English dictionary of Astronomy

English dictionary of Astronomy

English dictionary of Astronomy

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aberrance ; aberrancy ; aberration ; deviance
a state or condition markedly different from the norm

absolute magnitude
(astronomy) the magnitude that a star would have if it were viewed from a distance of 10 parsecs (32.62 light years) from the earth

acceleration ; quickening ; speedup
the act of accelerating; increasing the speed

albedo ; reflective power
the ratio of reflected to incident light

analogue ; parallel
something having the property of being analogous to something else

anomaly ; anomalousness
deviation from the normal or common order or form or rule

matter consisting of elementary particles that are the antiparticles of those making up normal substances

apogee ; culmination
a final climactic stage; "their achievements stand as a culmination of centuries of development"

Apollo program
a program of space flights undertaken by US to land a man on the Moon; "the first lunar landing was achieved by the Apollo program on July 20, 1969"

the appearance of a ghostlike figure; "I was recalled to the present by the apparition of a frightening specter"

a characteristic to be considered

any of numerous small celestial bodies composed of rock and metal that move around the sun (mainly between the orbits of Mars and Jupiter)

asteroid belt
the region of interplanetary space between Mars and Jupiter where most asteroids are found

an early form of sextant

the branch of astronomy that deals with the measurement of the position and motion of celestial bodies

astronaut ; spaceman ; cosmonaut
a person trained to travel in a spacecraft; "the Russians called their astronauts cosmonauts"

a physicist who studies astronomy

astronomic ; astronomical
relating or belonging to the science of astronomy; "astronomic telescope"

astronomy ; uranology
the branch of physics that studies celestial bodies and the universe as a whole

the branch of astronomy concerned with the physical and chemical properties of celestial bodies

a unit of pressure: the pressure that will support a column of mercury 760 mm high at sea level and 0 degrees centigrade

atmosphere ; air
the mass of air surrounding the Earth; "there was great heat as the comet entered the atmosphere"; "it was exposed to the air"

atmosphere ; ambience
a particular environment or surrounding influence; "there was an atmosphere of excitement"

atmospheric ; atmospherical
relating to or located in the atmosphere; "atmospheric tests"

aureole ; corona
the outermost region of the sun's atmosphere; visible as a white halo during a solar eclipse

aureole ; halo ; nimbus
an indication of radiant light drawn around the head of a saint

an atmospheric phenomenon consisting of bands of light caused by charged solar particles following the earth's magnetic lines of force

autumn ; fall
the season when the leaves fall from the trees; "in the fall of 1973"

science and technology of electronic systems and devices for aeronautics and astronautics; "avionics has become even more important with the development of the space program"

axis ; axis of rotation
the center around which something rotates

azimuth ; AZ
the azimuth of a celestial body is the angle between the vertical plane containing it and the plane of the meridian

beam ; ray ; shaft
a column of light (as from a beacon)

an elongated region where a specific condition or characteristic is found; "a belt of high pressure"

big bang
(cosmology) the cosmic explosion that is hypothesized to have marked the origin of the universe

binary star ; double star
a system of two stars that revolve around each other under their mutual gravitation

black hole
a region of space resulting from the collapse of a star; extremely high gravitational field

bulk ; volume
the property of something that is great in magnitude; "it is cheaper to buy it in bulk"; "he received a mass of correspondence"; "the volume of exports"

an abundant nonmetallic tetravalent element occurring in three allotropic forms: amorphous carbon and graphite and diamond; occurs in all organic compounds

celestial ; heavenly
relating to or inhabiting a divine heaven; "celestial beings"; "heavenly hosts"

celestial equator ; equinoctial circle
the great circle on the celestial sphere midway between the celestial poles

celestial mechanics
the branch of astronomy concerned with the application of Newton's laws of motion to the motions of heavenly bodies

celestial navigation ; astronavigation
navigating according to the positions of the stars

centrifugal force
the outward force on a body moving in a curved path around another body

a gaseous layer of the sun's atmosphere (extending from the photosphere to the corona) that is visible during a total eclipse of the sun

climate ; clime
the weather in some location averaged over some long period of time; "the dank climate of southern Wales"; "plants from a cold clime travel best in winter"

