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EARTH SCIENCE VOCABULARY: THE UNIVERSE Please see pages 658-694 of your textbook. ILLUSTRATION OWN WORDS DEFINITION OFFICIAL MEANING Astronomy is a natural science that deals with the study of celestial objects (such as moons, planets, stars, nebulae, and galaxies); the physics, chemistry, and evolution of such objects; and phenomena that originate outside the atmosphere of Earth (such as supernovae, gamma ray bursts, and cosmic background radiation). TERM 1. Astronomy A galaxy is a massive, gravitationally bound system consisting of stars, stellar remnants, an interstellar medium of gas and dust, and an important but poorly understood component called dark matter. The word galaxy is derived from the Greek galaxias γαλαξίας, literally "milky", a reference to the Milky Way. 2. Galaxy The electromagnetic spectrum is the range of all possible frequencies of electromagnetic radiation. The electromagnetic spectrum extends from below the low frequencies used for modern radio communication through visible light and on to gamma radiation at the shortwavelength (high-frequency) end, thereby covering wavelengths from thousands of kilometers down to a fraction of the size of an atom. An instrument designed to detect visible light, radio waves, x-rays or another part of the electromagnetic spectrum emanating from a source that is distant. Translated, “telescope” means “see at a distance.” They may be used to make observations on earth (for example, a ship at see looking at a coastline) or to observe other objects in the universe. 3. Electromagnetic Spectrum 4. Telescope A telescope in which electromagnetic radiation from the object is gathered and focused by a concave mirror, with the resulting image magnified by the eyepiece or camera. Many reflecting telescopes are designed for use by amateur astronomers, and can easily be carried around. 5. Reflecting Telescope ILLUSTRATION OWN WORDS DEFINITION OFFICIAL MEANING A telescope in which light from an object is gathered and focused by lenses, with the resulting image magnified by the eyepiece. Refracting telescopes do not use mirrors to focus the image. TERM 1. Refracting Telescope A rotation is a circular movement of an object. A three-dimensional object rotates always around an imaginary line called a rotation axis. If the axis is within the body, and passes through its center of mass the body is said to rotate upon itself, or spin. Each time the Earth completes another day, it has completed a rotation. 2. Rotation A revolution is a circular movement of an object around another object or point in space. Each time the Earth completes another year, it has completed a revolution. 3. Revolution The perihelion is the point in the orbit of a planet, asteroid or comet where it is nearest to the sun. The word perihelion stems from the Greek words "peri" (meaning "near") and "helios" (meaning "sun"). All planets, comets and asteroids in our solar system have elliptical (non-circular) orbits. Thus, they all have a closest and a farthest point from the sun: a perihelion and an aphelion. 4. Perihelion The aphelion is the point in the orbit of a planet, asteroid or comet where it is nearest to the sun. The word perihelion stems from the Greek words "apo” meaning “away, off, apart” and "helios" (meaning "sun"). All planets, comets and asteroids in our solar system have elliptical (non-circular) orbits. Thus, they all have a closest and a farthest point from the sun: a perihelion and an aphelion. 5. Aphelion The date on which the day and night of the Earth (or another planet) are most equal. It is from the Greek words meaning “equal night.” On Earth, there are two equinoxes, one in Spring (approximately March 20) and one in Autumn (approximately September 22), when the day and night are both 12 hours long. 6. Equinox The day of the solstice is either the "longest day of the year" or the "shortest day of the year" for any place on Earth, because the length of time between sunrise and sunset on that day is the yearly maximum or minimum for that place. The name is derived from the Latin words sol (“sun”) and sistere (“to stand still”). During the solstice, the Sun stands still; that is, the seasonal movement of the Sun's path comes to a stop before reversing direction The collection of planets and their moons in orbit around a sun, together with smaller bodies such as asteroids, meteoroids, and comets. 