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Name:______________________ Period:____ Unit 7 Astronomy Focus Questions ___1. How and why do stars move through our sky? ___2. Explain the apparent motion of the Sun through our sky? How does the path of the Sun change throughout the year? ___3. Why do we have seasons? ___4. How does latitude and the angle of the Sun affect daylight hours? ___5. Explain why we see the Moon’s phases? ___6. Explain what happens during a lunar and solar eclipse? ___7. Why do we have tides? ___8. What is the true shape of an orbit and what are the parts of an orbit? What is the equation to measure an orbit’s eccentricity? ___9. Explain what the HR diagram is used for? Explain our Sun’s properties by using the HR diagram. ___10. Describe galaxies and what theory is used to describe the formation of the universe? How can we tell if celestial objects are moving towards or away from us? A. Celestial Observations celestial 1. The objects in the sky collectively are called ____________________ _____________________ objects The Sun, planets, moons, stars, etc. --They include ____________________________________ From East to West --They appear to move in the sky ______________________ An arc --The path they appear to take is in the shape of _______________ 2 2. All objects in the night sky appear to travel in a set path around ____________which is located almost Polaris directly over the North Pole of Earth. Many of the stars form specific patterns, or constellations Some of these never go below the ________________. horizon in New York State. Instead, they appear to circle Polaris over the course of a night. This is about a ten hour time exposure of the northern sky. The arcs are the paths of the stars circling the North Star (Polaris) in the center. These stars can be seen year-round in the northern sky although their exact location each night will vary throughout the year. Orion 3 Other stars appear to move throughout the night from east to west. These are trails of stars that are further to the south in our night sky. Their trails appear almost straight. The constellations and the stars that make them up also appear in different locations throughout the year. All celestial objects appear to move at a rate of 15 degrees per hour. (From horizon to horizon is about 180 degrees.) Why do these objects appear to move at a rate of 15 degrees per hour? Because Earth rotates 15 degrees per hour _______________________________________________________ We call this motion the Apparent daily motion _________________________________ 3. Apparent Solar Day: _________________________________ How long it takes the Sun to move _______________________________________ through our sky. 5 B. Terrestrial Observations 1. There are two main motions of Earth: motion of one object around another a. Revolution: The ___________________________________________ ____________________________________________ object. The planets revolve around the Sun. Moons and satellites revolve around planets. Evidence: Different constellations appear in our night sky at different times of the year. b. The spinning of an object on its axis. Earth Rotation: __________________________________________ rotates once every 24hrs. ____________________ Evidence: (1) Foucault’s Pendulum: A mass suspended from a _____________________________ wire at a single _____________________________ point. When set in motion, _____________________________ its apparent change in _____________________________ position is the result of the _______________________ ______ rotation of the Earth. 7 (2) Coriolis Effect: The deflection of ______________________________ a an object that is moving above the Earth’s surface. In the Northern ______________________________ Hemisphere, the Coriolis effect causes moving ______________________________ ______________________________ objects to be deflected to their right, while in the ______________________________ Southern Hemisphere, the deflection is to the object's left. 2. Apparent Motion of the Sun: It changes with the seasons and latitude due to: ________________________ Earth does not lie directly Earth’s Tilt 23 ½ degrees straight up and down, it is tilted _____________ 9 The Sun rises N of Summer: __________________ due East and sets N of due __________________________ West. The noon Sun is highest __________________________ in the sky but the sun ___________ is NEVER directly overhead for us! Because the path of the sun is longest in the summer, days are longest. 10 Occurs approx. on June Summer Solstice: _____________________________ ___________________________________________ 21st The Sun rises S of due East and sets S of Winter: _____________________________________ due West. The noon Sun is lowest in the sky ___________________________________________ Occurs approx. on Winter Solstice: ______________________________ December 22nd. ___________________________________________ Spring and Fall: The Sun rises due East and ______________ ______________ sets due West. The noon Sun ______________ is at approx. 48 degrees. Vernal Equinox: Approx. March 21st ______________ Autumnal Equinox: ______________ Approx. September 22nd At the _______________, day and night are 12 hours long everywhere Equinoxes on Earth. Latitude: The closer you are to the poles, the lower the noon time sun and the greater the difference between the winter and summer length of daylight. At the equator, day and night are 12 hours long all year. Important Note: We do not have summer in June because we are closer to the sun. We are actually closest to the sun in December, the beginning of winter. 