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The Earth in Space I. The Solar System - the solar system is described as the Sun, the eight planets (3 dwarfs) that orbit the Sun, and the small interplanetary bodies such as asteroids and comets. A. The Sun - is a medium age star (between 5 and 6 billion years old), and is composed of mainly helium and hydrogen. The sun emits radiation in many wavelengths with temperatures ranging from 7,000 to 90,000 degrees F. The Sun has a period of high activity of solar storms, also called sunspots, every eleven years. B. Terrestrial Planets - these are the four closest planets to the sun that include Mercury, Venus, Earth and Mars. They are mainly composed of rock surrounded by a thin envelope of gas. C. Gas Giants - these are the five outer planets that are mainly composed of water vapor, methane, ammonia gases. They include Jupiter, Saturn, Uranus, Neptune and the 3 dwarfs. D. Asteroids - Located in a belt between Mars and Jupiter, asteroids are rocky objects that range in size from 600 miles across to mere pebbles. There are thousands of asteroids in the solar system. E. Comets - are icy objects that originate from far out of the solar system. Because they are composed of ice, the energy from the Sun vaporizes the ice and forms a comet’s tail. F. Meteorites – smaller chunks of rocks traveling within the solar system. Classified as stony or iron. II. Models of Celestial Motion - A. Geocentric Model of the Universe - this proposed that the earth was the center of the universe, around which all of the stars and planets rotated. This was first proposed by Aristotle, a Greek philosopher (384-322 BC). This did not fully explain the motions of the planets. B. Heliocentric Model of the Universe - this proposed that the earth, along with the other planets orbited around the Sun. This was developed by Nicholas Copernicus , a Polish Astronomer, in 1514. II. Apparent Motion of the Celestial Objects A. Apparent Motion of Celestial Objects - All celestial objects appear to move across the sky in an arc from east to west. The speed of movement of celestial objects is approximately 15 degrees per hour, which is also known as the daily motion. 1. Evidence of the Earth’s Rotation - two pieces of evidence can be used to suggest that the earth is rotating. a. Foucault’s Pendulum - when a pendulum is allowed to swing freely, over time it will change the path of its swing as the earth rotates under it. b. The Coriolis Effect - the tendency of particles on earth to be directed to the right of travel in the Northern Hemisphere. V. The Earth’s Revolution - the earth is also revolving around the Sun. Revolution is the movement of one body around another. The period of the earth’s revolution is 365.25 days. A. --Time and Earth Motions - time is greatly influenced by the motions of the earth, and other celestial bodies. 1. Year - is the time it takes for the earth to make one complete orbit around the Sun. 2. Month - is the time it takes for the Moon to go through one full period of phases. 3. Solar Noon - Time of day when the sun is at its highest altitude above the horizon. The Pale Blue Dot B. Orbital Motion - In our solar system, the earth, moon, and other planet’s orbits are elliptical. An ellipse is a curved path of a moving object. The eccentricity of an ellipse can be determined by the following formula (see reference tables): Eccentricity = distance between foci/length of major axis 1. Earth’s Orbit – 2. Motions of the Moon - The moon revolves around the earth once every 27 1/3 days. Theory of the Moon's Formation - The moon is believed to have been formed when a massive object collided with the Earth early in its formation. a. Phases of the Moon - because the Moon is revolving around the earth, one side is always bathed in shadow from the Sun. When this shadow is observed from earth, it appears to change the visible portion of the Moon. i. The phases of the Moon include: New Moon, New Crescent, First Quarter, New Gibbous, Full, Old Gibbous, Third Quarter, Old Crescent, and New Moon again. iii. The Moon and the Tides - Tides are the result of the gravitational attraction between the Sun, Moon, and Earth. The tidal bulge is the high water mark that is raised by the Moon and Sun's Gravity. Neap Tide - Lowest tidal range of the month Spring Tide - Highest Tidal Range of the month - The Moon's tidal force may also flex the earth's outer crust, which may trigger earthquakes and volcanoes. iv. Eclipses - Solar Eclipse - when the moon passes in front of the Sun. - - Lunar Eclipse - when the Earth casts its shadow on the Moon. III. Beyond the Solar System - the solar system is one of 100 billion other stars that together make up the Milky Way galaxy. A galaxy is a huge cluster of stars that spirals around a central point. The solar system is about half way out in the center of one of the arms of the Milky Way. The Milky Way Galaxy is approximately 100,000 light years across. A light year is the distance that light travels in one year (6.25 trillion miles). Light travels at 186, 000 miles per second. The Milky Way is part of a cluster of 30 galaxies in our local area. A. Types of Galaxies - There are three main types of galaxies, spiral, elliptical, and irregular. B. Stars - A star is defined as a large, hot, glowing ball of gas that is powered by nuclear fusion. Stars are classified by their size, temperature, color, and brightness. This classification is usually based on a stars age or stage of life. The various stages and types of stars include: nebula, proto-stars, main sequence, dwarfs, giants, super giants, neutron stars, pulsars, super nova, and black holes. Interstellar medium Nebula Protostar Main Sequence Red Giant Planetary Nebula White Dwarf Red Supergiant Super Nova Black Hole Neutron Star – Pulsar Star System Formation 1. Star Classification - The Hertzsprung- Russell or HR diagram is used to classify stars by their color, temperature, and luminosity. 2. Spectral Analysis and Doppler Shift - Spectrum - (continuous spectrum) The different wavelengths of visible light (VIBGYOR). - Full Spectrum - A complete spectrum with no breaks. - Bright Line Spectrum-(Emission Spectrum) Specific wavelengths of visible light emitted from a substance. - Dark Line Spectrum - (Absorption Spectrum) Specific Wavelengths of visible light a - Spectral Classification of Stars - Stars are classified by their unique spectral lines. Stars have unique spectral fines mainly due to their different temperatures. Spectral Class Effective Temperature (K) M/MSun R/RSun O 28,000 - 50,000 20 - 60 9 - 15 B 10,000 - 28,000 3 - 18 3.0 8.4 A 7,500 - 10,000 2.0 - 3.0 1.7 2.7 F 6,000 - 7,500 1.1 - 1.6 1.2 1.6 G 4,900 - 6,000 0.85 1.1 0.85 1.1 Spectral Class Effective Temperature (K) M/MSun R/RSun K 3,500 - 4,900 0.65 0.85 0.65 0.85 M 2,000 - 3,500 0.08 0.05 0.17 0.63 L? <2,000 - Doppler Shift - The change in wavelength associated with a moving object. If the object is moving towards you the waves are compressed and the wavelength is decreased due to the objects forward motion (blue shift). If the object is moving away from you, the waves are separated and the wavelength is increased due to the object moving away from you (red shift). - - Galactic Motion - observations of other galaxies based on Doppler shift suggest that all objects in the universe are traveling away from one central point. This has given rise to the Big Bang theory, which describes that all matter and energy were at one central point about 13 -15 billion exploded outward forming the universe as we know it. years ago, and Intelligent Life in the Universe The Drake Equation – N = R* x fp x ne x fl x fi x fc x L N = Number of Intelligent Civilizations in the Milky Way Galaxy R* = How many stars form per year in the galaxy fp = What percent of theses stars have planets ne = of these plants what percent would harbor life fl = of these planets what percent would life be able to evolve fi = of these planets what percent would intelligent life be able to evolve fc = of these planets what percent would develop technology L = How long would a technological society last?