Astronomy 1040 – Flashcards
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Declination
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The angular distance in degrees of an object north or south of the celestial equator.
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Right Ascension (R.A)
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The position of an object that is comparable to longitude on Earth; measured in units of hours and minutes.
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Zenith
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The highest point in the sky at any particular time and location.
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Look Back Time
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The fact that we see objects as they were in the past when we look out into space.
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Milky Way Galaxy
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Our star, the Sun, is one of 100 billion stars that form the...
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Constellations
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Patterns we create in the sky to symbolize important stories and to locate things in the sky.
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Degree
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A unit of angular measure equal to 1/360th of a full circle.
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Astronomical Unit (AU)
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The average distance between Earth and Sun
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Big Bang
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All evidence indicates that the universe started 13.75 billion years ago in the...
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Planet
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A large object that directly orbits a star and is massive enough to both become a sphere and to mostly clear out the debris in its orbit.
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Supercluster
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An enormous clumping of thousands of galaxies.
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Local Group
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Our galaxy is a part of the _____ of about 24 galaxies.
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Solar System
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All the stuff going around our Sun including our own planet and the Sun.
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Universe
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The sum total of all space, time, matter, energy, puppy dogs, etc.
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Observable Universe
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All the stuff that we can see that is closer than 13.75 billion ly away.
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Azimuth
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The position along the horizon that one should face to see a particular object in the sky.
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Altitude
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The angular distance above the horizon of a particular object in the sky.
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Comet
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A small object made mostly of ice and a little rock that is orbiting a star.
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Asteroid
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A small object made mostly of rock, and maybe some ice, that is orbiting a star.
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Rotation
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Most objects in the universe spin. This is called...
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Arcminute
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One sixtieth of a degree. (1/60)
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Arcsecond
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One sixtieth of an arcminute or 1/3600 of a degree.
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Axis Tilt
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Earth's axis is 23.5 degrees off from being perpendicular to our orbit. We call this...
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Summer Solstice
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That time when Earth's northern pole is tipped the most toward the Sun.
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Solstice
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This literally translates as "Sun stop" because the north-south motion of the Sun stops and goes in the other direction at this time.
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Vernal Equinox
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The Northern Hemisphere time when the Sun crosses the celestial equator heading northward.
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Ecliptic
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The apparent path of the Sun against the background stars over the course of a year.
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Zodiac
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The constellations that fall along the ecliptic. It translates from Greek as "circle of animals."
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Phases of the Moon
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The shape of the illuminated portion of the Moon that we see changes, this is the...
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Synchronous Rotation
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The same side of the Moon always faces Earth (ignoring a tiny wobble) this is called...
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Lunar Eclipse
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When Earth's shadow falls on the Moon we call it a... (Might be total or partial.)
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Solar Eclipse (not total)
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This happens when the Sun-Moon-Earth are in a direct line (in that order.) The solar eclipse is only total in one spot and is partial or no eclipse else on that side of Earth.
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Umbra
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The darkest part of an object's shadow, i.e., where the entire light source is blocked.
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Penumbra
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That part of an object's shadow where only part of the Sun is blocked from view.
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Retrograde Motion
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Ancient civilizations had troubles explaining the odd motion of the planets, especially...
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Geocentric
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It is difficult to explain the motions of the heavens for a universe that is believed to be..
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Stellar Parallax
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The main problem with accepting that Earth orbited the Sun was the inability to detect any shifting in the stars as we orbit the Sun. This apparent shifting of the stars is called...
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Heliocentric
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Our modern understanding has us at a random spot in our galaxy in a solar system that is...
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Total Lunar Eclipse
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This happens when the moon is completely inside the darkest part of Earth's shadow.
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Hypothesis
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An educated guess on the part of a scientist as she prepares to study some phenomena.
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Aristotle
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The Greek philosopher who defined our view of the natural world for nearly 2k years.
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Galileo
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The "Father of Modern Science" who defined what we now know as "the scientific method."
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Kepler
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He figured out the motion of the planet including that they travel on elliptical paths. He abandoned the idea of perfect circles and solved the riddle of planetary orbits.
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Period
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The time required for an object to complete one orbit around the Sun is the...
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Occam's Razor
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The philosophy that simple theories are usually better than complicated ones.
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Astrology
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An ancient religion now known to be completely unfounded on anything factual.
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Parallax
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Small "shifting" of relatively nearby objects compared to distant ones when viewed from different places.
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Newton
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He provided the understanding of the "cause" of planetary motion.