11 Tropics of Cancer and Capricorn: 23.5o north and south latitude. Mark the furthest north and south travel of the direct rays of the sun. Sun is directly over the Tropic of Cancer on June 21st and the Tropic of Capricorn on December 21st. 12 Sun’s apparent path for four different observers on June 21st. Notice how the path and position of the noontime sun change for each location. Because the sun is higher in the sky in the summer, the rays of the sun shine down at a more direct angle. The length of shadows cast by a stick are also affected by the height of the sun. In the summer, the sun is high in the sky, so the short shadows it casts are ______. Shadows cast in longer spring and fall are __________. In the winter, the sun is very low in the sky, so the shadow it long casts is very ____. C. Geometry of Orbits I. Terms The motion of one object around another A. Revolution: __________________________ object. Path of movement of a satellite around its primary body. B. Orbit:_______________________________ 1. Example: __________________________ The moon around the Earth. Shape of planet’s orbits around the Sun 2. Ellipse: ___________________________ (flattened or squashed circle). __________________________________________ 3. Focus (foci): _______________________ 13 Ratio of focal length to length of 4. Eccentricity: ___________________________ major axis of an ellipse. (How flat an ellipse is) _________________________________________ a. Formula: ____________ E=d/ ____________ L ____________ ____________ ____________ 14 II. Force and Energy force that keeps all satellites A. Gravity: The __________________________ moving inward in their curved orbits. ________________________________________ The tendency of an object in B. Inertia: ___________________________ motion to continue in motion in a straight ________________________________________ path. C. Energy and Orbits Earth is closest to the Sun; 1. At perihelion: ____________________ pull of gravity is greatest ________________________________________ ________________________________________ Earth is furthest from the 2. At aphelion: _____________________ Sun; pull of gravity is weaker ________________________________________ ________________________________________ 15 III. Orbits and Johannes Kepler A. Orbital Velocity: _____________________ Speed of orbiting object B. Earth’s Orbit 1. perihelion: ________________________ Earth is moving the _________________________________________ fastest Earth is moving the 2. aphelion: _________________________ slowest _________________________________________ 16 C. Kepler’s Laws of Planetary Motion -Johannes Kepler, a German astronomer during the late 1500’s to early 1600’s, developed three laws of motion of objects in the sky to help better explain and predict their motions. Before Kepler, most astronomers agreed that planetary orbits were circular. 1. Elliptical Orbits: ______________________ The orbits of the planets are _________________________________________ ellipses, with the Sun at one focus of the ellipse. The line joining the planet to the 2. Equal Areas: _________________________ Sun sweeps out equal areas in equal times as the _________________________________________ planet travels around the ellipse. 17 ________ Inertia Gravity _________ Orbit 18 Note that as the orbiting body gets closer to the object it is orbiting, the pull of gravity becomes stronger. Therefore, its forward speed must also be greater to compensate. 3. Harmonic Motion: the period for a planet to orbit the Sun increases rapidly with the radius of its orbit The distance between the a. Astronomical Unit: ____________________ Earth and the Sun; 93 million miles. _________________________________________ 19 D. Satellite Motions Earth’s natural satellite The Moon: ____________________________ The moon revolves in its orbit A. Orbit _____________________________ at the same rate that it rotates _________________________________________ I. 1. Sidereal month: ___________________ _________________________________________ The moon takes 27 days to complete _________________________________________ one revolution around Earth. 2. Synodic (lunar) month: _____________ The moon’s phases take about 29 ½ _________________________________________ days to go through one cylce. _________________________________________ 20 (27 1/3 days) One synodic month later (29 ½ days) 21 The apparent change in the shape of the B. Phases: ________________________________ moon caused by the changing positions __________________________________________ of Earth, the Sun, and the Moon. __________________________________________ C. Phases change from: ____________ Waxing to Waning 22 New Moon New Gibbous Third Quarter New Crescent Full Moon Old Crescent First Quarter Old Gibbous D. Because of the moon orbiting Earth, each day the moon rises over the in a different spot eastern horizon ______________ ___________. E. As a result, if you look at the moon two consecutive nights, the moon East is farther ________ the second night and each night thereafter. Day 1 C. Tides: _________________________________ The twice-daily rise and fall of the __________________________________________ oceans due to the gravitational __________________________________________ attraction of the moon and the Sun. 2 highs and 2 lows per day, 1. High and Low: ________________________ every 6 hours __________________________________________ Normal tidal change is less 2. Normal: ______________________________ than 3 feet __________________________________________ NOTE: Even though the sun is much larger, the moon is much closer so the primary force pulling on the tides is the moon. 23 Highest high tides and lowest low 3. Spring:_________________________________ tides, moon phase is near full and new. __________________________________________ Smallest change between high and low 4. Neap: __________________________________ tides, moon is in the quarter phases. __________________________________________ 24 The partial or complete obscuring D. Eclipses: ________________________________ (hiding) of one celestial body by another. __________________________________________ 1. Shadow Geometry Inner, darker part a. umbra: ____________________________ Outer, lighter part b. penumbra: _________________________ __________________________________________ 25 when sun "gets dark" because the 2. Solar Eclipse: __________________________ moon blocks sunlight from reaching the Earth. ________________________________________ Solar Eclipses happen during a New Moon. When the entire Sun is blocked out by the moon a. total: ______________________________ some of the Sun is blocked out b. partial:When ____________________________ c. annular: ___________________________ When the moon is further away from the _______________________________________ Earth and you see an orange ring around the moon. 26 3. Lunar: _________________________________ When the full moon moves into Earth’s __________________________________________ shadow. a. total: ________________________________ When the moon is closer to Earth and the Earth’s __________________________________________ shadow completely covers it. b. partial: ______________________________ When the moon is further from Earth and the Earth’s __________________________________________ shadow partially covers it. NOTE: Lunar eclipse does not occur during every full moon because the plane of the moon’s orbit is slightly off from Earth’s. 27 E. The Solar System I. A star and it’s surrounding planets. Solar System: __________________________ A. Models Model of the solar system with the 1. Geocentric: _________________________ Earth at the center. _________________________________________ The planets revolve around the Sun epicycle: ___________________________ in circular orbits called epicycles. _________________________________________ Retrograde Motion: ___________________ 28 Geocentric Model of the Solar System Problem:_____________________________ Did not explain the Focault ____________________________________ Pendulum and the Coriolis Effect 29 2. First Heliocentric: _______________________ Had circular orbits. _________________________________________ Did not explain the changing size Problem: __________________________________ of the Sun. _________________________________________ Planets move in ellipses. 