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Astronomy Final

Tides The deformation of a mass due to differential gravitational effects of one mass on another because of the extended size of the masses, On Earth- the rise and fall of the oceans as Earth rotates through a tidal bulge caused by the Moon and Sun
Self- Gravity The gravitational attraction among all the parts of the same object
Spherically Symmetric Describing an object whose properties depend only on distance from the object’s center, so that the object has the same form viewed from any direction
Symmetry The property that an object has if the object is unchanged by rotation or reflection about a particular point, line, or plane
Tidal Stresses Stress due to differences in the gravitational force of one mass on different parts of another mass
Lunar Tides A tide on Earth that is due to the differential gravitational pull of the Moon
Tidal Bulge A distortion of a body resulting fro tidal stresses
Solar Tides A tide on Earth that is due to the differential gravitational pull of the Sun
Spring Tides An especially strong tide that occurs near the time of a new or full Moon, where lunar tides and solar tides reinforce each other
Neap Tides An especially weak tide that occurs around the time of the first or third-quarter Moon when the gravitational forces of the Moon and the Sun on Earth are at right angles to each other, thus producing the least pronounced tides
Synchronous Rotation The case in which the period of rotation of a body on its axis equals the period of revolution in its orbit around another body, A special type of spin-orbit resonance
Tidal Locking Synchronous rotation of an object caused by internal friction a the object rotates through its tidal bulge
Libration The apparent wobble of an orbiting body that is tidally locked to its companion (such as Earth’s Moon) resulting from the fact that its orbit is elliptical rather than circular
Spin-Orbit Resonance A relationship between the orbital and rotation periods of an object such that the ratio of their periods can be expressed by simple integers
Roche Limit The distance at which a planet’s tidal forces exceed the self-gravity of a smaller object, such as a moon, asteroid, or comet, causing the object to break apart
Kirkwood Gaps A gap in the main asteroid belt related to orbital resonances with Jupiter
Orbital Resonance A situation in which the orbital periods of two objects are related by a ratio of small integers
Cassini Division The largest gap in Saturn’s rings, discovered by Jean-Dominique Cassini in 1675
Shepherd Moons A moon that orbits close to rings and gravitationally confines the orbits of the ring particles
Lagrangian Equilibrium Points One of five points of equilibrium in a system consiting of two massive objects in nearly circular orbit around a common center of mass, Only two Lagrangian points (4 and 5) represent stable equilibrium, A third smaller body located at one of the five poin
Trojan Asteroids One of a group of asteroids orbiting in the 4 and 5 Lagrangian points of Jupiter’s orbit
Chaos Behavior in complex, interrelated systems in which tiny differences in the initial configuration of a system result in dramatic differences in the system’s later evolution
Complex System An interrelated system capable of exhibiting chaotic behavior
Regular Moon A moon that formed together with the planet it orbits
Irregular Moon A moon that has been captured by a planet, Some irregular moons revolve in the opposite direction from the rotation of the planet, and many are in distant, unstable orbits
Retrograde Motion Rotation or orbital motion of a moon that is I the opposite sense to the rotation of the planet it orbits
Cryovolcanism Low-temperature volcanism in which the magmas are composed of molten ices rather than rocky material
Photodissociation The breaking apart of molecules into smaller fragments or individual atoms by the action of photons
Ring An aggregation of small particles orbiting a planet or star, The rings of the four giant planets of the Solar System are composed variously of silicates, organic materials, and ices
Ring Arcs A discontinuous, higher-density region within an otherwise continuous narrow ring
Ringlets A narrow confined concentration of ring particles
Diffuse Rings A sparsely populated planetary ring spread out both horizontally and vertically
Backlighting Illumination from behind a subject as seen by an observer, Fine material such as human hair and dust in planetary rings stands out best when viewed under backlighting conditions
Electromagnetic Forces The force, including both electric and magnetic forces, that acts on electrically charged particles, One of four fundamental forces of nature, The force mediated by photons
Spokes One of several narrow radial features seen occasionally in Saturn’s B ring, Spokes appear dark in backscattered light and bright in forward, scattering light, indicating that they are composed of tiny particles, Their origin Is not well understood
Planetesimals A primitive body of rock and ice, 100 meters or more in diameter, that combines with others to form a planet
Dwarf Planets A body with characteristics similar to those of a classical planet except that it has not cleared smaller bodies from the neighboring regions around its orbit
Asteroids A primitive rocky or metallic body (planetesimal) that has survived planetary accretion, Asteroids are parent bodies of meteoroids
