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magnetic sail | Space and Astronomy | 1 | or magsail , is a proposed method of spacecraft propulsion which would use a static magnetic field to deflect charged particles radiated by the Sun as a plasma wind, and thus impart momentum to accelerate the spacecraft. A magnetic sail could also thrust directly against planetary and solar magnetospheres . |
magnetoplasmadynamic thruster | Space and Astronomy | 1 | A magnetoplasmadynamic (MPD) thruster ( MPDT ) is a form of electrically powered spacecraft propulsion which uses the Lorentz force (the force on a charged particle by an electromagnetic field) to generate thrust. It is sometimes referred to as Lorentz Force Accelerator (LFA) or (mostly in Japan) MPD arcjet. |
mass | Space and Astronomy | 1 | The mass of a planet is the amount of matter in the planet, which is not always the same as its “size.” Exoplanet masses are measured in comparison to Earth for smaller rocky planets, or Jupiter for big gas planets. The standard unit of mass is the kilogram (kg), and the Earth’s mass is about 5.97 x 1024 kg. |
mass driver | Space and Astronomy | 1 | or electromagnetic catapult , is a proposed method of non-rocket spacelaunch which would use a linear motor to accelerate and catapult payloads up to high speeds. All existing and contemplated mass drivers use coils of wire energized by electricity to make electromagnets . Sequential firing of a row of electromagnets accelerates the payload along a path. After leaving the path, the payload continues to move due to momentum . |
moment of inertia | Space and Astronomy | 1 | otherwise known as the mass moment of inertia , angular mass , second moment of mass , or most accurately, rotational inertia , of a rigid body is a quantity that determines the torque needed for a desired angular acceleration about a rotational axis, akin to how mass determines the force needed for a desired acceleration . It depends on the body's mass distribution and the axis chosen, with larger moments requiring more torque to change the body's rate of rotation. |
momentum | Space and Astronomy | 1 | In Newtonian mechanics , linear momentum , translational momentum , or simply momentum is the product of the mass and velocity of an object. It is a vector quantity, possessing a magnitude and a direction. If m is an object's mass and v is its velocity (also a vector quantity), then the object's momentum p is |
monopropellant rocket | Space and Astronomy | 1 | or monochemical rocket , is a rocket that uses a single chemical as its propellant . |
motion | Space and Astronomy | 1 | In physics , motion is the phenomenon in which an object changes its position . is mathematically described in terms of displacement , distance , velocity , acceleration , speed , and time . The motion of a body is observed by attaching a frame of reference to an observer and measuring the change in position of the body relative to that frame with change in time. The branch of physics describing the motion of objects without reference to its cause is kinematics ; the branch studying forces and their effect on motion is dynamics . |
multistage rocket | Space and Astronomy | 1 | or step rocket is a launch vehicle that uses two or more rocket stages , each of which contains its own engines and propellant . A tandem or serial stage is mounted on top of another stage; a parallel stage is attached alongside another stage. The result is effectively two or more rockets stacked on top of or attached next to each other. Two-stage rockets are quite common, but rockets with as many as five separate stages have been successfully launched. |
naca | Space and Astronomy | 1 | United States National Advisory Committee for Aeronautics, replaced by NASA in 1958. |
nasa | Space and Astronomy | 1 | National Aeronautics and Space Administration |
navier–stokes equations | Space and Astronomy | 1 | In physics , the ( / n æ v ˈ j eɪ s t oʊ k s / ) are certain partial differential equations which describe the motion of viscous fluid substances, named after French engineer and physicist Claude-Louis Navier and Anglo-Irish physicist and mathematician George Gabriel Stokes . They were developed over several decades of progressively building the theories, from 1822 (Navier) to 1842–1850 (Stokes). |
newton | Space and Astronomy | 1 | (unit) – The newton (symbol: N ) is the International System of Units (SI) derived unit of force . It is named after Isaac in recognition of his work on classical mechanics , specifically 's second law of motion . |