cluster ; bunch ; clump
a grouping of a number of similar things; "a bunch of trees"; "a cluster of admirers"

having a low or inadequate temperature or feeling a sensation of coldness or having been made cold by e.g. ice or refrigeration; "a cold climate"; "a cold room"; "dinner has gotten cold"; "cold fingers"; "if you are cold, turn up the heat"; "a cold beer"

cold ; coldness ; frigidness
the absence of heat; "the coldness made our breath visible"; "come in out of the cold"; "cold is a vasoconstrictor"

collision ; hit
(physics) a brief event in which two or more bodies come together; "the collision of the particles resulted in an exchange of energy and a change of direction"

coma ; comatoseness
a state of deep and often prolonged unconsciousness; usually the result of disease or injury

(astronomy) a relatively small extraterrestrial body consisting of a frozen mass that travels around the sun in a highly elliptical orbit

conjunction ; alignment
(astronomy) apparent meeting or passing of two or more celestial bodies in the same degree of the zodiac

a number representing a quantity assumed to have a fixed value in a specified mathematical context; "the velocity of light is a constant"

a configuration of stars as seen from the earth

coordinate ; co-ordinate
a number that identifies a position relative to an axis

an electrical discharge accompanied by ionization of surrounding atmosphere

of or from or pertaining to or characteristic of the cosmos or universe; "cosmic laws"; "cosmic catastrophe"; "cosmic rays"

cosmic dust
clouds of particles or gases occurring throughout interstellar space

cosmic ray
highly penetrating ionizing radiation of extraterrestrial origin; consisting chiefly of protons and alpha particles; collision with atmospheric particles results in rays and particles of many kinds

the metaphysical study of the origin and nature of the universe

cosmology ; cosmogony ; cosmogeny
the branch of astrophysics that studies the origin and evolution and structure of the universe

Crab Nebula
a remnant of a supernova detected first in 1054 AD

a bowl-shaped depression formed by the impact of a meteorite or bomb

the men and women who man a vehicle (ship, aircraft, etc.)

curve ; curvature
the property possessed by the curving of a line or surface

curve ; curved shape
the trace of a point whose direction of motion changes

dark matter
(cosmology) a hypothetical form of matter that is believed to make up 90 percent of the universe; it is invisible (does not absorb or emit light) and does not collide with atomic particles but exerts gravitational force

dawn ; dawning ; aurora ; daybreak ; break of day ; sunrise ; sunup
the first light of day; "we got up before dawn"; "they talked until morning"

time for Earth to make a complete rotation on its axis; "two days later they left"; "they put on two performances every day"; "there are 30,000 passengers per day"

(astronomy) the angular distance of a celestial body north or to the south of the celestial equator; expressed in degrees; used with right ascension to specify positions on the celestial sphere

degree ; arcdegree
a measure for arcs and angles; "there are 360 degrees in a circle"

density ; denseness
the amount per unit size

departure ; leaving
the act of departing

deuterium ; heavy hydrogen
an isotope of hydrogen which has one neutron (as opposed to zero neutrons in hydrogen)

discovery ; find
the act of discovering something

the property created by the space between two objects or points

separated in space or coming from or going to a distance; "distant villages"; "the sound of distant traffic"; "a distant sound"; "a distant telephone call"

distant ; remote
located far away spatially; "distant lands"; "remote stars"

an optical phenomenon resulting from the failure of a lens or mirror to produce a good image

the 3rd planet from the sun; the planet we live on; "the Earth moves around the sun"; "he sailed around the world"

eclipse ; occultation
one celestial body obscures another

the great circle representing the apparent annual path of the sun; the plane of the Earth's orbit around the sun; makes an angle of about 23 degrees with the equator; "all of the planets rotate the sun in approximately the same ecliptic"

ellipse ; oval
a closed plane curve resulting from the intersection of a circular cone and a plane cutting completely through it; "the sums of the distances from the foci to any point on an ellipse is constant"

empyrean ; firmament ; heavens ; welkin
the apparent surface of the imaginary sphere on which celestial bodies appear to be projected

entrance ; entry
the act of entering; "she made a grand entrance"