Comet Nuclei A primitive planetesimal, composed of ices and refractory materials, that has survived planetary accretion, the “heart” of a comet, containing nearly the entire mass of the comet, a “dirty snowball”
Kuiper Belt Objects (KBOs) An icy planetesimal (comet nucleus) that orbits within the Kuiper Belt beyond the orbit of Neptune
Oblateness The flatness of an otherwise spherical planet or star caused by its rapid rotation
Comet A complex object consisting of a small, solid, icy nucleus; an atmospheric halo; and a tail of gas and dust
Meteorites A meteoroid that survives to reach a planet’s surface
Meteoroid A small cometary or asteroidal fragment ranging in size from 100 micrometers to 100 meters, When entering a planetary atmosphere, the meteoroid creates a meteor, which is an atmospheric phenomenon
Meteor The incandescent trail produced by a small piece of interplanetary debris as it travels though the atmosphere at very high speeds
Stony Meteorites A meteorite composed primarily of silicate minerals, similar to those found on Earth
Chondrules A small, crystallized, spherical inclusion of rapidly cooled molten droplets found inside some meteorites
Chondrites A stony meteorite containing chondrules
Carbonaceous Chondrites A primitive stony meteorite that contains chondrules and is rich in carbon and volatile materials
Achondrites A stony meteorite that does not contain chondrules
Iron Meteorites A metallic meteorite composed mostly of iron-nickel alloys
Stony-Iron Meteorites A meteorite consisting of a mixture of silicate minerals and iron-nickel alloys
C-type Asteroids An asteroid made of material that has largely been unmodified since the formation of the Solar System; the most primitive type of asteroid
S-type Asteroids An asteroid made of material that has been modified from its original state, likely as the outer part of a larger, differentiated body that has since broken into pieces
M-type Asteroids An asteroid that was once part of the metallic core of a larger, differentiation body that has since been broken into pieces; made mostly of iron and nickel
Main Asteroid Belt The region between the orbits of Mars and Jupiter that contains most of the asteroids in our Solar System
Near-Earth Asteroids An asteroid whose orbit brings it close to the orbit of Earth
Amors A group of asteroids whose orbits cross the orbit of Mars but not the orbit of Earth
Atens A group of asteroids whose orbits cross the orbit of Earth but not the orbit of Mars
Apollos A group of asteroids whose orbits cross the orbits of both Earth and Mars
Near-Earth Objects (NEOs) An asteroid, comet, or large meteoroid whose orbit intersects Earth’s orbit
Active Comets A comet nucleus that approaches close enough to the Sun to show signs of activity, such as the production of a coma and tail
Kuiper Belt A disk-shaped population of comet nuclei extending from Neptune’s orbit to perhaps several thousand astronomical units (AU) from the Sun, The highly populated innermost part of the Kuiper Belt has an outer edge approximately 50 AU from the Sun
Oort Cloud A spherical distribution of comet nuclei stretching from beyond the Kuiper Belt to more than 50,000 astronomical units (AU) fro the Sun
Nucleus The central core of a galaxy, comet, or other diffuse object
Sublimation The process in which a solid becomes a gas without first becoming a liquid
Coma The nearly spherical cloud of gas and dust surrounding the nucleus of an active comet
Tail A stream of gas and dust swept away from the coma of a comet by the solar wind and by radiation pressure from the Sun
Ion Tail A type of comet tail consisting of ionized gas, Particles in the ion tail are pushed directly away from the comet’s head in the antisolar direction at high speeds by the solar wind
Dust Tail A type of comet tail consisting of dust particles that are pushed away from the comet’s head by radiation pressure from the Sun
Perihelion The point in a solar orbit that is closest to the Sun
Short-Period Comets A comet with an orbital period of less than 200 years
Long-Period Comets A comet with an orbital period of greater than 200 years
Prograde Motion Rotational or orbital motion of a moon that is in the same sense as the planet it orbits
Aphelion The point in a solar orbit that is farthest from the Sun
Sungrazers A comet whose perihelion is within a few solar diameters of the surface of the Sun
Bolide A very bright, exploding meteor
Sporadic Meteors A meteor that is not associated with a specific meteor shower
Meteor Shower A larger-than-normal display of meteors, occurring when Earth passes through the orbit of a disintegrating comet, sweeping up its debris
Perseids A prominent August meteor shower associated with the dust debris left by comet Swift-Tuttle
Radiant The direction in the sky from which the meteors in a meteor shower seem to come
Leonids A November meteor shower associated with the dust debris left by comet Tempel-Tuttle
Zodiacal Dust Particles of cometary and asteroidal debris less than 100 micrometers in size that orbit the inner Solar System close to the plane of the ecliptic
Zodiacal Light A band of light in the night sky caused by sunlight reflected by zodiacal dust
Strong Nuclear Force The attractive short-range force between protons and neutrons that holds atomic nuclei together; one of the found fundamental forces of nature, mediated by the exchange of gluons
Nuclear Fusion The combination of two less massive atomic nuclei into a single more massive atomic nucleus
Hydrogen Burning The release of energy from the nuclear fusion of four hydrogen atoms into a single helium atom
