Help
Options
Didn't know it?
click below
click below
Knew it?
click below
click below
Don't Know
Remaining cards (0)
Know
retry
shuffle
restart
0:00
Embed Code - If you would like this activity on your web page, copy the script below and paste it into your web page.
Normal Size Small Size show me how
Normal Size Small Size show me how
Astronomy
Astronomy terms and definitions
| Term | Definition |
|---|---|
| Accelerate | Change in velocity |
| Apparent Magnitude | How bright a star looks in the sky |
| Astrology | Pseudoscience dealing with the effects on humans of the locations and configurations of celestial bodies |
| Celestial Equator | Circle on the celestial sphere ninety degrees from the celestial poles; where the celestial sphere intersects the plane of the Earth's equator |
| Celestial Poles | Points about which the celestial sphere appears to rotate; intersections of the celestial sphere with Earth's polar axis |
| Celestial Sphere | Apparent sphere of the sky, centered on the observer; directions of celestial objects can be denoted by their position on the sphere |
| Circumpolar Zone | Portions of the celestial sphere near the celestial poles that are always above or below the horizon |
| Cosmology | Study of the origin and evolution of the universe |
| Ecliptic | Apparent annual path of the sun on the celestial sphere |
| Geocentric | Centered on the Earth |
| Heliocentric | Centered on the Sun |
| Horizon | Great circle on the celestial sphere ninety degrees from the zenith; the circle around us where the dome of the sky meets the Earth |
| Horoscope | Chart used by astrologers that shows the positions along the zodiac and in the sky of the Sun, Moon, and planets at some given time, usually corresponding to the time of a person's birth |
| Parallax | Apparent displacement of a nearby star's position that results from the motion of Earth around the Sun |
| Planet | Any of the larger objects revolving around the Sun or any similar objects that orbit other stars |
| Precession | Slow movement of Earth's axis of rotation caused by the gravitational pull of the Moon and Sun on the Earth's gravitational zone |
| Retrograde | Describes motion of a rotating body that is opposite of the body it orbits; motion that is in the same direction of rotation is prograde |
| Year | Period of revolution of Earth around the Sun |
| Zenith | Point on the celestial sphere pointed directly above the observer |
| Zodiac | Belt around the sky occupying about thirty degrees of celestial longitude |
| Angular Momentum | Measure of motion of a rotating object in terms of its speed and how widely the object's mass is distributed around its axis |
| Aphelion | Point in an orbit where a satellite is farthest from the Sun |
| Apogee | Point in an orbit where a satellite is farthest from the Earth |
| Asteroid Belt | Region of the solar system between the orbits of Mars and Jupiter in which most asteroids are located. Extends from 2.2 to 3.3 AU from the Sun |
| Astronomical Unit | Unit of length defined as the average distance between the Earth and the Sun |
| Density | Ratio of the mass of an object to its volume |
| Eccentricity | In an ellipse, the ratio of the distance between the foci to the major axis. |
| Ellipse | Closed curve for which the sum of the distances from any point on the curve to two points inside - called the foci - is always the same |
| Escape Velocity | Speed a body must achieve to break away from the gravity of another body |
| Focus | One of two fixed points inside an ellipse from which the sum of the distances to any point in the ellipse is constant |
| Gravity | Mutual attractions of material bodies or particles |
| Kepler's First Law | Each planet moves around the Sun in an ellipse, with the Sun at one focus of the ellipse |
| Kepler's Second Law | Straight line joining a planet and the Sun sweeps out equal areas in space in equal intervals of time |
| Kepler's Third Law | Square of a planet's orbital period is directly proportional to the cube of the semi-major axis of its orbit |
| Major Axis | Maximum diameter of an ellipse |
| Momentum | Measure of the amount of motion of a body; it is the product of mass and velocity |
| Newton's First Law | Every object that is in motion will stay in motion, and every object that is at rest will stay at rest, unless acted upon by an outside force |
| Newton's Second Law | Force equals mass times acceleration |
| Newton's Third Law | Every action has an equal and opposite reaction |
| Orbit | Path of an object that is in revolution |
| Orbital Period | Time it takes an object to travel once around the primary body |