7. Solstice 8. Solar System Greek astronomers employed the term asteres planetai (άστέρες πλανηται), "wandering stars", for objects which apparently move over the sky. A planet is a body that orbits the Sun, is massive enough for its own gravity to make it round, and has "cleared its neighborhood" of smaller objects around its orbit. Under this new definition, Pluto and the other transNeptunian objects do not qualify as planets. Gaseous cloud from which, in the nebular hypothesis of the origin of the solar system, the Sun and planets formed by condensation. In 1755 Immanuel Kant suggested that a nebula gradually pulled together by its own gravity developed into the Sun and planets. A modified version, in which a rotating disk of matter gave rise to the planets through successively larger agglomerations, from dust grains through planetesimals and protoplanetsis the currently best-believed theory of the solar system's origin. 9. Planet 10. Solar Nebula EARTH SCIENCE VOCABULARY: THE UNIVERSE PART 2 Please see pages 658-694 of your textbook. ILLUSTRATION OWN WORDS DEFINITION OFFICIAL MEANING The word planetesimal comes from the mathematical concept infinitesimal and literally means an ultimately small fraction of a planet. A planetesimal is a solid object arising during the accumulation of planets whose internal strength is dominated by self-gravity and whose orbital dynamics is not significantly affected by gas drag. This corresponds to objects larger than approximately 1 km in the solar nebula. A measure of the deviation of an elliptical path, especially an orbit, from a perfect circle. It is equal to the ratio of the distance between the foci of the ellipse to the length of the major axis of the ellipse (the distance between the two points farthest apart on the ellipse). Eccentricity ranges from zero (for a perfect circle) to values approaching 1 (highly elongated ellipses). TERM 11. Planetisimal 12. Eccentricity The orbital period is the time taken for a given object to make one complete orbit about another object. The earth takes one year to revolve around the sun; this is its orbital period. 13. Orbital Period Inertia is the resistance of any physical object to a change in its state of motion or rest, or the tendency of an object to resist any change in its motion. The principle of inertia is one of the fundamental principles of classical physics which are used to describe the motion of matter and how it is affected by applied forces. Inertia comes from the Latin word, iners, meaning idle, or lazy. 14. Inertia The parsec (symbol: pc) is a unit of length used in astronomy. It is about 3.26 lightyears, which is about 30.9 trillion (3.09×1013) kilometers or about 19.2 trillion (1.92×1013) miles. 15. Parsec ILLUSTRATION OWN WORDS DEFINITION OFFICIAL MEANING A light-year, also light year or lightyear (symbol: ly), is a unit of length equal to just under 10 trillion kilometers (or about 6 trillion miles). As defined by the International Astronomical Union (IAU), a light-year is the distance that light travels in a vacuum in one Julian year TERM 16. Lightyear An astronomical unit (abbreviated as AU) is a unit of length equal to exactly 149,597,870,700 meters, approximately the mean Earth–Sun distance. 17. Astronomical Unit (A.U.) A natural satellite or moon is a celestial body that orbits a planet or smaller body, which is called its primary. Formally classified moons include 176 planetary satellites orbiting six of the eight planets, and eight orbiting three of the five IAU-listed dwarf planets. 18. moon In astronomy, the geocentric model (also known as geocentrism, or the Ptolemaic system), is the theory that the Earth is the orbital center for all celestial bodies.. As such, most Ancient Greek philosophers assumed that the Sun, Moon, stars, and all known planets circled the Earth. This viewpoint continued until 1838, when astronomical observations showed it could not be correct. Retrograde motion is motion in the direction opposite to the movement of something else. This motion can be the orbit of one body about another body or about some other point, or the rotation of a single body about its axis. In reference to celestial systems, retrograde motion usually means motion which is contrary to the rotation of the primary, that is, the object which forms the system's hub. All eight planets in our solar system orbit the Sun in the direction that the Sun is rotating. Six of the planets also rotate about their axis in this same direction. The exceptions—the planets with retrograde rotation—are Venus and Uranus. 