newton's law of universal gravitation | Space and Astronomy | 1 | is usually stated as that every particle attracts every other particle in the universe with a force that is directly proportional to the product of their masses and inversely proportional to the square of the distance between their centers. The publication of the theory has become known as the " first great unification ", as it marked the unification of the previously described phenomena of gravity on Earth with known astronomical behaviors. |
newton's laws of motion | Space and Astronomy | 1 | are three laws of classical mechanics that describe the relationship between the motion of an object and the forces acting on it. These laws can be paraphrased as follows: |
nose cone design | Space and Astronomy | 1 | Given the problem of the aerodynamic design of the nose cone section of any vehicle or body meant to travel through a compressible fluid medium (such as a rocket or aircraft , missile or bullet ), an important problem is the determination of the nose cone geometrical shape for optimum performance. For many applications, such a task requires the definition of a solid of revolution shape that experiences minimal resistance to rapid motion through such a fluid medium. |
nozzle | Space and Astronomy | 1 | is a device designed to control the direction or characteristics of a fluid flow (especially to increase velocity) as it exits (or enters) an enclosed chamber or pipe . A nozzle is often a pipe or tube of varying cross-sectional area, and it can be used to direct or modify the flow of a fluid ( liquid or gas ). s are frequently used to control the rate of flow, speed, direction, mass, shape, and/or the pressure of the stream that emerges from them. In a nozzle, the velocity of fluid increases at the expense of its pressure energy. |
orbit | Space and Astronomy | 1 | Noun:The path followed by a moon, planet or artificial satellite as it travelsaround another body in space. |
orbit phasing | Space and Astronomy | 1 | In astrodynamics, orbit phasing is the adjustment of the time-position of spacecraft along its orbit, usually described as adjusting the orbiting spacecraft's true anomaly. Orbital phasing is primarily used in scenarios where a spacecraft in a given orbit must be moved to a different location within the same orbit. The change in position within the orbit is usually defined as the phase angle, ϕ, and is the change in true anomaly required between the spacecraft's current position to the final position. |
orbital eccentricity | Space and Astronomy | 1 | In astrodynamics , the orbital eccentricity of an astronomical object is a dimensionless parameter that determines the amount by which its orbit around another body deviates from a perfect circle . A value of 0 is a circular orbit , values between 0 and 1 form an elliptic orbit , 1 is a parabolic escape orbit , and greater than 1 is a hyperbola . The term derives its name from the parameters of conic sections , as every Kepler orbit is a conic section. It is normally used for the isolated two-body problem , but extensions exist for objects following a rosette orbit through the galaxy. |
orbital elements | Space and Astronomy | 1 | are the parameters required to uniquely identify a specific orbit . In celestial mechanics these elements are considered in two-body systems using a Kepler orbit . There are many different ways to mathematically describe the same orbit, but certain schemes, each consisting of a set of six parameters, are commonly used in astronomy and orbital mechanics . A real orbit and its elements change over time due to gravitational perturbations by other objects and the effects of general relativity . A Kepler orbit is an idealized, mathematical approximation of the orbit at a particular time. |
orbital inclination | Space and Astronomy | 1 | measures the tilt of an object's orbit around a celestial body. It is expressed as the angle between a reference plane and the orbital plane or axis of direction of the orbiting object. |
orbital inclination change | Space and Astronomy | 1 | is an orbital maneuver aimed at changing the inclination of an orbiting body's orbit . This maneuver is also known as an orbital plane change as the plane of the orbit is tipped. This maneuver requires a change in the orbital velocity vector ( delta v ) at the orbital nodes (i.e. the point where the initial and desired orbits intersect, the line of orbital nodes is defined by the intersection of the two orbital planes). |
orbital maneuver | Space and Astronomy | 1 | In spaceflight , an orbital maneuver (otherwise known as a burn ) is the use of propulsion systems to change the orbit of a spacecraft . |
orbital mechanics | Space and Astronomy | 1 | or astrodynamics , is the application of ballistics and celestial mechanics to the practical problems concerning the motion of rockets and other spacecraft . The motion of these objects is usually calculated from Newton's laws of motion and law of universal gravitation . is a core discipline within space-mission design and control. |
