Astronomy 310 terms – Flashcards
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Universe
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The totality of all space, time, matter, and energy
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Astronomy
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Branch of science dedicated to the study of everything in the universe that lies above Earth's atmosphere
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Theory
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A framework of ideas and assumptions used to explain observations and make predictions about the real world
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Theoretical Model
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An attempt to construct a mathematical explanation of a physical process of phenomenon, within the assumptions and confines of a given theory
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Scientific Method
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The set of rules used to guide science, based on the idea that scientific "laws" be continually tested, and modified or replaced if found inadequate
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Constellation
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A human grouping of stars in the night sky into a recognizable pattern
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Celestial Sphere
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Imaginary sphere surrounding Earth to which all objects in the sky were once considered to be attached
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Rotation
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Spinning motion of a body about an axis
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Celestial Poles
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Projection of Earth's North or South pole onto the celestial sphere
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Solar day
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The period of time between noon and the next noon
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Sidereal Day
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The time needed between successive risings of a given star
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Revolution
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Orbital motion of one body about another
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Ecliptic
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The apparent path of the sun, relative to the stars on the celestial sphere, over the course of a year
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Zodiac
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The 12 constellations on the celestial sphere through which the Sun appears to pass during the course of a year
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Summer Solstice
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Point when the Sun is most north occurring on June 21
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Winter Solstice
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Point when the Sun is most south occurring on December 21
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Seasons
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Changes in average temperature and length of day that result from the tilt of the Earth's axis
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Autumnal equinox
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When the Sun crosses the celestial equator moving south, occurring on September 21
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Vernal equinox
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When the Sun crosses the celestial equator moving north, occurring on March 21
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Tropical year
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The time interval between one vernal equinox and the next
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Precession
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The slow change in the direction of the rotation axis of a spinning object
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Sidereal Year
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The time required for the constellations to complete one cycle around the sky/Earth's orbital period around the Sun
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Phases
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Appearance of the sunlit face of the Moon at different points along it's orbit, as seen from Earth
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Sidereal month
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Time required for the Moon to complete one trip around the celestial sphere
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Synodic Month
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Time required for the Moon to complete a full cycle of phases
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Partial eclipse
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Celestial event during which only a part of the body is blocked from view
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Lunar eclipse
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Celestial event during which the moon passes through the shadow of Earth, temporarily darkening its surface
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Total eclipse
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Celestial event during which one body is completely blocked from view by another
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Solar Eclipse
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Celestial event during which the new Moon passes directly between Earth and the Sun, temporarily blocking the Sun's light
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Umbra
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Central region of the shadow cast by an eclipsing body which is its darkest and coolest part
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Penumbra
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The outer region of a sunspot which is not as dark and not as cool as the central region
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Annular eclipse
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Solar eclipse occurring at a time when the Moon is far enough away from Earth that it fails to cover the disk of the sun completely, leaving a ring of sunlight visible around its edge
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Eclipse season
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Time of the year when the moon lies in the same plane as Earth and Sun, so that eclipses are possible
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Triangulation
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Method of determining distance by finding two well separated locations and measuring the angle between the line joining them and the line to the distant object
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Cosmic distance scale
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Collection of indirect distance-measurement techniques that astronomers use to measure distances in the universe
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Baseline
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The distance between two observing locations used for the purposes of triangulation measurements
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Parallax
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The apparent motion of a relatively close object with respect to a more distant background as the location of the observer changes
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Retrograde Motion
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Backward, westward loop traces out by a planet with respect to the fixed stairs
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Geocentric model
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A model of the solar system that holds that Earth is at the center of the universe and all other bodies are in orbit around it
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Epicycle
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The small revolution about an imaginary point that each planet makes in the geocentric model of the solar system.
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Deferent
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A large circle encircling Earth, on which an epicycle moves in the geocentric model of the solar system
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Ptolemaic Model
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Geocentric solar system model that predicted the positions of the then known planets
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Heliocentric model
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A model of the solar system that is centered on the Sun, with Earth in motion about the Sun
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Copernican revolution
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The realization that the Earth is not at the center of the universe
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Aberration of starlight
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Small shift in the observed direction to a star, caused by Earth's motion perpendicular to the line of sight
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Ellipse
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An elongated circle characterized by its eccentricity and the length of its long axis
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Focus
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One of two special points within an ellipse, whose separation from each other indicates the eccentricity. The closer the two points, the less eccentricity.
