall) and Vernal (Spring) Equinoxes -­‐ the two days of the year when the sun rises and sets on the celestial equator, making an equal amount of daylight and nighttime Axis -­‐ the line around with the Earth (or any planetary body) rotates Day -­‐ the amount of time it takes for the Earth to spin on its own axis one time The Galilean Moons -­‐ four largest moons of Jupiter: Europa, Io, Callisto, and Ganymede Geocentric Model – a model or understanding of the universe where the Earth is at the center, and the sun, moon, planets and stars revolve around the Earth Horizon – from your perspective, the place where the sky meets the land Jupiter -­‐ a planet named after king god of the Romans; the most massive, fastest spinning planet in the solar system, with more moons than any other planet The Land of the Midnight Sun -­‐ a name for the region north of the Arctic circle because the sun doesn’t set during the summer months Light Year – the distance light travels in a year (about 5.8 trillion miles) Meridian -­‐ the line on the celestial sphere going from due south, straight over your head through the zenith, to due north; it means “middle of the day” The Milky Way -­‐ a cloudy band circling the celestial sphere which is actually about 100 billion distant stars in our Milky Way Galaxy Planet -­‐ a word meaning “wandering star”; the :ive classical planets are Mercury, Venus, Mars, Jupiter, and Saturn P.M. -­‐ Post Meridiem, meaning after the middle of the day Polar Night -­‐ the phenomenon where the sun doesn’t rise north of the Arctic circle during the winter months 2
Retrograde motion -­‐ when a planet stops going eastward against the background stars, turns around, and starts moving westward Saturn -­‐ a planet named after the Roman god of agriculture and wealth; known for its rings Summer solstice -­‐ from the perspective of the Northern hemisphere, the day of the year when the Sun rises and sets at the northernmost place on the horizon, making a large arc through the sky (the day with the most amount of sunlight) Terminator -­‐ the line on the surface of the globe where the night side of the Earth meets the day side Titan -­‐ the largest moon of Saturn, known for its atmosphere and liquid lakes The Tropic of Cancer -­‐ the latitude line where the sun is at the zenith at high noon on the summer solstice The Tropic of Capricorn -­‐ the latitude line where the sun is at the zenith at high noon on the winter solstice The Tropics -­‐ The region between the Tropic of Cancer and the Tropic of Capricorn Winter solstice -­‐ from the perspective of the Northern hemisphere, the day of the year when the Sun rises and sets at the southernmost place on the horizon, making a shallow arc through the sky (the day with the least amount of sunlight) Zenith – from your perspective, the part of the celestial sphere that is right over your head People Aristotle • one of the most famous philosophers of all time • argued for a spherical shape to the Earth • argued for a geocentric model to the universe Aristarchus • :irst person we know about who proposed a heliocentric model of the universe Ptolemy • Greek astronomer • created a catalogue of 48 constellations which much later became the basis for our 88 constellations • followed a geocentric model, creating a mathematical system for predicting the movements of the planets and the stars 3
Copernicus • resurrected the idea of a sun-­‐centered model in the middle ages Kepler • discovered the three laws of planetary motion Galileo • one of the :irst to use a telescope to observe the sky • discovered the four largest moons of Jupiter Constellations and Stars Polaris -­‐ meaning “pole star”; this star in Ursa Minor is commonly called the North Star The Zodiac -­‐ 12 traditional constellations that touch the ecliptic: Aries, Taurus, Gemini, Cancer, Leo, Virgo, Libra, Scorpius, Sagittarius, Capricornus, Aquarius, and Pisces The Summer Triangle -­‐ an asterism made up of the three very bright stars Vega, Deneb, and Altair Fomalhaut -­‐ meaning “mouth of the :ish”; a 1st magnitude star in Pisces Austrinus Pollux and Castor -­‐ two bright stars in the constellation Gemini Aldebaran -­‐ a 1st magnitude star in the constellation Taurus Betelgeuse and Rigel -­‐ two 1st magnitude stars in the constellation Orion Aquila the eagle 4
Lyra the lyre Cygnus the swan 5
Hercules Pisces Austrinus the southern =ish Aquarius the Water Bearer 6
Pisces the =ish Pegasus the =lying horse Andromeda 7
Perseus Cassiopeia Gemini the twins
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Ursa Major the big bear Taurus the bull 9
Aries the ram Capricornus the sea-­‐goat Orion the hunter
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