an imaginary line around the Earth forming the great circle that is equidistant from the north and south poles; "the equator is the boundary between the northern and southern hemispheres"

either of two times of the year when the sun crosses the plane of the earth's equator and day and night are of equal length

exobiology ; space biology ; astrobiology
the branch of biology concerned with the effects of outer space on living organisms and the search for extraterrestrial life

the outermost atmospheric layer

explode ; burst
burst outward, usually with noise; "The champagne bottle exploded"

a careful systematic search

explosion ; burst
the act of exploding or bursting; "the explosion of the firecrackers awoke the children"; "the burst of an atom bomb creates enormous radiation aloft"

explosion ; detonation
a violent release of energy caused by a chemical or nuclear reaction

extraterrestrial ; alien
a form of life assumed to exist outside the Earth or its atmosphere

flight ; flying
an instance of traveling by air; "flying was still an exciting adventure for him"

fossil fuel
fuel consisting of the remains of organisms preserved in rocks in the earth's crust with high carbon and hydrogen content

full moon
the time when the Moon is fully illuminated; "the moon is at the full"

Gagarin ; Yuri Gagarin ; Yuri Alekseyevich Gagarin
Soviet cosmonaut who in 1961 was the first person to travel in space (1934-1968)

galaxy ; extragalactic nebula
(astronomy) a collection of star systems; any of the billions of systems each having many stars and nebulae and dust; "`extragalactic nebula' is a former name for `galaxy'"

existing as or having characteristics of a gas; "steam is water is the gaseous state"

a zodiacal constellation in the northern hemisphere between Taurus and Cancer on the ecliptic

giant star ; giant
a very bright star of large diameter and low density (relative to the Sun)

gravity ; gravitation
(physics) the force of attraction between all masses in the universe; especially the attraction of the earth's mass for bodies near its surface; "the more remote the body the less the gravity"; "the gravitation between two bodies is proportional to the product of their masses and inversely proportional to the square of the distance between them"; "gravitation cannot be held responsible for people falling in love"--Albert Einstein

greenhouse effect ; greenhouse warming
warming that results when solar radiation is trapped by the atmosphere; caused by atmospheric gases that allow sunshine to pass through but absorb heat that is radiated back from the warmed surface of the earth

Greenwich Mean Time ; Greenwich Time ; GMT
the local time at the 0 meridian passing through Greenwich, England; it is the same everywhere

a circle of light around the sun or moon

heat ; high temperature
the presence of heat

the region inside the heliopause containing the sun and solar system

half of a sphere

Herschel ; William Herschel ; Sir William Herschel
English astronomer (born in Germany) who discovered infrared light and who catalogued the stars and discovered the planet Uranus (1738-1822)

horizon ; skyline
the line at which the sky and Earth appear to meet

a period of time equal to 1/24th of a day; "the job will take more than an hour"

hydrogen ; H
a nonmetallic univalent element that is normally a colorless and odorless highly flammable diatomic gas; the simplest and lightest and most abundant element in the universe

a tentative insight into the natural world; a concept that is not yet verified but that if true would explain certain facts or phenomena; "a scientific hypothesis that survives experimental testing becomes a scientific theory"; "he proposed a fresh theory of alkalis that later was accepted in chemical practices"

ice age
any period of time during which glaciers covered a large part of the earth's surface; "the most recent ice age was during the Pleistocene"

inclination ; inclination of an orbit
(astronomy) the angle between the plane of the orbit and the plane of the ecliptic stated in degrees

interstellar medium
interstellar space including streams of protons moving from the stars

the outer region of the Earth's atmosphere; contains a high concentration of free electrons

isotropy ; symmetry
(physics) the property of being isotropic; having the same value when measured in different directions

jet stream
a high-speed high-altitude airstream blowing from west to east near the top of the troposphere; has important effects of the formation of weather fronts

journey ; journeying
the act of traveling from one place to another

Jovian planet ; gas giant
any of the four outermost planets in the solar system; much larger than Earth and gaseous in nature (like Jupiter)

the largest planet and the 5th from the sun; has many satellites and is one of the brightest objects in the night sky

the angular distance between an imaginary line around a heavenly body parallel to its equator and the equator itself

launch for the first time; launch on a maiden voyage; "launch a ship"

leap year ; bissextile year
in the Gregorian calendar: any year divisible by 4 except centenary years divisible by 400