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Semimajor axis
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One-half of the major axis of an ellipse
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Eccentricity
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A measure of the flatness of an ellipse, equal to the distance between the two foci divided by the length of the major axis
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Period
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The time needed for an orbiting body to complete one revolution about another body
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Astronomical Unit
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The average distance of Earth from the sun
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Radar
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Acronym for radio detection and ranging
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Newtonian mechanics
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The basic laws of motion
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Weight
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The gravitational force exerted on you by Earth
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Force
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Action on an object that causes its momentum to change
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Inertia
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The tendency of an object to continue moving at the same speed and in the same direction, unless acted upon by a force
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Mass
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A measure of the total amount of matter contained within an object
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Velocity
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wavelength/period
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Acceleration
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The rate of change of velocity
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Gravity
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The attractive effect that any massive object has on all other objects
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Gravitational Force
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Force exerted on one body by another due to the effect of gravity that is directly proportional to the masses of both bodies involved and inversely proportional to the square of the distance between them
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Inverse-square law
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The law that a field's strength decreases as the distance increases.
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Escape speed
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The speed necessary for one object to escape the gravitational pull of another. Anything that moves away from a gravitating body with more than the escape speed will never return
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Solar System
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The sun and all the bodies that orbit it - Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune, their moons, the asteroids, the comets, and trans-Neptunian objects
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Comparative Planetology
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The systematic study of the similarities and differences among the planets
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Density
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A measure of the compactness of the matter within an object
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Terrestrial Planets
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One of the four most innermost planets of the solar system, resembling Earth in general physical and chemical properties. Low mass, small size, high density, few moons.
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Jovian Planets
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The four giant outer planets of the solar system, resembling Jupiter in physical and chemical composition. High mass, large size, low density, many moons.
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Interplanetary Matter
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Matter in the solar system that is not part of a planet or moon - cosmic "debris"
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Gravity Assist
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Using gravity to change the flight path of a satellite or spacecraft
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Solar Nebula
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The swirling gas surrounding the early Sun during the epoch of solar system formation, also referred to as the primitive solar system
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Nebular Theory
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One of the earliest models if solar system formation, dating back to Descartes, in which a large cloud of gas began to collapse under its own gravity to form the Sun and planets
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Condensation Theory
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Currently favored model of solar system formation which combines features of the old nebular theory with new information about interstellar dust grains, which acted as condensation nuclei
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Angular Momentum
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Tendency of an object to keep rotating; proportional to the mass, radius, and rotation speed of the body
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Condensation Nuclei
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Dust grains in the interstellar medium which act as seeds around which other material can cluster. The presence of dust was very important in causing matter to clump during the formation of the solar system
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Accretion
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Gradual growth of bodies, such as planets, by the accumulation of other smaller bodies
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Planetesimal
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Term given to objects in the early solar system that had reached the size of small moons, at which point their gravitational fields were strong enough to begin influencing their neighbors
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Protoplanet
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Clump of material, formed in the early stages of solar system formation, that was the forerunner of the planets we see today
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Fragmentation
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The breaking up of a large object into many smaller pieces (for example, as the result of high-speed collisions between planetesimals and protoplanets in the early solar system)
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Protosun
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The central accumulation of material in the early stages of solar system formations, the forerunner of the present-day Sun
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Super-Earth
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Extrasolar planet with mass between 2 and 10 Earth masses. Both rocky and oceans have been detected
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Hot Jupiter
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A massive, gaseous planet orbiting very close to its parent star
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Selection Effect
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Observational bias in which a measured property of a collection of objects is due to the way in which the measurement was made, rather than being intrinsic to the objects themselves
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Brown Dwarf
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Fragments of collapsing gas and dust that did not contain enough mass to initiate core nuclear fusion. It is frozen and continues to cool into a compact dark object. Small size and low temperature.
