| N | O | P | Q | R | S | T | U | V | X | Y | Z |
| absolute zero | The lowest possible temperature in theory: 0 Kelvin, or -459.6 deg Fahrenheit (-273.15 deg Celsius). |
|---|---|
| achromatic lens | A lens made up from two different types of glass, which reduces chromatic aberration. |
| aerodynamic brake | A device for slowing down a space vehicle; it works by creating resistance to an atmosphere. |
| air telescope | An early, very long type of refracting telescope which had no tube between the eyepiece and the objective lens. |
| albedo | The reflectiveness of a body, expressed as a percentage of sunlight reaching it. |
| algae | Primitive water-dwelling plants with simple structures. Searches by space probes look for clues of primitive forms of life. |
| antenna | The receiving component of a radio telescope or receiver, and the transmitting component of a transmitter. |
| aperature | The diameter of the objective lens or primary mirror of a telescope |
| aphelion | the point in a planet's orbit when it is farthest form the Sun. |
| apochromatic lens | A lens made up from three different types of glass, which reduces chromatic aberration. |
| asteroid | One of thousands of minor planets in our solar system, mainly less than 60 miles (100 kilometers) in diameter, & most of which lie between Mars and Jupiter. |
| asteroid belt | The region between the orbits of Mars and Jupiter where most asteroids orbit the Sun. |
| asthenosphere | The hot, mobile region of the Earth's mantle, beneath the tectonic plates. |
| astrology | The forerunner of astronomy, in which predictions were made about events and human personalities by referring to the position of the Sun, Moon and planets, particularly at the time of a person's birth. |
| astronomical unit | (AU) A unit of measurement equal to the Earth's distance from the Sun, about 93,000,000 miles (150,000,000 kilometers). |
| atmosphere | The envelope of gases that surround and protect planets and other heavenly bodies, including Earth. |
| atmospheric pressure | The weight of a body's atmosphere at a given altitude, expressed as weight per unit area. |
| atom | The smallest stable component of a chemical element. |
| bar | One unit of Earth's atmospheric pressure at sea-level, about 15 pounds per square inch. |
| black hole | An invisibile region in space surrounding a collapsed star, from which no light can escape. |
| bow-shock | The region where a planet's magnetosphere meets the solar wind. |
| caldera | The shallow basin on the site of a volcanic explosion. |
| canali | Canal-like markings observed on the surface of Mars and once thought to be irrigation channels. |
| carbonaceous | Containing organic compounds. |
| carboniferous period | The period on Earth between 280,000,000 and 250,000,000 years ago when forests laid down the coal beds we use today. Other terrestrial planets may have similar a history. |
| Cassini Division | A 2,500-mile (4,000-kilometer) wide gape between Saturn's A and B rings, discovered in 1675 by Giovanni Domenico Cassini. |
| Celsius scale | A temperature scale with freezing point at 0º and boiling point at 100º (of water). |
| centrifugal force | The force exerted outward from the radius of a spinning body. |
| chromatic abberation | False colors caused by the difficulty of bringing all colors to a single focus when viewing an image. |
| Comet | A body or piece of space debris, made up of ice, gas, and dust, that orbits the Sun, usually with a very eccentric orbit. A long bright tail, visible from Earth, forms when the comet is close to the Sun. |
| constellation | One of the 88 named regions that make up the night sky and its stars as seen from Earth. |
| convection current | A cyclical movement in liquids and gases caused by heating and cooling processes. |
| co-orbital | Two or more satellites following the same orbit around their parent body are said to be co-orbital. |
| crust | The Earth's surface layer, about 20 miles (32 kilometers) thick in continental regions, and some 6 miles (10 kilometers) thick beneath the oceans. |
| current sheet | A flattened disk of charged particles rotating approximately in the plane of Jupiter's magnetic equator. |
| decametric radiation | Radio emissions from Jupiter which occur in irregular bursts at wavelengths of more than 25 feet (7.5 meters). |
| descent module | Part of a space probe, designed to descend separate from the main craft to or toward a body's surface. |
| deuterium | One of the three isotopes of hydrogen, having a nucleus of a proton and a neutron. |
| differentiation | A process early in a planet's formation by which the dense elements, often metallic, sink to form a core, while lighter material forms the outer layers |
| doppler effect | The apparent change in a sound or color as it approaches or recedes from Earth. |
| DNA | Deoxyribonucleic acid, a component of living cells that contains heredity information. This is a specific item that space scientists search for when probing the planets. |
| dry ice | Frozen carbon dioxide. |
| eccentric orbit | An orbit that is not circular. |
| eclipse | The total or partial blotting out of the light from a body in space by the shadow of another body; when the body of the Moon blots out the Sun, we also call that an eclipse, though the correct term is "occultation." |
| ecliptic | The circle where the plane of Earth's orbit meets the celestial sphere. |
| ejecta | Material thrown up and out during a crater-forming meterotie impact. |
| equator | The surface circle that divides a planet into equal northern and southern hemispheres. |
| equatorial jet | A powerful wind racing round a planet's equatorial region, usually at high altitude. |