| Orbital Speed | Speed at which an object orbits around the mass of another object |
| Perigee | Point in an orbit where a satellite is closest to Earth |
| Perihelion | Point in an orbit where a satellite is closest to the Sun |
| Perturbation | Small disturbance on the orbit of a body produced by a third body |
| Satellite | Object that revolves around a planet or other body |
| Semimajor Axis | Half of the major axis in an ellipse |
| Velocity | Speed and direction a body is moving |
| Apparent Solar Time | Time as measured by the position of the Sun in the sky |
| Declination | Angular distance north or south of the celestial equator |
| Great Circle | Circle on the surface of a sphere that is the curve of intersection of the sphere with a plane passing through its center |
| International Date Line | Arbitrary line on the surface of Earth near one hundred and eighty degrees longitude across which the date changes by one day |
| Lunar Eclipse | Eclipse of the moon, in which the moon moves into the shadow of Earth; these can occur at times of a full moon |
| Mean Solar Time | Time based on the rotation of the Earth; passes at a constant rate, unlike apparent solar time |
| Meridian | Great circle on the terrestrial or celestial spheres that passes through the poles |
| Phases of the Moon | Different appearance of light and dark on the Moon as seen from Earth during its monthly cycle, from new moon to full moon and back to new moon |
| Right Ascension | Coordinate for measuring the east-west positions of celestial bodies |
| Sidereal Day | Earth's rotation period as defined by the positions of the stars in the sky; time between successive passages of the same star through the meridian |
| Sidereal Month | Period of the Moon's revolution about Earth measured with respect to stars |
| Solar Day | Earth's rotation as defined by the position of the Sun in the sky; time between successive passages of the Sun through the meridian |
| Solar Eclipse | Eclipse of the Sun by the Moon, caused by the passage of the Moon in front of the Sun; can only occur at the time of the new moon |
| Synchronous Rotation | When a body rotates at the same rate that it revolves around another body |
| Syzygy | Straight-line configuration of three or more celestial bodies |
| Tides | Alternate rising and falling of sea level caused by the difference in the strength of the Moon's gravitational pull on different parts of Earth |
| Absorption Spectrum | Series of dark lines superimposed on a continuous spectrum |
| Blackbody | Objects that absorbs all incident electromagnetic radiation |
| Continuous Spectrum | Spectrum of light composed of radiation of a continuous range of wavelengths or colors, rather than only certain discrete wavelengths |
| Dispersion | Separation of different wavelengths of white light through refraction of different amounts |
| Doppler Effect | Apparent change in wavelength or frequency of radiation from a source due to its relative motion away from or toward the observer |
| Electromagnetic Radiation | Radiation consisting of waves propagated through electric and magnetic fields and traveling at the speed of light |
| Electromagnetic Spectrum | Whole array of electromagnetic waves, from radio to gamma rays |
| Emission Spectrum | Series of bright lines superimposed on a continuous spectrum |
| Energy Flux | Amount of energy passing through a unit of area per second |
| Energy Level | Amount of energy possessed by an atom or ion above the energy it possesses in its ground state |
| Excitation | Process of giving an atom or ion an amount of energy greater than it has in its ground state |
| Frequency | Number of waves that cross a given point per unit of time |
| Gamma Rays | Photons of energy with wavelengths no longer than 0.01 nanometers; the most energized form of electromagnetic radiation |
| Ground State | Lowest energy state of an atom |
| Infrared | Electromagnetic radiation with wavelengths longer than visible light |
| Inverse Square Law | Amount of light flowing through a given area in a given time decreases in proportion to the square of the distance from the source of energy or light |
| Ion | Atom that has become electrically charged by the gain or loss of one or more electrons |
| Ionization | Process by which an atom gains or loses electrons |
| Isotope | Any of two or more forms of the same element whose atoms have a different number of neutrons |
| Microwave | Electromagnetic radiation with wavelengths longer than infrared waves but shorter than radio waves |
| Nucleus | Massive part of an atom composed of protons and neutrons |