(astronomy) a real or apparent slow oscillation of a moon or satellite; "the libration of the moon"

lightness ; weightlessness
the property of being comparatively small in weight; "the lightness of balsa wood"

luminosity ; luminance
the quality of being luminous; emitting or reflecting light; "its luminosity is measured relative to that of our sun"

lunar eclipse
the earth interrupts light shining on the moon

magnetic declination ; magnetic variation ; variation
the angle (at a particular location) between magnetic north and true north

the magnetic field of a planet; the volume around the planet in which charged particles are subject more to the planet's magnetic field than to the solar magnetic field

the act of expanding something in apparent size

the property of relative size or extent (whether large or small); "they tried to predict the magnitude of the explosion"; "about the magnitude of a small pea"

a diagrammatic representation of the earth's surface (or part of it)

Mars ; Red Planet
a small reddish planet that is the 4th from the sun and is periodically visible to the naked eye; minerals rich in iron cover its surface and are responsible for its characteristic color; "Mars has two satellites"

the property of a body that causes it to have weight in a gravitational field

the smallest planet and the nearest to the sun

meridian ; line of longitude
an imaginary great circle on the surface of the earth passing through the north and south poles at right angles to the equator; "all points on the same meridian have the same longitude"

the atmospheric layer between the stratosphere and the thermosphere

meteor ; shooting star
a streak of light in the sky at night that results when a meteoroid hits the earth's atmosphere and air friction causes the meteoroid to melt or vaporize or explode

meteor shower ; meteor stream
a transient shower of meteors when a meteor swarm enters the earth's atmosphere

stony or metallic object that is the remains of a meteoroid that has reached the earth's surface

meteoroid ; meteor
(astronomy) any of the small solid extraterrestrial bodies that hits the earth's atmosphere

a colorless odorless gas used as a fuel

minute ; min
a unit of time equal to 60 seconds or 1/60th of an hour; "he ran a 4 minute mile"

month ; calendar month
one of the twelve divisions of the calendar year; "he paid the bill last month"

Moon ; moon
the natural satellite of the Earth; "the average distance to the Moon is 384,400 kilometers"; "men first stepped on the moon in 1969"

the point below the observer that is directly opposite the zenith on the imaginary sphere against which celestial bodies appear to be projected

the guidance of ships or airplanes from place to place

an immense cloud of gas (mainly hydrogen) and dust in interstellar space

a giant planet with a ring of ice particles; the 8th planet from the sun is the most remote of the gas giants; "the existence of Neptune was predicted from perturbations in the orbit of Uranus and it was then identified in 1846"

neutron star
a star that has collapsed under its own gravity; it is composed of neutrons

new moon ; new phase of the moon
the time at which the Moon appears as a narrow waxing crescent

a star that ejects some of its material in the form of a cloud and become more luminous in the process

(astronomy) the cosmic synthesis of atoms more complex than the hydrogen atom

uncontrolled nodding

a large body of water constituting a principal part of the hydrosphere

Oort cloud
(astronomy) a hypothetical huge collection of comets orbiting the sun far beyond the orbit of Pluto; perturbations (as by other stars) can upset a comet's orbit and may send it tumbling toward the sun

orbit ; celestial orbit
the (usually elliptical) path described by one celestial body in its revolution about another; "he plotted the orbit of the moon"

order of magnitude ; magnitude
a number assigned to the ratio of two quantities; two quantities are of the same order of magnitude if one is less than 10 times as large as the other; the number of magnitudes that the quantities differ is specified to within a power of 10

outburst ; burst
a sudden intense happening; "an outburst of heavy rain"; "a burst of lightning"

outer space ; space
any location outside the Earth's atmosphere; "the astronauts walked in outer space without a tether"; "the first major milestone in space exploration was in 1957, when the USSR's Sputnik 1 orbited the Earth"