| equatorial plane | The theoretical or imaginary plane extending through the equator of a planet. |
| escape velocity | The minimum speed necessary for any object to escape a particular gravitational field. |
| fly-by | The passage of a spacecraft close to a planet or moon for observation and analysis; an observational flight by a spacecraft that passes close to a planet or satellite. |
| focal length | The distance between the lens or primary mirror and the point of focus of a telescope. |
| fossil fuel | Fuel including petroleum, natural gas and coal, found in ancient organic deposits. |
| G | A unit of measurement equal to one Earth gravity, for measuring the pressure of acceleration. |
| galaxy | A cluster or vast system of stars, planets, gas, and dust held together by the interaction of gravitational forces. Our solar system lies in the Milky Way Galaxy, which contains some 200 billion stars. |
| Galilean moons | The four largest moons of Jupiter, discovered by Galileo Galilei, in the 1600s: Ganymede, Callisto, Io and Europa. |
| gas giant | One of the outer planets, Jupiter, Saturn, Uranus and Neptune, which are composed principally of gases. |
| gravity | The force of attraction that material bodies in space exert on one another. |
| gravity deflection | The technique of "skipping" a spacecraft off a planet's gravitational field to speed it on its way. |
| greenhouse effect | Increased temperature on a planet due to a build-up of carbon dioxide in the upper atmosphere. |
| hemisphere | Half of a sphere, such as a planet or moon. |
| ice age | A period of long-term recurring cold climate, with a widespread ice cover. |
| ice cap | Ice cover at the poles of a planet which sometimes advance and recede seasonally. |
| image photopolarimeter | A scanning telescope fitted with instruments to analyse the polarization of light and linked to TV-type cameras. |
| inclined orbit | A planetary or other orbit going around the Sun at an angle to the plane of the ecliptic. |
| inferior planaet | A planet with an orbit closer to the Sun than the Earth's orbit. |
| infrared camera | A camera whcih records images from infrared emanations, between the radio and visible bands of electromagnetic spectrum. |
| interstellar space | The region of near-vacuum existing between the stars of our galaxy. |
| ionosphere | An atmostpheric layer containing free electrons and ions; the ionosphere of Venus extends to about 250 miles (400 Kilometers) above the planet's surface. |
| latitude | The distance north or south of the equator of a planet, measured in degrees. |
| launch window | The period when the orbits of various planets are most conveniently aligned for a space launch. |
| lava field | A characteristic volcanic terrain created by the flow of molten material. |
| light-year | the distance traveled by a ray of light in one year in a vacuum: 63,240 Astronomical Units (AU). |
| long axis | The longest center line dissecting an irregular or elongated body or shape. |
| longitude | The distance on the surface of a planet east or west of a given meridian line. |
| magnetic axis | The imaginary line through the magnetic poles of a planet or satellite. |
| magnetic flux tube | A loop of magnetic field lines connecting the moon Io to Jupiter, which cause bursts of radi noise. |
| magnetopause | The outer boundary of a planet's manetoshpere outside which is the magnetosheath. |
| magnetosheath | The region of turbulence between a planet's magnetoshpere and its bow-shock. |
| magnetosphere | The envelope aroudn a planet in which its magnetic field has significant effect. |
| magnetotail | The tail of a planet's magnetoshpere, carried "downstream" by the solar wind. |
| magnification | Measurement of the strength of a lens. |
| mantle | The thick layer of rock ling between the Earth's molten core and the surface. |
| mass | The total quantity of material in a body. |
| mean distance | The average distance of, for example, a planet following a non-circular orbit of the Sun. |
| metallic hydrogen | A form of liquid hydrogen that exists under conditions of great pressure and heat, and which is found only in the gas giant planets and in the Sun and stars. |
| meteroid | A piece of rock or metal, usually very small, hurtling through space. Meteroids that enter Earth's atmosphere and burn up are called meteors, also known as "shooting stars." Those that reach the ground are meteorites. |
| meteorite | A fragment of interplanetary material that reaches the surface of a planet or satellite after being snared by its gravitational field. |
| microbe | A minute living organism; it can be an animal or a plant. |
| microbiology | The study of microscopic forms of life. |
| micrometeorite | A particle of cosmic dust which is so msall that it slows down when it enters an atmosphere and free-fails to the surface without heating up. |
| molecule | A combination of two or more atoms bound together. |
| nuclear generator | Electrical generator on space probes going to Jupiter and beyond, which converts heat from the radioactive decay of certain elements into electrical power. |
| nutrient | A substance which provides nourishment for living organisms. |
| objective lens | The lens in a refracting telescope that is closest to the observed object. |
| oblateness | The flattening of a spherical body because of its rotation; it is measured by subtracting the polar diameter from the equatorial diameter and dividing the result by the equatorial diameter. |
| observatory | A structure, usually equipped with telescopes, designed and built for the study of astronomy. |
| opposition | The position of a planet when it is directly opposite the Sun as seen from Earth, that is, with Earth between the planet and the Sun. |