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Cosmic Evolution
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The collection of the seven major phases of the history of the universe - namely particulate, galactic, stellar, planetary, chemical, biological, and cultural evolution
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Amino Acids
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Organic molecules that form the basis for building the proteins that direct metabolism in living creatures
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Nucleotide Bases
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An organic molecule, that passes on hereditary characteristics from one generation to the next
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Urey Miller experiment
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Groundbreaking experiment that simulated conditions on the early Earth and tested for the occurrence of chemical evolution
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Extremophilic
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Adjective describing organisms that can survive in very harsh environments
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Drake Equation
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Expression that gives an estimate of the probability that intelligence exists elsewhere in the Galaxy
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SETI
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Acronym for search for extraterrestrial intelligence
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Water hole
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The radio interval between 18cm and 21cm, the respective wavelengths at which OH and H radiate, in which intelligent civilizations might conceivably send their communication signals
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Electromagnetic Radiation
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Another term for light, transfers energy and information from one place to another
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Wein's law
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The hotter the object, the bluer it gets
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Stefan's law
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total energy emission is proportional to temperature to the exponent 4
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Radio
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Wavelengths are longest and include microwave, AM/FM, and TV bands
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Infrared
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Wavelengths long and associated mainly with heat
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Visible Light
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Wavelengths that we can see with the naked eye. Red has the longest to violet with the shortest
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Ultraviolet
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Wavelengths shorter and associated with sunburns and suntans
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Waves
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A pattern that repeats itself cyclically and characterized by the speed they move, frequency, and length
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X-ray
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Wavelengths short and associated with being able to penetrate human skin
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Wavelength
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The distance from one wave crest (or trough) to the next
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Gamma ray
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Wavelengths shortest and deadly to living cells
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Amplitude
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The distance between the top and zero line of a wave
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Frequency
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The number of wave crests passing a given point in a unit time
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Proton
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An elementary particle carrying a positive electric charge
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Electron
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An elementary particle carrying a negative electric charge
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Electric field
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A field extending outward in all directions from a charged particle
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Magnetic field
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Field that accompanies any changing electric field
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Electromagnetism
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The union of electricity and magnetism in a single phenomenon (never individually)
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Wave theory of radiation
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Description of light as a continuous wave phenomenon, rather than as a stream of individual particles
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Electromagnetic spectrum
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The complete range of electromagnetic radiation, from radio to gamma rays.
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Opacity
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A quantity that measures a material's ability to block radiation
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Diffraction
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The ability of waves to bend around corners
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Interference
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The ability of two or more waves to interact in such a way that they either reinforce or cancel each other
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Temperature
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A measure of the amount of heat in an object
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Blackbody Curve
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The intensity of radiation emitted by a hot object depends on frequency
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Doppler effect
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Any motion-induced change in the observed wavelength of a wave
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Asteroid belt
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Region of the solar system, between the orbits of Mars and Jupiter, in which most asteroids are found
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Earth-crossing asteroid
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An asteroid who's orbit crosses that of earth
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Trojan asteroid
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One of two groups of asteroids which orbit at the same distance from the sun as Jupiter
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Kirkwood gaps
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Gaps in the spacings of orbital semimajor axes of asteroids in the asteroid belt, produced by nearby planets, especially Jupiter
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Comet
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A small body, composed mainly of ice and dust, in an elliptical orbit around the sun
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Nucleus
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Dense, central region of an atom, containing both protons and neutrons, and orbited by one or more electrons
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Coma
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The appearance of a comet-like tail on stars on the image in a telescope
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Tail
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Dust and ionized gas that stream away from the body of a comet
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Hydrogen envelope
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An invisible sheath of gas engulfing the coma of a comet, usually distorted by the solar wind
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Ion tail
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Ionized gas that is pushed away from the head of a comet by the solar wind and extends directly away from the sun
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Dust tail
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The component if a comet's tail that is composed of dust particles
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Kuiper belt
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A region in the plane of the solar system outside the orbit of Neptune where most short-period comets are thought to originate
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Oort cloud
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Halo of material surrounding the solar system
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Kuiper belt object
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Small icy body orbiting in the Kuiper belt
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Trans-neptunian object
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A small, icy body orbiting beyond the orbit of Neptune
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Dwarf planet
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A body that orbits the Sun and is big enough that its own gravity has caused its shape to be approximately spherical, but not big enough to have cleared out the area
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Plutoid
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A dwarf planet orbiting beyond Neptune
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Meteor
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Bright steak in the sky resulting from interplanetary debris entering Earth's atmosphere. Comes from a comet.
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Meteoroid
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Chunk of interplanetary debris prior to entering Earth's atmosphere. Comes from an asteroid.
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Meteoroid swarm
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Pebble-sized fragments dislodged from a comet, moving in nearly the same orbit as the parent comet
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Micrometeoroid
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Small chunk of interplanetary debris ranging in size from a dust particle to a pebble
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Meteor shower
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Event during which many meteors can be seen in an hour
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Meteorite
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Any part of a meteoroid that survives passage through the Earth's atmosphere