orbital node | Space and Astronomy | 1 | is either of the two points where an orbit intersects a plane of reference to which it is inclined. A non-inclined orbit , which is contained in the reference plane, has no nodes. |
orbital period | Space and Astronomy | 1 | (also revolution period ), is the time a given astronomical object takes to complete one orbit around another object, and applies in astronomy usually to planets or asteroids orbiting the Sun , moons orbiting planets, exoplanets orbiting other stars , or binary stars . |
orbital station-keeping | Space and Astronomy | 1 | In astrodynamics , orbital station-keeping is keeping a spacecraft at a fixed distance from another spacecraft. It requires a series of orbital maneuvers made with thruster burns to keep the active craft in the same orbit as its target. For many low Earth orbit satellites, the effects of non-Keplerian forces, i.e. the deviations of the gravitational force of the Earth from that of a homogeneous sphere , gravitational forces from Sun/Moon, solar radiation pressure and air drag , must be counteracted. |
orbiter boom sensor system | Space and Astronomy | 1 | (OBSS), was a 50-foot (15.24 m) boom carried on board NASA's Space Shuttles. The boom was grappled by the Canadarm and served as an extension of the arm, doubling its length to a combined total of 100 feet (30 m). At the far end of the boom was an instrumentation package of cameras and lasers used to scan the leading edges of the wings, the nose cap, and the crew compartment after each lift-off and before each landing. If flight engineers suspected potential damage to other areas, as evidenced in imagery captured during lift-off or the rendezvous pitch maneuver, then additional regions could be scanned. |
osculating orbit | Space and Astronomy | 1 | In astronomy , and in particular in astrodynamics , the osculating orbit of an object in space at a given moment in time is the gravitational Kepler orbit (i.e. an elliptic or other conic one) that it would have around its central body if perturbations were absent. That is, it is the orbit that coincides with the current orbital state vectors (position and velocity ). |
parallel axis theorem | Space and Astronomy | 1 | also known as Huygens–Steiner theorem , or just as Steiner's theorem , named after Christiaan Huygens and Jakob Steiner , can be used to determine the moment of inertia or the second moment of area of a rigid body about any axis, given the body's moment of inertia about a parallel axis through the object's center of gravity and the perpendicular distance between the axes. |
parasitic drag | Space and Astronomy | 1 | also known as profile drag , : 254 : 256 is a type of aerodynamic drag that acts on any object when the object is moving through a fluid. is a combination of form drag and skin friction drag . : 641–642 It affects all objects regardless of whether they are capable of generating lift . Total drag on an aircraft is made up of parasitic drag and lift-induced drag . is so named because it is not useful, whereas lift-induced drag is the result of an airfoil generating lift. comprises all types of drag except lift-induced drag. |
perpendicular axes theorem | Space and Astronomy | 1 | states that the moment of inertia of a planar lamina (i.e. 2-D body) about an axis perpendicular to the plane of the lamina is equal to the sum of the moments of inertia of the lamina about the two axes at right angles to each other, in its own plane intersecting each other at the point where the perpendicular axis passes through it. |
plasma | Space and Astronomy | 1 | (physics) – (from Ancient Greek πλάσμα ' moldable substance ' ) is one of the four fundamental states of matter . It consists of a gas of ions – atoms or molecules which have at least one orbital electron stripped (or an extra electron attached) and, thus, an electric charge. It is the most abundant form of ordinary matter in the universe , being mostly associated with stars , including the Sun . It extends to the rarefied intracluster medium and possibly to intergalactic regions . |
plug nozzle | Space and Astronomy | 1 | is a type of nozzle which includes a centerbody or plug around which the working fluid flows. s have applications in aircraft, rockets, and numerous other fluid flow devices. |
radar | Space and Astronomy | 1 | system using the reflection from transmitted electromagnetic waves to detect the distance and rough shape of an object, working even in outer space , unlike sonar |
rcs | Space and Astronomy | 1 | RCS ( Reaction control system ) – set of rocket thrusters used for spacecraft maneuvers over the craft's three rotation axes in outer space |