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Newton's Laws of Motion
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Three laws that describe the motion of pretty much any object on Earth or in space.
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Kepler's Laws
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Three laws that describe the motion of planets around a star.
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Theory
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Typically, only well accepted ideas with vast amounts of testing and data become...
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Semimajor Axis
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This is used for ellipses like "radius" is used for circles.
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Paradigm
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A generally accepted pattern of thought and/or model is known as a...
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Light Gatherin Ability
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This is a measure of how much light a telescope can collect. It is more important than mgnification for most aastronomical uses.
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Reflecting telescope
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Almost all research telescopes use a mirror to gather light, this type of telescope is a...
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Universal Law of Gravitation
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This idea explained a lot about falling objects, orbiting planets, returning comets, etc.
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Ptolemy
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The Greek philosopher who defined a complicated model of the geocentric universe.
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Copernicus
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He wrote 'De Reolutionibus Orbium Coelestium,' which describes a heliocentric solar system. Unfortunately, it was only slightly better than that by C. Ptolemy.
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Sun
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The larest object in the solar system. It dominates all aspects of the solar system.
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Terrestrial Planets
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The class of planets that includes Earth, Mercury, Venus and Mars.
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Jovian Planets
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The class of planets that includes Jupiter, Saturn, Uranus and Neptune.
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Asteroid
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A small orbiting object that is comprised of metal and rock.
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Asteroid Belt
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The collection of debris that is located between the orbits of Mars and Jupiter.
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Kuiper Belt
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A donut shaped ring of icy bodies past Neptune that contains many dwarf planets.
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Oort Cloud
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A vast and very distant halo of small icy bodies that surrounds our solar system.
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Conservation of Energy
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Energy can be converted between forms but cannot be created or destroyed.
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Conservation of Angular Momentum
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If there are no external forces, spinning objects must obey the law of...
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Solar Nebula
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Our star and the solar system very likely formed from a large gas cloud called the...
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Nebular Theory
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The idea that stars and their planets formed from the collapse of large gas clouds. As we learn more from newly discovered extrasolar systems, we may need to modify it.
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Condensation
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At very low temperatures some atoms and molecules will start to stick together.
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Accretion
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The process by which larger particles start to stick together, mostly by gravity.
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Frost Line
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As the solar system formed, icy stuff and gases collected further from the Sun, meanwhile rocky and metallic particles accreted closer to the Sun. The dividing line is the...
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Heavy Bombardment
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Early in the history of our solar system there were lots of small objects pounding into all the planets and moons, leaving a lot of craters.
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Giant Impact
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Earth's Moon was likely caused by a XXXXX between Earth and a huge plantesimal.
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Radiometric Dating
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Measurements of the abundance of different radioactive isotopes to determine age.
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Half-Life
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If you start with a kilogram of radioactive material after one _______ you will only have 500 grams left. After yet another _______ you will only have 250 grams left.
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Helium
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When our Solar System formed the vast majority of the material was hydrogen and...
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Dwarf Planet
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Sadly for kids everywhere, scientists have demoted Pluto to being only a...
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Differentiation
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Higher density material sinks to a planet's center and less dense materials float to the top.
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Core
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The center of a planet's structure where the highest density materials reside.
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Mantle
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A region inside of a planet that contains medium density rocks bearing silicon and oxygen.
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Lithosphere
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A rigid region of rock that "floats" on the softer molten (or core) rock below.
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Crust
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A very thin layer of rock that is the outer most layer of all terrestrial planets.
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Impact Cratering
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When asteroids or other objects strike a planet or moon the surface is changed through...
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Volcanism
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Molten rock from a planet's inner layers coming to the surface.
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Plate Tectonics
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When a planete's lithosphere cracks and moves about causing surface changes.
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Erosion
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The reshaping of a planet's surface by wind, water and ice.
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Electomagnetic Spectrum
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Photons of any wavelength from infared through gamma rays.
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Ozone (O3)
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Located in the middle of the stratosphere this layer of our atmosphere protects us from ultraviolet radiation.
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Thermal Radiation
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The temperature of an object can be measured by observing the most intense wavelength.
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Greenhouse Effect
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Different wavelengths of light can pass through an atmosphere or are blocked. This causes a planet to warm up.
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Global Warming
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The addition of anthropogenic CO2 and other gases is causing climate change on Earth.
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Lunar Maria
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Parts of the Moon's surface have been flooded with lava forming smooth "seas."
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A Magnetic Field
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Spinning Planets with fluid electrically conductive cores form...
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Convection
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The movement of fluids (liquids and gases) caused by uneven heating.