Core The innermost part/region of a star/planetary interior
Energy Transport The transfer of energy from one location to another, In stars, energy transport is carried out mainly by radiation or convection
Thermal Conduction The transfer of energy in which the thermal energy of particles is transferred to adjacent particles by collisions or other interactions, Conduction is the most important way that thermal energy is transported in solid matter
Proton-Proton Chain One of the ways in which hydrogen burning can take place, This is the most important path for hydrogen burning in low-mass stars such as the Sun
Positron A positively charged subatomic particle; the antiparticle of the electron
Neutrino A very low-mass, electrically neutral particle emitted during beta decay, Neutrinos interact with matter only very feebly and so can penetrate through great quantities of matter
Beta Decay The decay of a proton into a neutron by emission of a positron and a neutrino
Antiparticle An elementary particle of anti-matter identical in mass by opposite in charge and all other properties to its corresponding ordinary matter particle
Nuclear Burning Release of energy by fusion of low-mass elements
Radiative Transfer The transport of energy from one location to another by electromagnetic radiation
Opacity A measure of how effectively a material blocks the radiation going through it
Radiative Zone A region in the interior of a star though which energy is transported outward by radiation
Convection The transport of thermal energy from lower (hotter) to the higher (cooler) layers of a fluid by motions within the fluid driven by variations in buoyancy
Convective Zone A region within a star in which energy is transported outward by convection
Solar Neutrino Problem The historical observation that only about a third as many neutrinos as predicted by theory seemed to be coming from the Sun
Photosphere The apparent surface of the Sun as seen in visible light
Effective Temperature The temperature at which a black body, such as a star, appears to radiate
Limb Darkening The darker appearance caused by increased atmospheric absorption near the limb of a planet or star
Atmosphere The gravitationally bound, outer gaseous envelope surrounding a planet, moon, or star
Chromosphere The region in the Sun’s atmosphere located between the photosphere and the corona
Corona The hot, outermost part of the Sun’s atmosphere
Coronal Holes A low-density region in the solar corona containing “open” magnetic field lines along which coronal material is free to stream into interplanetary space
Solar Wind The stream of charged particles emitted by the un that flows at high speeds through interplanetary space
Interstellar Medium The gas and dust that fill the space between the stars within a galaxy
Sunspots A cooler, transitory region on the solar surface produced when loops of magnetic flux break through the surface of the Sun
Differential Rotation Rotation of different parts of a system at different rates
Umbra The darkest, innermost part of a sunspot
Penumbra The region surround the umbra of a spot, The penumbra is cooler and darker than the surrounding surface of the Sun but not as cool or dark as the umbra of the sunspot
Sunspot Cycle The approximate 11-year cycle during which sunspot activity increases and then decreases, This is one-half of a full 22-year cycle, in which the magnetic polarity of the Sun first reverses and then returns to its original configuration
Maunder Minimum The period fro 1645 to 1715, when very few sunspots were observed
Solar Maxima The time, occurring about every 11 years, when the Sun is at its peak activity, meaning that sunspot activity and related phenomena (such as prominences, flares, and coronal mass ejections) are at their peak
Prominences An archlike projection above the solar photosphere often associated with a sunspot
Solar Flare Explosive events on the Sun’s surface associated with complex sunspot groups and strong magnetic fields
Plasma A gas that is composed largely of charged particles but also may include some neutral atoms
Coronal Mass Ejections An eruption on the Sun that ejects hot gas and energetic particles at much higher speeds than are typical in the solar wind
Mutation In biology, an imperfect reproduction of self-replicating material
Heredity The process by which one generation passes on its characteristics to future generations
Natural Selection The process by which forms of structure, ranging from molecules to whole organisms, that are best adapted to their environment become more common than less well-adapted forms
Entropy A measure of the disorder of a system related to the number of ways a system can be rearranged without its appearance being affected
Second Law of Thermodynamics The law stating that the entropy or disorder of an isolate system always increases as the system evolves
Astrobiology An interdisciplinary science combining astronomy, biology, chemistry, geology, and physics to study life in the cosmos
Habitable Zone The distance from its star at which a planet must be located in order to have a temperature suitable for life; often assumed to be temperatures at which water exists in a liquid state
Drake Equation A prescription for estimating the number of intelligent civilizations existing somewhere
SETI The Search for Extraterrestrial Intelligence project, which uses advanced technology combined with radio telescopes to search for evidence of intelligent life elsewhere in the universe
Created by: patrickofoz