reaction control system | Space and Astronomy | 1 | RCS ( Reaction control system ) – set of rocket thrusters used for spacecraft maneuvers over the craft's three rotation axes in outer space |
rogallo wing | Space and Astronomy | 1 | is a flexible type of wing . In 1948, Francis Rogallo , a NASA engineer, and his wife Gertrude Rogallo , invented a self-inflating flexible wing they called the Parawing , also known after them as the "Rogallo Wing" and flexible wing . NASA considered Rogallo's flexible wing as an alternative recovery system for the Mercury and Gemini space capsules , and for possible use in other spacecraft landings, but the idea was dropped from Gemini in 1964 in favor of conventional parachutes . |
scalar | Space and Astronomy | 1 | (physics) – A quantity with magnitude but no direction. |
single-stage-to-orbit | Space and Astronomy | 1 | spacecraft able to fly from a celestial body (usually the Earth or the Moon )'s surface to its orbit without using external boosters |
space shuttle | Space and Astronomy | 1 | crewed NASA spacecraft used between 1981 and 2011, consisting of a reusable spaceplane (the orbiter , capable of airplane -like landing) attached to an expendable external tank (which disintegrated during re-entry ) and two recoverable solid rocket boosters (which re-entered the Earth 's atmosphere and splash-landed) |
space shuttle external tank | Space and Astronomy | 1 | external tank attached to the orbiter and the solid rocket boosters in the NASA Space Shuttle program |
space shuttle orbiter | Space and Astronomy | 1 | reusable NASA VTHL spaceplane used during the Space Shuttle program (1981–2011) |
space station | Space and Astronomy | 1 | habitable artificial satellite |
spaceplane | Space and Astronomy | 1 | vehicle capable of both atmospheric flight according to the laws of aerodynamics (like an aircraft ) and spaceflight in outer space (like a spacecraft ) |
srb | Space and Astronomy | 1 | solid rocket booster |
ssto | Space and Astronomy | 1 | single-stage-to-orbit |
subsonic | Space and Astronomy | 1 | inferior to the speed of sound |
supersonic | Space and Astronomy | 1 | superior to the speed of sound |
terminal velocity | Space and Astronomy | 1 | is the maximum velocity (speed) attainable by an object as it falls through a fluid ( air is the most common example). It occurs when the sum of the drag force ( F d ) and the buoyancy is equal to the downward force of gravity ( F G ) acting on the object. Since the net force on the object is zero, the object has zero acceleration . |
torricelli's equation | Space and Astronomy | 1 | In physics, , or Torricelli's formula, is an equation created by Evangelista Torricelli to find the final velocity of an object moving with a constant acceleration along an axis (for example, the x axis) without having a known time interval. |
total air temperature | Space and Astronomy | 1 | In aviation, stagnation temperature is known as total air temperature and is measured by a temperature probe mounted on the surface of the aircraft. The probe is designed to bring the air to rest relative to the aircraft. As the air is brought to rest, kinetic energy is converted to internal energy . The air is compressed and experiences an adiabatic increase in temperature. Therefore, total air temperature is higher than the static (or ambient) air temperature. is an essential input to an air data computer in order to enable the computation of static air temperature and hence true airspeed . |
trajectory | Space and Astronomy | 1 | or flight path, is the path that an object with mass in motion follows through space as a function of time. In classical mechanics , a trajectory is defined by Hamiltonian mechanics via canonical coordinates ; hence, a complete trajectory is defined by position and momentum , simultaneously. The mass might be a projectile or a satellite . For example, it can be an orbit — the path of a planet , asteroid , or comet as it travels around a central mass . |
ufo | Space and Astronomy | 1 | An unidentified flying object is any perceived aerial phenomenon that cannot be immediately identified or explained. On investigation, most s are identified as known objects or atmospheric phenomena, while a small number remain unexplained. |
v-2 rocket | Space and Astronomy | 1 | The V-2 ( German : Vergeltungswaffe 2 , "Retribution Weapon 2"), with the technical name Aggregat 4 ( A4 ), was the world's first long-range guided ballistic missile . The missile, powered by a liquid-propellant rocket engine, was developed during the Second World War in Germany as a " vengeance weapon " and assigned to attack Allied cities as retaliation for the Allied bombings against German cities. The also became the first artificial object to travel into space by crossing the Kármán line with the vertical launch of MW 18014 on 20 June 1944. |