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Outgassing
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The release of gases mostly CO2 especially from a planet's volcanoes.
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CO2 Cycle
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Our planet regulates its temperature over time by this process.
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Metallic Hydrogen
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The magnetic fields of Jupiter and Saturn are generated by the electrically conductive..
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Rings
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All four gas giants have ______ of countless icy particles surrounding them.
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Moonlets
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Planetary rings are not ephemeral but are constantly being renewed, the source seems to be...
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Tidal Heating
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Some moons are geologically active with ice and sulfur volcanoes, this energy comes from...
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Tidal Force
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The force of gravity drops with distance, thus the near and far side of a planet or moon have different amounts of gravitational attraction to each other.
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Galilean Moons
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Jupiter has 4 large moons that can easily be seen in binoculars.
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Io
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This amazing moon is the most geologically active body in the solar system.
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Europa
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This moon of Jupiter probably has a liquid ocean under its ice covered surface.
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Ganymede
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Io, Europa and XXXXX have orbital resonances that help to generate tidal heating.
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Callisto
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This outermost large moon of Jupiter seems to be just a dead ice ball.
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Mass Extinction
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Earth gets hit every few million years by a large comet or asteroid sometimes causing as...
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Impact Threat
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We monitor thousands of near Earth orbiting asteroids because some of them may be an...
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Voyager 2
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Just this one spacecraft has journeyed past all 4 Jovian Planets giving us our only close views of Uranus and Neptune.
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Titan
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This largest moon of Saturn is the only moon in the solar system with a thick atmospher.
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Great Red Spot
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Jupiter's large hurricane-like storm that is visible in small telescopes from Earth.
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Bars (Pressure)
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This is a unit of measure of atmospheric pressure, at Earth's surface the value is about 1.
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Extrasolar Planets
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Planets orbiting other stars instead of our Sun.
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Direct Detection
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Visually seeing, photographing or taking spectral data of extrasolar planets. It is very difficult to find planets this way because they are so close to the star and the star is about a billion times brighter than the planet.
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Indirect Detection
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Measuring the motion of a star and then deducing the presence of planets.
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Astrometric Technique
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Measuring planet caused wobble directly by plotting the path of a star.
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Doppler Technique
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Measuring planet caused wobble by observing the shift in wavelength caused by motion.
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Doppler Effect
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Motion along the line of sight that causes a shift in an object's spectra.
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Blueshift
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The Doppler shift when you and an object are moving toward each other.
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Redshift
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The Doppler shift when you and an object are moving away from each other. We see this in looking at the spectral lines of any objects moving away from us.
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Hot Jupiter
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Jupiter-like mass planets that orbit close to their star and have high surface temperatures.
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Transit
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By observing the brightness of a star you can deduce if a planet passes in front of the star. When a planet passes in front of a star it is called a XXXXX.
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'Kepler'
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This spacecraft was launched in 2009 and has already found several Earth sized planets.
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Center of Mass
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Planets don't orbit the star's center; the two objects orbit about their common XXXXX.
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Planetary Migration
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It is possible that planets can form in one orbit then move to a new orbit.
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Luminosity
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The total energy generated by a star, expressed in watts or by comparison to our Sun.
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Fusion
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The source of energy used by our Sun or a star. Our largest weapons do this too.
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Fission
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The source of energy used by current nuclear power plants and for simple nuclear bombs.
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Strong Force
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This force keeps the nucleus of an atom together by overcoming the electromagnetic force.
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Spectroscopy
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We learn about stars by studying their light.
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Emission LIne
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This is the type of spectra we get from hot gases.
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Absorption Line
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Cool gases have dark lines against a smooth broad background of colors.
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Photosphere
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The mottled appearing part of the Sun that we consider as the "surface."
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Chromosphere
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The lower part of the solar atmosphere.
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Corona
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The large, hot, outer portion of the solar atmosphere that artists often draw as a halo.
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Sunspot
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Earth-sized storms on the Sun from loops of magnetic fields poking out of the surface.
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Sunspot Cycle
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An approximately 11 year interval of storm activity on the Sun.
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Solar Wind
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A stream of charged atomic and subatomic particles continually leaving the Sun.
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Inverse Square Law
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The apparent brightness of a star drops off by the square of its distance away.
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Spectral Type
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Our Sun is a G2 star. This is our star's XXXXX.
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Main Sequence
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The line of stars that snakes across the H-R diagram from upper left toward lower right.
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Giant
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Stars toward the top right of an H-R diagram.