| Photon | Discrete unit of electromagnetic energy |
| Radial Velocity | Motion towards or away from the observer |
| Radio Waves | All electromagnetic radiation longer than microwaves |
| Spectrometer | Instrument for obtaining a spectrum of a star, galaxy, or astronomical object |
| Stefan-Boltzmann Law | Formula for which the rate at which a blackbody radiates energy can be computed; total rate of energy emission from a unit area of a blackbody is proportional to the fourth power of its absolute temperature |
| Ultraviolet | Electromagnetic radiation with wavelengths shorter than visible light |
| Visible Light | Electromagnetic radiation that can be seen |
| Wavelength | Distance from crest to crest or trough to trough in a wave |
| Wien's Law | Relates the temperature of a blackbody to the wavelength at which it emits the greatest intensity of radiation |
| X-Rays | Electromagnetic radiation between ultraviolet radiation and gamma rays |
| Adaptive Optics | Systems in telescopes that can compensate for distortions introduced by the atmosphere |
| Aperture | Diameter of the primary lens or mirror of a telescope |
| Charge-Coupled Device (CCD) | Array of high-sensitivity electronic detectors of electromagnetic radiation, used at the focus of a telescope to record an image or spectrum |
| Chromatic Aberration | Distortion that causes an image to appear fuzzy when each wavelength coming into a transparent material focuses at a different spot |
| Detector | Device sensitive to electromagnetic radiation that makes a record of astronomical observations |
| Eyepiece | Magnifying lens used to view the image produced by the objective lens or primary mirror of a telescope |
| Focus | Point where the rays of light converged by a mirror or lens meet |
| Interference | Process in which waves mix together such that their crests and troughs can alternately reinforce or cancel one another |
| Interferometer | Instrument that combines electromagnetic radiation from one or more telescopes to obtain a resolution equivalent wo what would be obtained with a single telescope with a diameter equal to the baseline separating the individual separate telescopes |
| Interferometer Array | Combination of radio dishes that works like a large number of two-dish interferometers |
| Objective Lens | Optical element that gathers light from the object being observed |
| Prime Focus | Point in a telescope where the objective lens or primary mirror focuses the light |
| Radar | Technique of transmitting radio waves to an object and then detecting the radiation that the object reflects back to the transmitter; used to measure distance to, and motion of, a target object or to form images of it |
| Refracting Telescope | Telescope in which the principal light collector is a lens or system of lenses |
| Reflecting Telescope | Telescope in which the principal light collector is a concave mirror |
| Resolution | Detail in an image |
| Seeing | Unsteadiness of Earth's atmosphere, which blurs telescopic images |
| Telescope | Instrument for collecting visible-light or other electromagnetic radiation |
| Asteroid | Stony or metallic object orbiting the Sun that is smaller than a major planet but that shows no evidence of an atmosphere or of other types of activity associated with comets |
| Comet | Small body of ice and dusty matter that revolves about the sun; when one comes near the Sun, some of its material vaporizes, forming a large head of gas and often a tail as well |
| Differentiation | Gravitational separation of materials of different density into layers in the interior of a planet |
| Giant Planet | Any of the planets Jupiter, Saturn, Uranus, and Neptune in our solar system, or planets of roughly that mass and composition in other planetary systems |
| Half-Life | Time required for half of the radioactive atoms in a sample to disintegrate |
| Meteor | Small piece of solid matter that enters Earth's atmosphere and burns up |
| Meteorite | Small piece of solid matter that survives passage through the atmosphere and strikes the ground |
| Meteoroid | Small piece of solid matter in space; smaller than an asteroid |
| Planetesimals | Objects, from tens to thousands of kilometers in diameter, that formed in the solar nebula as an intermediate step between tiny grains and larger planetary objects that we see today |
| Radioactivity | Process by which certain atomic nuclei decay, emitting subatomic particles and gamma rays |
| Solar Nebula | Cloud of gas and dust from which the solar system formed |
| Terrestrial Planet | Any of the planets Mercury, Venus, Earth, or Mars |