| orbit | The path of a body in space as it moves around another, within the influence of its gravitational field. |
| orbital period | The time taken by a planet, asteroid or comet to complete one orbit. |
| optical telescope | A telescope with lenses and/or mirror that depends on light-gathering, as opposed to a radio- or infrared telescope. |
| orbitor | Part of a spacecraft designed to orbit the body being investigated. |
| ozone | A form of oxygen with three molecules (O3); a layer of ozone protects Earth from excess ultraviolet radiation. |
| paralax | An apparent shift in an object's position caused by moving the point from which it is observed. |
| parsec | A unit of distance, usually extending beyond the Solar System: 3.26 light years. |
| perihelion | The point in a planet's orbit when it is closets to the Sun. |
| permafrost | Permanently frozen ground beneath a planet's surface. |
| photochemical smog | Fog caused by the effects of sunlight on hydrocarbon emissions. |
| pixel | A small computer image used to build pictures on visual display screens. |
| planet | A large non-glowing body that moves in orbit around a star and shines only by reflected light form the star. |
| planetesimal | Intermediate objects between grains of matter and the planets; the building blocks of the planets. |
| precession | The slow movement of the Earth's axis, which describes a circle every 26,000 years due to the gravitational pulls of the Sun and the Moon. |
| prime meridian | The circular line of zero longitude on a mapped body, from which other lines of longitude are measured. |
| primordial soup | The warm, shallow waters, laced with carbon compounds, in which life may have originated on Earth. |
| prism | A translucent device with intersecting plane surfaces that can separate "white" light into its color spectrum. |
| rad | A unit for measuring the dose of radiation absorbed by any material. |
| radial velocity | The speed at which a body in space approaches or recedes from Earth. |
| radio frequency map | The image of a region or body created from recordings of its radio emissions. |
| radioactive decay | The disintegration of certain atomic nuclei, with the emission of sub-atomic particles and gamma rays. |
| red shift | The apparent reddening of the light emitted by another galaxy, showing it is receding. |
| refracting telescope | A telescope in which lenses are the main optical component. |
| relative density | The density of a body relative to the density of water. |
| retrograde orbit | A closkwise orbital motion, as seen from the north pole of a planet; most Solar System orbits are counterclockwise. Examples of planets are Venus and Uranus; example of satellite are Jupiter's outer moons, Ananke, Carme, Pasiphae and Sinope, and Saturn's moon Phoebe. |
| rift valley | A wide, steep-sided valley caused by subsidence along faults. |
| roche limit | The minimum distance at which a satellite can maintain a stable orbit without being destroyed by tidal forces; determined to be 60º by J.L. Lagrange. |
| satellite | An object that orbits a planet or other body. The Moon, for example, is a satellite of Earth, while the Earth is a satellite of the Sun. |
| shield volcano | A volcano with a wide base, whcih has gently sloping sides formed by extensive lava flows. |
| solar panel | An array of photovoltaic cells that can produce electricity from sunlight. |
| Solar System | The collective term for the Sun, the nine planets, and all of the satellites, comets, asteroids, meteroids, dust, and gas that orbit the Sun. |
| solar wind | A flow of charged atomic particles from the Sun radiating throughout the Solar System. |
| space shuttle | A recoverable, delta-winged space carrier and orbitor operated by NASA. |
| spectral line | A visible line in a spectrum indivcating the presence of a particular substance. |
| spectrometer | An instrument for recording the intensity of a radiation source, often carried on space probes. |
| splosh crater | An impact crater in frozen ground that has melted and splashed outward, to resemble a mud splash. |
| star | A glowing, self-illuminating sphere or body of gas in space; the Sun is the nearest star to Earth. |
| supernova | A late stage in the life of some stars, when they explode with a huge release of energy. |
| synchronous rotation | The movement of a satellite around its parent planet, in which the satellite rotates once on its own axis for every orbit it makes. |
| tectonic plate | A section of a celestial body's crust moved by geological forces. |
| thermal imager | An instrument for recording patterns of heat variation as a visual image. |
| thermal radiation | Electromagnetic radiation emitted from a heat source. |
| tidal drag | A force, arising from a complex gravitational system, which can physically distort one or more of the bodies involved. |
| torus | A "ring doughnut" shape, like the plasma, torus around Jupiter following Io's orbit comprising debris thrown out by Io's volcanoes. |
| trace element | A substance found in such small quantities that it is measured in terms of a few parts per million. |
| vesicular rock | Rock associated with volcanic activity and pitted with large numbers of small gas escape holes. |
| zodiac | A band around the celestial sphere which is divided by ancient astronomers into 12 parts, or signs, representing constellations. |
| ~ | ~ Return to the Solar System ~ | ~ Planetary Statistics ~ | ~ | ||
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Refiner of Gold Creations |
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1998 Solar System Facts Created by EMC on 6/23/1997. Updated 5/4/2005.
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