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White Dwarf
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Stars at the lower left corner of an H-R diagram. The very hot dead corpse of our Sun. This will slowly cool down in time and fade away.
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Magnitude System
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An older, but still standard, method for measuring stellar brightness.
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Molecular Clouds
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Giant, cold, dark clouds - made mostly of hydrogen molecules - where stars are born.
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Gravitational Equilibrium
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For a star to be stable it must balance the forces of gravity and gas pressure.
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Electron Degeneracy Pressure
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The internal pressure in stars and gas giants arising from atoms having no place else to go. The laws of quantum mechanics don't allow electrons to share the same space.
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Stellar Thermostat
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Gravitation equilibrium and energy balance must be maintained.
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Hydrogen Shell Burning
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When our Sun runs out of hydrogen in its core the surrounding layers collapse and start this.
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Planetary Nebula
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When our Sun dies it will blow its outer layers off into space and become a large...
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Supernova
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The iron core of a massive star cannot produce energy. It collapses and explodes as a...
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Main Sequence Turnoff Point
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We use this to determine the age of a cluster of stars.
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Chandrasekhar Limit
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A white dwarf's mass must be <1.4Msun or else it will collapse.
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Nova
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The explosion that comes from hydrogen gas accreting onto the surface of a white dwarf.
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Neutron Star
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In these stars gravitational pressure exceeds the limit of electron degeneracy pressure.
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Neutron Degeneracy Pressure
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Neutron stars are bizarrely massive; only this keeps it from collapsing more.
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Pulsar
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A rapidly spinning neutron star. At first we thought this might be alien communications.
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Black Hole
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When Neutron degeneracy pressure can no longer support the star it collapses into a...
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Escape Velocity
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A measure of the amount of energy needed to escape from the gravity of an object.
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General Relativity
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Einstein's theory, published in 1915, which explains gravity and the curvature of space.
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Event Horizon
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This is the point of no return for an object entering too close to a black hole.
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Schwarzschild Radius
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The size of a black hole, this is determined by the amount of mass.
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Singularity
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The center of a black hole >3Msun, is an infinitely dense, infinitesimally small particle.
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Supermassive Blackhole
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Many spiral galaxies contain one of these massive objects at their centers. These are the likely energy source for quasars.
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Evolutionary Track
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The plot of a star's life on an H-R diagram.
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Mass
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The one property of a star that will tell us almost everything we need to know about the star.
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Spiral Arms
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These large structures give galaxies like ours their characteristic pinwheel shape.
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Disk
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This is what spiral galaxies look like when viewed edge on.
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Central Bulge
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At the center of the disk of spiral galaxies is the large, bright...
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Halo
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This is a vast region of mostly globular clusters that surround the disk of our galaxy.
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Globular Cluster
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There are spherical clumps of old stars, typically containing a few hundred thousand to a million stars.
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Interstellar Medium
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Most of the galactic disk is comprised of stars and this dust and gas between the stars.
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Star-Gas-Star Cycle
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Most active star formation happens in our galaxy's disk. These stars are undergoing the...
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21 Centimeter Line
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Hydrogen gas is mapped in our galaxy using radio telescopes looking at this spectral line.
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Ionization Nebulae
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These nebulae glow brightly because of the energy being emitted by hot, young, stars.
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Sprial Density Waves
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These disturbances shape the spiral arms of our galaxy and trigger new star formation.
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Disk Population Stars
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These are stars, like our Sun, that contain about 2% heavy elements.
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Spheroidal Population Stars
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These are old stars that contain very few heavy elements.
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Protogalactic Cloud
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Similar to our solar system, but on a much larger scale, our galaxy started out as a...
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Spiral Galaxy
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This class of galaxy includes our Milky Way. They all have spiral arms.
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Elliptical Galaxy
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These galaxies are shaped like a giant football. Stars orbit randomly in these galaxies.
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Irregular Galaxy
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These are oddly shaped galaxies with no clear pattern from one to the next.
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Active Galactic Nuclei
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The centers of some galaxies are extremely bright and emit a spectrum that is different from the spectrum emitted by typical stars in that galaxy's disk.
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Quasar
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The most luminous objects known. They out shine 1k galaxies like ours yet only take up a small amount of space, no larger than our solar system.
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Radar Ranging
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We use this method for finding the distances to nearby objects like asteroids and Mercury.
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Parallax
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This method of distance measurment is used for nearby stars up to about 10k ly away.
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Standard Candle
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If we know how luminous an object is, we can use it to measure distance as a...