| Crater of Eternal Darkness | Depression on a body in the Solar System which lies in constant darkness |
| Highlands | Lighter, heavily cratered regions of the Moon; higher than the Maria |
| Lava Tubes | Natural conduits of flowing lava that move beneath the surface of the Earth |
| Lunar Dome | Type of shield volcano found on the surface of the Moon |
| Lunar Swirls | Features on the Moon's surface that reflect an unusually large amount of light |
| Maria | Dark, relatively smooth areas that cover seventeen percent of the Moon's surface |
| Peak of Eternal Light | Hypothetical point on the surface of an astronomical body that is always in sunlight |
| Rilles | Long, narrow depressions in the surface of the Moon that resemble channels |
| Wrinkle Edges | Ridges that develop on the surface of lunar maria |
| Runaway Greenhouse Effect | Process by which the Greenhouse Effect, rather than remaining stable or being lessened through intervention, continues to grow at an increasing rate |
| Tectonic | Geological features that result from stresses and pressures in the crust of a planet |
| Photochemistry | Chemical changes caused by electromagnetic radiation |
| Synchrotron Radiation | Radiation emitted by charged particles being accelerated in magnetic fields moving at speeds near that of light |
| Resonance | Orbital condition in which one object is subject to periodic gravitational perturbations by another, most commonly arising when two objects orbiting a third have periods of revolution that are simple multiples of each other |
| Tidal Heating | Heating of a planet's or moon's interior caused by gravitational pull from a nearby planet or moon |
| Coma | Nucleus around a comet, formed when part of the comet sublimates as it passes by the Sun |
| Kuiper Belt | Region of space beyond Neptune that is dynamically stable; the source region for most short-period comets |
| Near-Earth Asteroid (NEA) | Earth-approaching asteroid whose orbit could bring it on a collision course with our planet |
| Near-Earth Object (NEO) | Comet or asteroid whose path intersects the orbit of Earth |
| Nucleus | Solid chunk of ice and dust in the head of a comet |
| Oort Cloud | Large spherical region around the Sun from which "new" comets come |
| Tail | Dust and ions that follow a comet |
| Accretion | Gradual accumulation of mass, as by a planet forming from colliding particles in the solar nebula |
| Exoplanet | Planet orbiting a star other than out sun |
| Iron Meteorite | Meteorite composed primarily of iron and nickel |
| Meteor Shower | When many meteors appear to radiate from one point in the sky; produced when Earth passes through a cometary dust stream |
| Stony Meteorite | Meteorite composed mostly of stony material, either primitive or differentiated |
| Stony-Iron Meteorite | Type of differentiated meteorite that is a blend of nickel-iron and silicate materials |
| Active Region | Area on the Sun where magnetic fields are concentrated; sunspots, prominences, flares, and CMEs all tend to occur in these areas |
| Aurora | Light radiated by atoms and ions in the ionosphere excited by charges particles from the Sun; mostly seen in the magnetic polar regions; Borealis (north) and Australis (south) |
| Chromosphere | Part of the solar atmosphere that lies immediately above the phosophere |
| Corona | Outermost layer of the Sun's atmosphere; it has the highest temperatures |
| Coronal Hole | Region in the Sun's outer atmosphere that appears darker because there is less hot gas |
| Coronal Mass Ejection (CME) | Solar flare in which immense quantities of coronal material - mainly protons and electrons - are ejected at high speeds into interplanetary space |
| Differential Rotation | Phenomenon that occurs when different parts of a rotating object rotate at different latitudes |
| Fission | Breaking up of heavier atomic nuclei into lighter ones |
| Fusion | Building up of heavier atomic nuclei from lighter ones |
| Granulation | Rice-grain-like structure of the solar photosphere; produced by upwelling currents of gas that are slightly hotter, and therefore brighter, then the surrounding regions, which are flowing downward into the Sun |
| Helioseismology | Study of pulsations or oscillations of the Sun to determine the characteristics of the solar interior |
| Hydrostatic Equilibrium | Balance between the weights of various layers, as in a star of Earth's atmosphere, and the pressures that support them |
| Maunder Minimum | Period in the 18th century where the number of sunspots was unusually low |
| Neutrino | Elementary particle that has no charge and a mass that is almost zero; it is emitted from the sun and rarely interacts with ordinary matter |