a colorless gas (O3) soluble in alkalis and cold water; a strong oxidizing agent; can be produced by electric discharge in oxygen or by the action of ultraviolet radiation on oxygen in the stratosphere (where it acts as a screen for ultraviolet radiation)

ozone layer ; ozonosphere
a layer in the stratosphere (at approximately 20 miles) that contains a concentration of ozone sufficient to block most ultraviolet radiation from the sun

the apparent displacement of an object as seen from two different points that are not on a line with the object

an imaginary line around the Earth parallel to the equator

parsec ; secpar
a unit of astronomical length based on the distance from Earth at which stellar parallax is 1 second of arc; equivalent to 3.262 light years

a fringe region of partial shadow around an umbra

any state or process known through the senses rather than by intuition or reasoning

the intensely luminous surface of a star (especially the sun)

any celestial body (other than comets or satellites) that revolves around a star

a building housing an instrument for projecting the positions of the planets onto a domed ceiling

planetary ; terrestrial
of or relating to or characteristic of the planet Earth or its inhabitants; "planetary rumblings and eructations"- L.C.Eiseley ; "the planetary tilt"; "this terrestrial ball"

planetary nebula
a nebula that was once thought to be a star with its planets but is now thought to be a very hot star surrounded by an expanding envelope of ionized gases that emit a fluorescent glow because of intense radiation from the star

(physical chemistry) a fourth state of matter distinct from solid or liquid or gas and present in stars and fusion reactors; a gas becomes a plasma when it is heated until the atoms lose all their electrons, leaving a highly electrified collection of nuclei and free electrons; "particles in space exist in the form of a plasma"

a small planet and the farthest known planet from the sun; it has the most elliptical orbit of all the planets; "Pluto was discovered by Clyde Tombaugh in 1930"

pole ; celestial pole
one of two points of intersection of the Earth's axis and the celestial sphere

pole star ; polestar
the brightest star in Ursa Minor; at the end of the handle of the Little Dipper; the northern axis of the earth points toward it

prime meridian
meridian at zero degree longitude from which east and west are reckoned (usually the Greenwich longitude in England)

a flexible slender surgical instrument with a blunt end that is used to explore wounds or body cavities

propellant ; propellent
any substance that propels

propulsion ; actuation
the act of propelling

a stable particle with positive charge equal to the negative charge of an electron

a degenerate neutron star; small and extremely dense; rotates very fast and emits regular pulses of polarized radiation

having four sides and four angles

quasar ; quasi-stellar radio source
a starlike object that may send out radio waves and other forms of energy; many have large red shifts

the act of spreading outward from a central source

radio astronomy
the branch of astronomy that detects and studies the radio waves emitted by celestial bodies

(medicine) the treatment of disease (especially cancer) by exposure to a radioactive substance

radius ; r
the length of a line segment between the center and circumference of a circle or sphere

range ; scope
an area in which something acts or operates or has power or control: "the range of a supersonic jet"; "a piano has a greater range than the human voice"; "the ambit of municipal legislation"; "within the compass of this article"; "within the scope of an investigation"; "outside the reach of the law"; "in the political orbit of a world power"

red dwarf ; red dwarf star
a small, old, relatively cool star; approximately 100 times the mass of Jupiter

red shift ; redshift
(astronomy) a shift in the spectra of very distant galaxies toward longer wavelengths (toward the red end of the spectrum); generally interpreted as evidence that the universe is expanding

reflecting telescope ; reflector
optical telescope consisting of a large concave mirror that produces an image that is magnified by the eyepiece; "Isaac Newton invented the reflecting telescope in 1668"

refracting telescope
optical telescope that has a large convex lens that produces an image that is viewed through the eyepiece