3. Revised Heliocentric: _____________________ _________________________________________ 30 B. Objects A star that is the basis of the solar system 1. Sun: __________________________________ and that sustains life on Earth, being the source of ____________________________________________ heat and light. Dark, irregular spots that are cooler than a. sunspots: ___________________________ the surrounding areas on the Sun. ___________________________________________ brief powerful eruption of b. flares/prominences: a___________________ particles and intense electromagnetic ____________________________________________ radiation from the sun's surface 10,000-27 mil. Degrees F 31 A celestial body moving in an 2. Planets: _______________________________ elliptical orbit around a star. a. Terrestrial: __________________________ Small, inner planets made up of ____________________________________________ mostly solid rock; high density b. Jovian: _____________________________ Large, outer planets made up of ____________________________________________ mostly gases; low density. 3. Asteroids: ______________________________ A small rocky body orbiting the ____________________________________________ sun. Large numbers of these are found between the orbits of Mars and Jupiter 32 B. Objects (cont.) A meteoroid is a sand- to boulder-sized particle of 4. Meteors: ____________________________ debris in the Solar System. The visible path of a meteoroid that enter _________________________________________ Earth's atmosphere is called a meteor, or a shooting star. If a _________________________________________ meteoroid reaches the ground then it is called a meteorite. _________________________________________ 5. Comets: They are a mixture of ices (both water _________________________________________ and frozen gases) and dust, _________________________________________ Earth “dirty snowballs” _________________________________________ Sun Comet F. The Universe I. Parts of the Universe Objects in space that emit A. Stars: ______________________________ __________________________________________ their own light. create their energy through 1. Energy: Stars __________________________ _________________________________________ the process of nuclear fusion. stars are big exploding balls of 2. Composition: _____________________ _________________________________________ gas, mostly hydrogen and helium. of lines that show the a. spectrum: Pattern _______________________ chemical makeup of a star. _________________________________________ breaks down the light emitted or b. spectroscope: ____________________ __________________________________________ absorbed by chemical elements into specific lines of color. 33 Cloud of gas and dust where new stars Nebula: ______________________________________ are born. _____________________________________________ Star Life Cycle: Stars are like humans. They are born, live and then die.: new, just forming Protostar: _____________ star; baby star _____________________ Mature star:___________ pre-teen Stage ____________ a star with a Red Giant:__________ mass like our Sun that is ___________________ in the last phase of its life _____________ 34 White Dwarf: ______ an old star that has used up _________________ all of its hydrogen. _________________ Very dense. _________________ Supernova: ______ The explosive death ________________ of a massive star whose ________________ energy output causes its expanding gases to glow ________________ brightly ________________ 36 The life cycle of stars depends on their mass. Small and medium stars become black dwarves once they die. Neutron Stars Larger stars become novae and die as: ____________ Black Holes The most massive stars become supernovae and die as: ______________ Star with density so great that a teaspoon of Neutron Star: ______________________________ material weighs several thousand tons. _________________________________________ Body of infinite density and gravity so great that Black Hole: _____________________________ not even light can escape. _______________________________________ 37 3. Classifying: _____________________________ __________________________________________ __________________________________________ 38 B. Galaxies: _______________________________ Large systems of stars, __________________________________________ gas, and dust. 1. Composition: _________________________ Millions of stars revolving __________________________________________ around the center of the galaxy Light years wide 2. Size: ________________________________ Our Galaxy, a spiral 3. The Milky Way: ______________________ galaxy( 120,000 Light _________________________________________ years wide) 39 These are galaxy clusters and separate galaxies taken by long-range telescope. The area of the sky covered is less than the diameter of the moon. 40 Contain millions of C. Clusters: ____________________________ __________________________________________ galaxies II. Distance in the Universe A. The speed of light: ___________________ 186,000 miles/sec. _________________________________________ long it takes light to B. The Light Year:How _____________________ _________________________________________ travel in one year 41 III. The Expanding Universe A. The Big Bang Theory: ________________ _________________________________________ _________________________________________ B. Doppler Shift Shows a change in a star's spectrum; evidence that the universe is expanding 1. red shift: ___objects are moving away from us_______________________ __________________________________________ 2. blue shift: __objects are moving towards us_______________________ __________________________________________ Since the spectrum for all galaxies show a _______ from Earth, we assume the universe is __________ 42