| Photosphere | Region of the solar atmosphere from which continuous radiation escapes into space |
| Plage | Bright region of the chromosphere of the Sun |
| Plasma | Hot, ionized gas that is considered to be a fourth state of matter |
| Positron | Particle with the same mass as an electron, but positively charged |
| Prominence | Large, bright, gaseous feature that appears above the surface of the Sun and extends into the corona |
| Proton-Proton Chain | Series of thermonuclear reactions by which hydrogen nuclei are built into helium nuclei |
| Radiation | Emission of energy as electromagnetic waves or photons; also a term for the transmitted energy itself |
| Solar Flare | Sudden and temporary increase in the brightness of the Sun |
| Solar Wind | Flow of hot, charged particles leaving the Sun |
| Sunspot | Large, dark features seen on the surface of the Sun caused by increased magnetic activity |
| Sunspot Cycle | Semiregular eleven-year-period with which the frequency of sunspots flucuates |
| Transition Region | Region in the Sun's atmosphere where the temperature rises very rapidly from the relatively low temperatures that characterize the chromosphere to the high temperatures of the corona |
| Apparent Brightness | Measure of the amount of light received by Earth from a star or other object - that is, how bright an object appears in the sky, as contrasted with its luminosity |
| Brown Dwarf | Object intermediate in size between a planet and a star; its maximum mass is up to the lower mass limit for self-sustaining nuclear reactions; capable of deuterium fusion, but no hydrogen fusion |
| Color Index | Difference between the magnitudes of a star or other object measure in light of two different spectral regions - for example, Blue minus Visual (B-V) magnitudes |
| Giant | Star of exaggerated size with a large, extended photosphere |
| Luminosity | Rate at which a star or other object emits electromagnetic energy into space; contrasted with apparent brightness |
| Magnitude | Older system of measuring the amount of light we receive from a star or other object; the larger the number, the less radiation we receive from the object |
| Proper Motion | Angular change per year in the direction of a star as seen from the Sun |
| Space Velocity | 3D speed and direction with which an object is moving through space relative to the Sun |
| Spectral Class | Classification of stars according to their temperatures; the types are O, B, A, F, G, K, and M; the highest is O and the coolest is M; sometimes L, T, and Y are used |
| Binary Stars | Two stars that revolve about each other |
| Hertzsprung-Russell Diagram | H-R Diagram; plot of luminosity against surface temperature for a group of stars |
| Main Sequence Star | Star that is roughly on a diagonal line on the Hertzsprung-Russell Diagram; the line extends from the upper left to the lower right |
| White Dwarf | Low-mass star that has exhausted most or all of its nuclear fuel and has collapsed to a very small size; such a star is near its final state of life |
| Cepheid | Star that belongs to a class of yellow supergiant pulsating stars; these vary periodically in brightness, and the relationship between their periods and luminosities is useful in deriving distances to themq |
| Luminosity Class | Classification of a star according to its luminosity within a given spectral class; our Sun, a G2V, has luminosity class V |
| Parsec | Unit of distance equal to 3.26 light years; at a distance of one of these, a star has a parallax of one arcsecond. |
| Pulsating Variable Star | Variable star that pulsates in size and luminosity |
| RR Lyrae | One of a class of giant pulsating stars with periods shorter than one day, useful for finding distances |
| Variable Star | Star whose apparent magnitude fluctuates |
| Baryon Cycle | Cycling of mass in and out of interstellar matter, including accretion of gas from intergalactic space, loss of gas back into intergalactic space, and conversion of interstellar gas into stars |
| Cosmic Rays | Atomic nuclei and electrons that are observed to strike Earth's atmosphere with high energy |
| H II Region | Region of ionized hydrogen in interstellar space |
| Interstellar Dust | Tiny solid grains in interstellar space thought to consist of a core of rocklike material or graphite surrounded by mantles of ice; water, methane, and ammonia are probably the most abundant ices |
| Interstellar Extinction | Gradual loss of absorption of light by dust in the interstellar matter |
| Interstellar Matter | Gas and dust between the stars in a galaxy |