Reich ; Wilhelm Reich
Austrian born psychoanalyst who lived in the United States; advocated sexual freedom and believed that cosmic energy could be concentrated in a human being (1897-1957)

resistance ; opposition
the action of opposing something that you disapprove or disagree with; "he encountered a general feeling of resistance from many citizens"; "despite opposition from the newspapers he went ahead"

right ascension ; RA ; celestial longitude
(astronomy) the equatorial coordinate specifying the angle, measured eastward along the celestial equator, from the vernal equinox to the intersection of the hour circle that passes through an object in the sky; usually expressed in hours and minutes and seconds; used with declination to specify positions on the celestial sphere; "one hour of right ascension equals fifteen degrees"

rocket ; projectile
any vehicle self-propelled by a rocket engine

rocket ; rocket engine
a jet engine containing its own propellant and driven by reaction propulsion

rotation ; rotary motion
the act of rotating as if on an axis; "the rotation of the dancer kept time with the music"

satellite ; orbiter
man-made equipment that orbits around the earth or the moon

a giant planet that is surrounded by three planar concentric rings of ice particles; the 6th planet from the sun

of or relating to the practice of science; "scientific journals"

a person with advanced knowledge of one or more sciences

a period of the year marked by special events or activities in some field; "he celebrated his 10th season with the ballet company"; "she always looked forward to the avocado season"

second ; sec
1/60 of a minute; the basic unit of time adopted under the Systeme International d'Unites

a measuring instrument for measuring the angular distance between celestial objects; resembles an octant

transport commercially

bobbin that passes the weft thread between the warp threads

sidereal day ; day
the time for one complete rotation of the earth relative to a particular star, about 4 minutes shorter than a mean solar day

sidereal time
measured by the diurnal motion of stars

sidereal year
the time for the earth to make one complete revolution around the sun, relative to the fixed stars

the atmosphere and outer space as viewed from the earth

United States space station; in orbit from 1973 to 1979

relating to or derived from the sun or utilizing the energies of the sun; "solar eclipse"; "solar energy"

solar eclipse
the moon interrupts light from the sun

solar energy ; solar power
energy from the sun that is converted into thermal or electrical energy; "the amount of energy falling on the earth is given by the solar constant, but very little use has been made of solar energy"

solar system
the sun with the celestial bodies that revolve around it in its gravitational field

solar wind
a stream of protons moving radially from the sun

either of the two times of the year when the sun is at its greatest distance from the celestial equator

situated in or facing or moving toward or coming from the south; "the south entrance"

space ; infinite
the unlimited expanse in which everything is located; "they tested his ability to locate objects in space"; "the boundless regions of the infinite"

space probe
a rocket-propelled guided missile that can escape the earth's atmosphere; makes observations of the solar system that cannot be made by terrestrial observation

space shuttle
a reusable spacecraft with wings for a controlled descent through the Earth's atmosphere

spaceflight ; space travel ; spacefaring
a voyage outside the Earth's atmosphere

a pressure suit worn by astronauts while in outer space

spectroscopy ; spectrometry
the use of spectroscopes to analyze spectra

an ordered array of the components of an emission or wave

speed ; velocity
distance travelled per unit time

speed of light
the speed at which light travels in a vacuum; the constancy and universality of the speed of light is recognized by defining it to be exactly 299,792,458 meters per second

a three-dimensional closed surface such that every point on the surface is equidistant from the center

of or relating to spheres or resembling a sphere; "spherical geometry"

spheroid ; ellipsoid of revolution
a shape that is generated by rotating an ellipse around one of its axes; "it looked like a sphere but on closer examination I saw it was really a spheroid"

spiral galaxy ; spiral nebula
a galaxy having a spiral structure; arms containing younger stars spiral out from old stars at the center

spring ; springtime
the season of growth; "the emerging buds were a sure sign of spring"; "he will hold office until the spring of next year"

(astronomy) a celestial body of hot gases that radiates energy derived from thermonuclear reactions in the interior

starship ; spaceship
a spacecraft designed to carry a crew into interstellar space (especially in science fiction)

the atmospheric layer between the troposphere and the mesosphere

summer ; summertime
the warmest season of the year; in the northern hemisphere it extends from the summer solstice to the autumnal equinox; "they spent a lazy summer at the shore"

sun ; Sun
the star that is the source of light and heat for the planets in the solar system; "the sun contains 99.85% of the mass in the solar system"; "the Earth revolves around the Sun"

sunlight ; sunshine
the rays of the sun; "the shingles were weathered by the sun and wind"

atmospheric phenomena accompanying the daily appearance of the sun

sunset ; sundown
the time in the evening at which the sun begins to fall below the horizon

sunspot ; macula
a cooler darker spot appearing periodically on the sun's photosphere; associated with a strong magnetic field

an extremely bright star of very large diameter and low density

a star that explodes and becomes extremely luminous in the process

a zodiacal constellation in the northern hemisphere near Orion; between Aries and Gemini

telescope ; scope
a magnifier of images of distant objects

the degree of hotness or coldness of a body or environment (corresponding to its molecular activity)

tendency ; inclination
a characteristic likelihood of or natural disposition toward a certain condition or character or effect; "the alkaline inclination of the local waters"; "fabric with a tendency to shrink"