variable specific impulse magnetoplasma rocket | Space and Astronomy | 1 | (VASIMR), is an electrothermal thruster under development for possible use in spacecraft propulsion . It uses radio waves to ionize and heat an inert propellant , forming a plasma, then a magnetic field to confine and accelerate the expanding plasma , generating thrust . It is a plasma propulsion engine , one of several types of spacecraft electric propulsion systems. |
velocity | Space and Astronomy | 1 | The velocity of an object is the rate of change of its position with respect to a frame of reference , and is a function of time. is equivalent to a specification of an object's speed and direction of motion (e.g. 60 km/h to the north). is a fundamental concept in kinematics , the branch of classical mechanics that describes the motion of bodies. |
viscometer | Space and Astronomy | 1 | (also called viscosimeter ) is an instrument used to measure the viscosity of a fluid . For liquids with viscosities which vary with flow conditions , an instrument called a rheometer is used. Thus, a rheometer can be considered as a special type of viscometer. s only measure under one flow condition. |
viscosity | Space and Astronomy | 1 | The viscosity of a fluid is a measure of its resistance to deformation at a given rate. For liquids, it corresponds to the informal concept of "thickness": for example, syrup has a higher viscosity than water . |
vortex generator | Space and Astronomy | 1 | (VG), is an aerodynamic device, consisting of a small vane usually attached to a lifting surface (or airfoil , such as an aircraft wing ) or a rotor blade of a wind turbine . VGs may also be attached to some part of an aerodynamic vehicle such as an aircraft fuselage or a car. When the airfoil or the body is in motion relative to the air, the VG creates a vortex , which, by removing some part of the slow-moving boundary layer in contact with the airfoil surface, delays local flow separation and aerodynamic stalling , thereby improving the effectiveness of wings and control surfaces , such as flaps , elevators , ailerons , and rudders . |
wave drag | Space and Astronomy | 1 | In aeronautics , wave drag is a component of the aerodynamic drag on aircraft wings and fuselage, propeller blade tips and projectiles moving at transonic and supersonic speeds, due to the presence of shock waves . is independent of viscous effects , and tends to present itself as a sudden and dramatic increase in drag as the vehicle increases speed to the Critical Mach number . It is the sudden and dramatic rise of wave drag that leads to the concept of a sound barrier . |
weight | Space and Astronomy | 1 | In science and engineering , the weight of an object is the force acting on the object due to gravity . |
weight function | Space and Astronomy | 1 | is a mathematical device used when performing a sum, integral, or average to give some elements more "weight" or influence on the result than other elements in the same set. The result of this application of a weight function is a weighted sum or weighted average . s occur frequently in statistics and analysis , and are closely related to the concept of a measure . s can be employed in both discrete and continuous settings. They can be used to construct systems of calculus called "weighted calculus" and "meta-calculus". |
wind tunnels | Space and Astronomy | 1 | are large tubes with air blowing through them which are used to replicate the interaction between air and an object flying through the air or moving along the ground. Researchers use wind tunnels to learn more about how an aircraft will fly. NASA uses wind tunnels to test scale models of aircraft and spacecraft. Some wind tunnels are large enough to contain full-size versions of vehicles. The wind tunnel moves air around an object, making it seem as if the object is flying. |
wing | Space and Astronomy | 1 | is a type of fin that produces lift while moving through air or some other fluid . Accordingly, wings have streamlined cross-sections that are subject to aerodynamic forces and act as airfoils . A wing's aerodynamic efficiency is expressed as its lift-to-drag ratio . The lift a wing generates at a given speed and angle of attack can be one to two orders of magnitude greater than the total drag on the wing. A high lift-to-drag ratio requires a significantly smaller thrust to propel the wings through the air at sufficient lift. |
wright flyer | Space and Astronomy | 1 | The (the Kitty Hawk , also known as Flyer I or 1903 Flyer ) made the first sustained flight by a manned heavier-than-air powered and controlled aircraft—an airplane —on 17 December 1903. Invented and flown by Orville and Wilbur Wright , it marked the beginning of the "pioneer era" of aviation. |