| Local Bubble | Region of low-density, million degree gas in which the Sun and solar system are currently located |
| Local Fluff | Slightly denser cloud inside the Local Bubble, inside which the Sun also lies |
| Molecular Cloud | Large, dense, cold interstellar cloud; because of its size and density, this type of cloud can keep ultraviolet radiation from reaching its interior, where molecules can form |
| Nebula | Cloud of interstellar gas or dust that glows with visible or infrared light |
| Reddening | Color change of starlight passing through interstellar dust because dust scatters blue light more effectively than red light |
| Giant Molecular Cloud | Large, cold, interstellar cloud with a diameter of dozens of light-years; found in the spiral arms of galaxies, they are often the sites of stellar formation |
| Mini-Neptune | Planet that is intermediate in size between the largest terrestrial planet in our solar system (Earth) and the smallest jovial planet (Neptune) |
| Protostar | Very young star still in the process of formation, before nuclear fusion begins |
| Stellar Wind | Outflow of gas, sometimes at speeds as high as hundreds of kilometers per second, from a star |
| Super-Earth | Any planet larger than Earth |
| Transit | When one astronomical object moves in front of another |
| Association | Loose group of young stars whose spectral types, motions, and positions in the sky indicate a common origin |
| Globular Cluster | One of about one hundred and fifty large, spherical star clusters that form a system of clusters in the center of our galaxy |
| Helium Flash | Runaway nuclear fusion of helium into carbon in low-mass red giants |
| Main-Sequence Turnoff | Location in the Hertzsprung-Russell Diagram where stars begin to leave the main sequence |
| Nucleosynthesis | Building up of heavy elements from lighter ones by nuclear fusion |
| Open Cluster | Comparatively loose cluster of stars, containing from a few dozen to a few thousand members, located in the spiral arms or disk of our Galaxy; |
| Planetary Nebula | Shell of gas ejected by and expanding away from an extremely hot low-mass star that is nearing the end of its life |
| Triple-Alpha Process | Nuclear reaction by which three helium nuclei are fused into one carbon nucleus |
| Zero-Age Main Sequence | Line denoting the main sequence on the H-R Diagram for a system of stars that are deriving all their energy from nuclear reactions, but whose chemical compositions has not yet been altered substantially by nuclear reactions |
| Chandrasekhar Limit | Upper limit to the mass of a white dwarf |
| Degenerate Gas | Gas that resists further compression due to the Pauli exclusion principle |
| Millisecond Pulsar | Pulsar that rotates so quickly that it can give off hundreds of pulses per second |
| Neutron Star | Compact star of extremely high density composed of almost entirely neutrons |
| Nova | Astronomical event that causes the sudden appearance of a bright, apparently "new" star, that slowly fades over several weeks or months |
| Pulsar | Variable radio source that emits rapid radio pulses in very regular periods; now understood to be rotating, magnetic, neutron stars that are energetic enough to produce a detectable beam of radiation and particles |
| Supernova | Powerful and luminous stellar explosion that occurs during the last evolutionary stages of a massive star or when a white dwarf is triggered into runaway nuclear fusion |
| Accretion Disk | Disk of gas and dust found orbiting newborn stars, white dwarfs, neutron stars, and black holes when they are in binary systems and are sufficiently close to their companions to draw off material |
| Black Hole | Region in spacetime where gravity is so strong that nothing - not even light - can escape it |
| Equivalence Principle | Concept that a gravitational force and a suitable acceleration are indistinguishable within a sufficiently local environment |
| Event Horizon | Boundary in spacetime such that events inside the boundary can have no effect on the world outside it; the boundary of a black hole where the curvature of spacetime no longer provides any way out |
| Gravitational Wave | Disturbance in the curvature of spacetime caused by changes in how matter is distributed; they propagate at or near the speed of light |
| Singularity | Point of zero volume and infinite density to which any object that becomes a black hole must collapse, according to the theory of general relativity |
| Spacetime | System of one time and three space coordinates, with respect to which the time and place of an event can be specified |
| Central Bulge | Central, round part of the Milky Way or a similar galaxy |