Tereshkova ; Valentina Tereshkova ; Valentina Vladmirovna Tereshkova
Soviet cosmonaut who was the first woman in space (born in 1937)

terrestrial planet
a planet having a compact rocky surface like the Earth's; the four innermost planets in the solar system

theodolite ; transit
a surveying instrument for measuring horizontal and vertical angles, consisting of a small telescope mounted on a tripod

the atmospheric layer between the mesosphere and the exosphere

the periodic rise and fall of the sea level under the gravitational pull of the moon

time ; fourth dimension
the fourth coordinate that is required (along with three spatial dimensions) to specify a physical event

time zone
any of the 24 regions of the globe (loosely divided by longitude) throughout which the same standard time is used

Tombaugh ; Clyde Tombaugh ; Clyde William Tombaugh
United States astronomer who discovered the planet Pluto (1906-1997)

trajectory ; flight
the path followed by an object moving through space

either of two parallels of latitude about 23.5 degrees to the north and south of the equator representing the points farthest north and south at which the sun can shine directly overhead and constituting the boundaries of the Torrid Zone or tropics

the lowest atmospheric layer; from 4 to 11 miles high (depending on latitude)

twilight ; dusk ; gloaming ; nightfall
the time of day immediately following sunset; "he loved the twilight"; "they finished before the fall of night"

universe ; cosmos
everything that exists anywhere; "they study the evolution of the universe"; "the biggest tree in existence"

a giant planet with a ring of ice particles; the 7th planet from the sun has a blue-green color and many satellites; "Uranus was discovered by William Herschel in 1781"

a symbol (like x or y) that is used in mathematical or logical expressions to represent a variable quantity

a conveyance that transports people or objects

the second nearest planet to the sun; it is peculiar in that its rotation is slow and retrograde (in the opposite sense of the Earth and all other planets except Uranus); it is visible from Earth as an early `morning star' or an `evening star'; "before it was known that they were the same object the evening star was called Venus and the morning star was called Lucifer"

optical device that helps a user to find the target of interest

a large zodiacal constellation on the equator; between Leo and Libra

volcano ; vent
a fissure in the earth's crust (or in the surface of some other planet) through which molten lava and gases erupt

the distance (measured in the direction of propagation) between two points in the same phase in consecutive cycles of a wave

the atmospheric conditions that comprise the state of the atmosphere in terms of temperature and wind and clouds and precipitation; "they were hoping for good weather"; "every day we have weather conditions and yesterday was no exception"; "the conditions were too rainy for playing in the snow"

week ; calendar week
a period of seven consecutive days starting on Sunday

the vertical force exerted by a mass as a result of gravity

weight unit ; weight
a unit used to measure weight; "he placed two weights in the scale pan"

white dwarf ; white dwarf star
a faint star of enormous density

Wilson ; Robert Woodrow Wilson
United States physicist honored for his work on cosmic microwave radiation (born in 1918)

winter ; wintertime
the coldest season of the year; in the northern hemisphere it extends from the winter solstice to the vernal equinox

winter solstice
December 22, when the sun is at its southernmost point

hole made by a burrowing worm

year ; twelvemonth
a period of time containing 365 (or 366) days; "she is 4 years old"; "in the year 1920"

the point above the observer that is directly opposite the nadir on the imaginary sphere against which celestial bodies appear to be projected

(astrology) a circular diagram representing the 12 zodiacal constellations and showing their signs

zodiacal light
a luminous tract in the sky; a reflection of sunlight from cosmic dust in the plane of the ecliptic; visible just before sunrise and just after sunset

a locally circumscribed place characterized by some distinctive features

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