wright glider | Space and Astronomy | 1 | The Wright brothers designed, built and flew a series of three manned gliders in 1900–1902 as they worked towards achieving powered flight . They also made preliminary tests with a kite in 1899. In 1911 Orville conducted tests with a much more sophisticated glider. Neither the kite nor any of the gliders were preserved, but replicas of all have been built. |
a-type star | Space and Astronomy | 1 | In the Harvard spectral classification system, a class of main-sequence star having spectra dominated by Balmer absorption lines of hydrogen. Stars of spectral class A are typically blue-white or white in color, measure between 1.4 and 2.1 times the mass of the Sun, and have surface temperatures of 7,600–10,000 kelvin. |
absolute magnitude | Space and Astronomy | 1 | A measure of a star's absolute brightness. It is defined as the apparent magnitude the star would show if it were located at a distance of 10 parsecs, or 32.6 light-years. |
accretion disk | Space and Astronomy | 1 | A roughly circular mass of diffuse material in orbit around a central object, such as a star or black hole. The material is acquired from a source external to the central object, and friction causes it to spiral inward towards the object. |
active galactic nucleus | Space and Astronomy | 1 | A compact region in the center of a galaxy displaying a much higher than normal luminosity over some part of the electromagnetic spectrum with characteristics indicating that the luminosity is not produced by stars. A galaxy hosting an AGN is called an active galaxy. |
agn | Space and Astronomy | 1 | A compact region in the center of a galaxy displaying a much higher than normal luminosity over some part of the electromagnetic spectrum with characteristics indicating that the luminosity is not produced by stars. A galaxy hosting an AGN is called an active galaxy. |
airborne observatory | Space and Astronomy | 1 | An airplane with an astronomical telescope. |
albedo | Space and Astronomy | 1 | A measure of the proportion of the total solar radiation received by an astronomical body, such as a planet, that is diffusely reflected away from the body. It is a dimensionless quantity typically measured on a scale from 0 (indicating total absorption of all incident radiation, as by a black body) to 1 (indicating total reflection). The albedo reported for an astronomical body may vary widely by the spectral and angular distribution of the incident radiation, by the "layer" of the body being measured (e.g. upper atmosphere versus surface), and by local variation within these layers (e.g. cloud cover and geological or environmental surface features). |
albedo feature | Space and Astronomy | 1 | A large area on the surface of a reflecting object that shows a significant contrast in brightness or darkness (albedo) compared to adjacent areas. |
alfvén surface | Space and Astronomy | 1 | The boundary separating a star's corona from the stellar wind defined as where the coronal plasma's Alfvén speed and the large-scale stellar wind speed are equal. |
am star | Space and Astronomy | 1 | A chemically peculiar star belonging to the more general class of A-type stars. The spectrum of the Am stars shows abnormal enhancements and deficiencies of certain metals. See metallicity. |
aphelion | Space and Astronomy | 1 | The point in the elliptical orbit of an object (such as a planet or comet) about the Sun at which the object is at its maximum distance from the Sun. |
apoapsis | Space and Astronomy | 1 | The point at which an orbiting body is furthest from its primary. Contrast periapsis. |
apogee | Space and Astronomy | 1 | The point at which a body orbiting the Earth (such as the Moon or an artificial satellite) is furthest from the Earth. Contrast perigee. |
apparent magnitude | Space and Astronomy | 1 | A measure of the brightness of a celestial body as seen by an observer on Earth, adjusted to the value it would have in the absence of the atmosphere. The brighter the object appears, the lower its magnitude. |
appulse | Space and Astronomy | 1 | The closest approach of one celestial object to another, as viewed from a third body. |
apsis | Space and Astronomy | 1 | In the orbit of a planetary body, one of the two extreme points of distance between the body and its primary – either the point of minimal distance, called the periapsis, or the point of maximal distance, called the apoapsis. The term may also be used to refer to the value of the distance rather than the point itself. All elliptical orbits have exactly two apsides. |
argument of periapsis | Space and Astronomy | 1 | The angle from an orbiting body's ascending node to its periapsis, measured in the direction of motion. It is one of six canonical orbital elements used to characterize an orbit. |