| Dark Matter | Nonluminous mass whose presence can be inferred only because of its gravitational influence on luminous matter; it is thought to account for almost ninety percent of the matter in the universe |
| Differential Galactic Rotation | Idea that different parts of the Galaxy turn at different rates, since the parts of the Galaxy follow Kepler's third law; the more distant objects take longer to complete one full orbit around the center of the Galaxy |
| Halo | Outermost extent of our Galaxy, containing a spare distribution of stars and globular clusters in a more or less spherical distribution |
| Milky Way Galaxy | Galaxy in which Earth resides |
| Population I Star | Star containing heavy elements, typically young and found in the disk |
| Population II Star | Star with very low abundance of heavy elements |
| Spiral Arm | Spiral-shaped region, characterized by relatively dense interstellar material and young stars, that is observed in the disks of spiral galaxies |
| Supermassive Black Hole | Object in the center of most large galaxies that is so massive and compact that light cannot escape from it |
| Active Galaxy | Galaxy that houses an active galactic nucleus, which is a compact region at the center of the galaxy that has a much higher-than-normal luminosity not produced by stars |
| Elliptical Galaxy | Galaxy whose shape is an ellipse and contains no conspicuous interstellar material |
| Hubble's Law | Radial velocities of remote galaxies are proportional to their distances from us |
| Irregular Galaxy | Galaxy that is neither elliptical nor spiral; has no clear symmetry or pattern |
| Redshift | Change in wavelength due to an object moving away from the observer |
| Spiral Galaxy | Flattened, rotating galaxy with pinwheel-like arms of interstellar material and young stars, winding out from its central bulge |
| Cold Dark Matter | Slow-moving massive particles, not yet identified, that don't absorb, emit, or reflect light or other electromagnetic radiation |
| Cosmological Principle | Assumption that, on the large scale, the universe at any given time is the same everywhere - both isotropic and homogenous |
| Dark Energy | Energy that is causing the expansion of the universe to accelerate; the source of this energy is not yet understood or identified |
| Evolution | Changes in individual galaxies over cosmic time, inferred by observing snapshots of many different galaxies at different times in their lives |
| Galactic Cannibalism | Process where a large galaxy strips material from or completely swallows a smaller galaxy |
| Homogenous | Having a consistent and even distribution of matter that is the same everywhere |
| Hot Dark Matter | Fast-moving massive particles, not yet identified, that don't absorb, emit, or reflect light or other electromagnetic radiation |
| Isotropic | Same in all directions |
| Local Group | Small cluster of galaxies to which our galaxy belongs |
| Merger | Collision between galaxies that combine to form a new structure |
| Starbust | Galaxy or merger of multiple galaxies that turns gas into stars much faster than usual |
| Supercluster | Large region of space where groups and clusters of galaxies are more concentrated; a cluster of clusters of galaxies |
| Void | Region between clusters and superclusters of galaxies that appears relatively empty of galaxies |
| Anthropic Principle | |
| Big Bang | |
| Big Crunch | |
| Closed Universe | |
| Cosmic Microwave Background | |
| Cosmology | |
| Critical Density | |
| Flat Universe | |
| Grand Unified Theories | |
| Inflationary Universe | |
| Multiverse | |
| Open Universe | |
| Photon Decoupling Time | |
| Astrobiology | |
| Biomarker | |
| Drake Equation | |
| Extremophile | |
| Fermi Paradox | |
| Habitable Environment | |
| Habitable Zone | |
| SETI | |
| Stromatolites | |
| Thermophile | |
| Perseids | |
| Orionids | |
| Geminids | |
| Van Allen Belts | |
| Hubble Space Telescope | |
| Arecibo Observatory | |
| Mercury | |
| Venus | |
| Mars | |
| Jupiter | |
| Saturn | |
| Uranus | |
| Neptune | |
| Pluto | |
| Sun | |
| Laika | |
| Sputnik I | |
| Explorer I | |
| Yuri Gagarin | |
| Alan Shepard | |
| John Glenn | |
| Alexi Leonov | |
| Ed White | |
| Valentina Tereshkova | |
| Sally Ride | |
| Guion Bluford | |
| Neil Armstrong, Buzz Aldrin, Michael Collins | |
| Mercury Program | |
| Gemini Program | |
| Apollo Program | |
| Skylab Program | |
| Space Shuttle Program | |
| Vostok Program | |
| Vokshod Program | |
| Soyuz Program | |
| Salyut Program | |
| Virgil "Gus" Grissom, Ed White, Roger Chaffee | |
| Quasar |
Created by:
MarioValento
Popular Quiz Bowl sets