19. geocentric 20. retrograde motion ILLUSTRATION OWN WORDS DEFINITION OFFICIAL MEANING In the heliocentric solar system, the planets revolve around a relatively stationary Sun at the center of the Solar System. The word comes from the Greek (ἥλιος helios "sun" and κέντρον kentron "center"). Historically, heliocentrism was opposed to geocentrism, which placed the Earth at the center. Heliocentric models were suggested as early as the 3rd Century BCE, but did not become popular until the 1800s. Gravitation, or gravity, is a natural phenomenon by which physical bodies attract each other with a force proportional to their masses. Gravitation is most familiar as the agent that gives weight to objects with mass and causes them to fall to the ground when dropped. Gravity is responsible for the formation of solar systems and their parts, and for keeping the parts in orbit. The four inner or terrestrial planets have dense, rocky compositions, few or no moons, and no ring systems. They are composed largely of silicates, and metals such as iron and nickel. Three of the four inner planets (Venus, Earth and Mars) have atmospheres substantial enough to generate weather; all have impact craters and tectonic surface features such as rift valleys and volcanoes. A terrestrial planet, telluric planet or rocky planet is a planet that is composed primarily of silicate rocks or metals. Within the Solar System, the terrestrial planets are the inner planets closest to the Sun. The terms are derived from Latin words for Earth (Terra and Tellus), as these planets are, in terms of composition, "Earth-like". Terrestrial planets have a solid planetary surface In the broadest sense, the term impact crater can be applied to any depression, natural or manmade, resulting from the high velocity impact of a projectile with a larger body. In most common usage, the term is used for the approximately circular depression in the surface of a planet, moon or other solid body in the Solar System, formed by the hypervelocity impact of a smaller body with the surface. In contrast to volcanic craters, which result from explosion or internal collapse,[1] impact craters typically have raised rims and floors that are lower in elevation than the surrounding terrain. TERM 21. heliocentric 22. Gravity 23. Inner Planets 24. Terrestrial Planets 25. Impact Crater ILLUSTRATION OWN WORDS DEFINITION OFFICIAL MEANING The greenhouse effect is a process by which thermal radiation from a planetary surface is absorbed by atmospheric greenhouse gases, and is re-radiated in all directions. Since part of this re-radiation is back towards the surface and the lower atmosphere, it results in an elevation of the average surface temperature above what it would be in the absence of the gases TERM 26. Greenhouse Effect The outer planets are those planets in the Solar System beyond the asteroid belt, and hence refers to the gas giants, which are in order of their distance from the Sun: Jupiter, Saturn, Uranus and Neptune. All four planets have rings, although Saturn’s are far more obvious. Another aspect common to the gas giants is their many natural satellites, two of which are larger than the planet Mercury (Jupiter's Ganymede and Saturn's Titan). That pair and Io, Callisto, Europa, and Triton, are larger than Pluto and Eris. This region of space is also occupied by centaurs, various fields of trojans, and many comets. The asteroid belt is the region of the Solar System located roughly between the orbits of the planets Mars and Jupiter. It is occupied by numerous irregularly shaped bodies called asteroids or minor planets. About half the mass of the belt is contained in the four largest asteroids, Ceres, Vesta, Pallas, and Hygiea.. The remaining bodies range down to the size of a dust particle. 27. Outer Planets A gas giant (sometimes also known as a jovian planet after the planet Jupiter, or giant planet) is a large planet that is not primarily composed of rock or other solid matter .They do not have a solid surface. There are four gas giants in the Solar System: Jupiter, Saturn, Uranus, and Neptune. Many extrasolar gas giants have been identified orbiting other stars. The smallest stars (“Brown Dwarves”) are about 13 times the size of Jupiter. The Galilean moons are the four moons of Jupiter discovered by Galileo Galilei in January 1610. They are the largest of the many moons of Jupiter and derive their names from the lovers of Zeus: Io, Europa, Ganymede, and Callisto. They are among the most massive objects in the Solar System outside the Sun and the eight planets, with radii larger than any of the dwarf planets 29. Gas Giants 28. Asteroid Belt 30. Galilean Moons ILLUSTRATION OWN WORDS DEFINITION OFFICIAL MEANING A very large, high-pressure atmospheric feature on the planet Jupiter, characterized by anticyclonic winds circulating at a speed of approximately 400 km (248 mi) per hour. The storm has persisted on Jupiter's surface for more than 300 years (since first observed through telescopes); the cause of its reddish color is unknown. A secondary effect of the gravitational forces between two objects orbiting each other, such as the Earth and the Moon, that tends to elongate each body along the axis of a line connecting their centers. Tidal forces are responsible for the fluctuation of the oceanic tides as well as for the synchronous rotation of certain moons as they orbit their planets TERM 31. Great Red Spot 32. Tidal Forces