artificial satellite | Space and Astronomy | 1 | An object that has been intentionally placed into orbit by humans, often around the Earth but also around other bodies within the Solar System. Contrast natural satellite. |
ascending node | Space and Astronomy | 1 | The orbital node at which an orbiting object moves north through the plane of reference (in geocentric and heliocentric orbits) or at which the orbiting object moves away from the observer (in orbits outside of the Solar System). The position of the ascending node with respect to a reference direction, called the longitude of the ascending node, is used along with other parameters to describe an orbit. Contrast descending node. |
aspect | Space and Astronomy | 1 | The position of a planet or Earth's Moon with respect to the Sun, as viewed from Earth. |
asterism | Space and Astronomy | 1 | Any pattern of stars recognizable in Earth's night sky. An asterism may form part of an official constellation or it may be composed of stars from more than one constellation. |
asteroid | Space and Astronomy | 1 | A celestial lump, hundreds of kilometres wide, composed of rock and iron, that orbits the Sun. Most asteroidslie in a belt between the orbits of Mars and Jupiter and are thought to be left-over bits from the formation of the Solar System. |
asteroid belt | Space and Astronomy | 1 | The circumstellar disc in the Solar System located roughly between the orbits of Mars and Jupiter that is occupied by numerous irregularly shaped small Solar System bodies ranging in size from dust particles to asteroids and minor planets. The asteroid belt is often called the main asteroid belt or main belt to distinguish it from other asteroid populations in other parts of the Solar System. |
astrobiology | Space and Astronomy | 1 | An interdisciplinary field that studies the origins, evolution, distribution, and future of living systems in the universe, encompassing research on organic compounds in space, abiogenesis and extreme-environment adaptation on Earth, the habitability of extrasolar planets, the possible existence of extraterrestrial life, and how humans might be able to detect extraterrestrial biosignatures, among other topics. |
astrodynamics | Space and Astronomy | 1 | See orbital mechanics. |
astrogeology | Space and Astronomy | 1 | A field that studies the geology of solidified bodies such as the planets and their moons, asteroids, comets, and meteorites. Investigations are centered around the composition, structure, processes, and history of these objects. |
astrometric binary | Space and Astronomy | 1 | A type of binary system where evidence for an unseen orbiting companion is revealed by its periodic gravitational perturbation of the visible component. See also spectroscopic binary. |
astrometry | Space and Astronomy | 1 | The branch of astronomy that involves precise measurements of the positions and movements of stars and other celestial bodies. |
astronomical body | Space and Astronomy | 1 | A type of naturally occurring physical entity, association, or structure within the observable universe that is a single, tightly bound, contiguous structure, such as a star, planet, moon, or asteroid. Though the terms astronomical "body" and astronomical "object" are often used interchangeably, there are technical distinctions. |
astronomical catalogue | Space and Astronomy | 1 | A list of astronomical objects, typically grouped together because they share a common type, morphology, origin, means of detection, or method of discovery. |
astronomical object | Space and Astronomy | 1 | A type of naturally occurring physical entity, association, or structure that exists within the observable universe but is a more complex, less cohesively bound structure than an astronomical body, consisting perhaps of multiple bodies or even other objects with substructures, such as a planetary system, star cluster, nebula, or galaxy. Though the terms astronomical "object" and astronomical "body" are often used interchangeably, there are technical distinctions. |
astronomical symbol | Space and Astronomy | 1 | Any abstract pictorial symbol used to represent one or more astronomical objects, events, or theoretical constructs, e.g. those of the planets of the Solar System, the phases of the Moon, the zodiacal constellations, and the solstices and equinoxes. Many of these symbols were commonly used historically, though in the modern era they are usually limited to almanacs and astrology, and their appearance in scientific literature has become increasingly infrequent. Exceptions include the symbols for the Sun (☉), the Earth (🜨), and the Moon (☾), which are sometimes used for astronomical constants and in other forms of shorthand. |
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