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Main-Sequence Fitting
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For star clusters we can use the H-R diagram to determine distance, this ...
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Cepheid Variable Stars
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These special stars vary in brightness and are used for measuring distances to galaxies.
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Period-Luminosity Relation
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We measure the light curve then use this to determine the luminosity of Cepheids.
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Distant Standard
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White Dwarf supernovae can tell us the distance to far away galaxies.
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Hubble's Law
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The more distant a galaxy is from us, the faster it is moving away.
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Hubble's Constant
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Our knowledge of the expansion of the universe depends on a good measurement of this value.
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Cosmological Redshift
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Motion through space results in Doppler redshift, motion due to the expansion of space is called...
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Expanding Universe
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This surprising behavior of our Universe was discovered by Edwin Hubble.
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Cosmological Principle
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As far as we can tell, there is no center or edge to our Universe, we call this the...
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Cosmological Horizon
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We cannot see further away than 14b ly.
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Antimatter
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An electron is a particle of matter, whereas a positron is a particle of XXXXX.
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Planck Era
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Current theories don't work this early in the Universe's history, when all forces were one.
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GUT Era
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The Universe cools a bit; gravity condenses out from the Grand Unified Force at this time.
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Electroweak Era
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The Universe cools some more and the strong force is condensed out during this time.
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Particle Era
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During this time photons were spontaneously producing protons and antiprotons.
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Era of Nucleosynthesis
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After most anitmatter was destroyed, some remaining protons formed nuclei at this time.
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Era of Nuclei
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During this era the cooling Universe's atoms were still too hot to stay together.
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Era of Atoms
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Electrons stayed with protons, atoms became stable, and photons moved easily at this time.
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Era of Galaxies
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At about 1b years old the Universe cooled enough that large structures formed.
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CMB
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At the start of the era of atoms photons could move freely. We see this today as the...
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Inflation
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At 10^-38 seconds, this event probably occurred, eventually leading to galaxy formation.
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Dark Matter
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We cannot see the majority of the Universe, but we measure its gravity.
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Rotation Curve
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A plot of measurement of orbital velocity vs. distance from an object.
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Gravitational Lens
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Gravity from a galaxy cluster can bend light around itself, distorting objects behind it.
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MACHOs
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Dark matter might be big objects like faint stars and brown dwarfs.
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WIMPs
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Dark matter might be subatomic particles that don't interact strongly with anything.
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Large-Scale Structures
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On huge scales the Universe is not random but has vast walls and voids of galaxies.
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Dark Energy
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Recent discoveries indicate that this is overpowering gravity and speeding up expansion.
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Big Crunch
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With no dark energy and enough gravitational mass, the re collapsing universe will end as...
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Closed Universe
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A re collapsing universe is also known as a...
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Coasting Universe
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Without dark energy and with too little mass to re collapse, our universe will be a...
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Accelerating Universe
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Our best current evidence indicates that there is a repulsive dark energy making us an...
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DNA
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The molecule that makes up the genetic material for all know forms of life.
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Tree of Life
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A graphic that depicts the relationships among all living species.
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Extremophiles
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Microbes that live in very hostile environments. Proof that life can live in a much wider range of conditions then we used to think was possible.
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Habitable World
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A world on which at least some type of Earth-like life could exist.
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Habitable Zone
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The region around a star where an orbiting planet has the chance to maintain liquid water.
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SETI
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The overall attempt to determine if there are other forms of intelligent life in the universe.
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Drake Question
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A method to estimate the number of other possible civilizations in our galaxy.
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UFO
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Any moving object in the sky that you don't recognize as something you're familiar with.
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Fermi's Paradox
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If there are so many civilizations in the galaxy, why haven't we heard from them? So where is everybody?
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Evolution
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As solid as the theory of gravity, this theory explains the changes in time of living things.
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Natural Selection
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The process by which evolution proceeds.
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Miller-Urey Experiment
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Proof that lightning and primordial elements can create the basic building blocks of life.
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Extraterrestrial Life
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Life beyond Earth
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Pioneer Plaque
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A message from Earth attached to a spacecraft that shows a man an woman and our origins along with info on how to decode the information.
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Voyager Record
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A message from Earth attached to a spacecraft that contains sounds from Earth such as greetings in many languages, music, nature sounds, etc.
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Alien Abductions
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The claimed removal (in body or spirit) and return of people from Earth for experiments.
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Alien Autopsy
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A ridiculous TV program that claims to be a documentary of alien studies.
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Alien Visitation
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Claims that aliens from other worlds have been among us.
