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Pluto Pluto Pluto (minorplanet designation: 134340 Pluto) is a dwarf planet in the Kuiper belt, a ring of bodies beyond Neptune. It was the first Kuiper belt Kuiper belt object to be discovered. Pluto Pluto was discovered by Clyde Tombaugh Clyde Tombaugh in 1930 and was originally considered to be the ninth planet from the Sun. After 1992, its status as a planet was questioned following the discovery of several objects of similar size in the Kuiper belt. In 2005, Eris, a dwarf planet in the scattered disc which is 27% more massive than Pluto, was discovered. This led the International Astronomical Union International Astronomical Union (IAU) to define the term "planet" formally in 2006, during their 26th General Assembly [...More...]  "Pluto" on: Wikipedia Yahoo 

Flattening Flattening Flattening is a measure of the compression of a circle or sphere along a diameter to form an ellipse or an ellipsoid of revolution (spheroid) respectively. Other terms used are ellipticity, or oblateness. The usual notation for flattening is f and its definition in terms of the semiaxes of the resulting ellipse or ellipsoid is f l a t t e n i n g = f = a − b a . displaystyle mathrm flattening =f= frac ab a . The compression factor is b/a in each case. For the ellipse, this factor is also the aspect ratio of the ellipse. There are two other variants of flattening (see below) and when it is necessary to avoid confusion the above flattening is called the first flattening [...More...]  "Flattening" on: Wikipedia Yahoo 

Earth Radius Earth Earth radius is the approximate distance from Earth's center to its surface, about 6,371 km (3,959 mi). This distance is used as a unit of length, especially in astronomy and geophysics, where it is usually denoted by R⊕. Strictly speaking, the term "radius" is a property of a true sphere. Since Earth Earth is only approximately spherical, no single value serves as its definitive radius. Meaningful values range from 6,353 to 6,384 kilometres (3,948 to 3,967 mi). A distance from the center of Earth Earth to some point on its surface might be referred to as Earth’s radius at that point. More commonly, Earth radius means a computed average of distances to the surface or to some idealized surface [...More...]  "Earth Radius" on: Wikipedia Yahoo 

Volume Volume Volume is the quantity of threedimensional space enclosed by a closed surface, for example, the space that a substance (solid, liquid, gas, or plasma) or shape occupies or contains.[1] Volume Volume is often quantified numerically using the SI derived unit, the cubic metre. The volume of a container is generally understood to be the capacity of the container; i. e., the amount of fluid (gas or liquid) that the container could hold, rather than the amount of space the container itself displaces. Three dimensional mathematical shapes are also assigned volumes. Volumes of some simple shapes, such as regular, straightedged, and circular shapes can be easily calculated using arithmetic formulas [...More...]  "Volume" on: Wikipedia Yahoo 

Argument Of Periapsis The argument of periapsis (also called argument of perifocus or argument of pericenter), symbolized as ω, is one of the orbital elements of an orbiting body. Parametrically, ω is the angle from the body's ascending node to its periapsis, measured in the direction of motion. For specific types of orbits, words such as perihelion (for heliocentric orbits), perigee (for geocentric orbits), periastron (for orbits around stars), and so on may replace the word periapsis. (See apsis for more information.) An argument of periapsis of 0° means that the orbiting body will be at its closest approach to the central body at the same moment that it crosses the plane of reference from South to North. An argument of periapsis of 90° means that the orbiting body will reach periapsis at its northmost distance from the plane of reference. Adding the argument of periapsis to the longitude of the ascending node gives the longitude of the periapsis [...More...]  "Argument Of Periapsis" on: Wikipedia Yahoo 

Longitude Of The Ascending Node The longitude of the ascending node (☊ or Ω) is one of the orbital elements used to specify the orbit of an object in space. It is the angle from a reference direction, called the origin of longitude, to the direction of the ascending node, measured in a reference plane.[1] The ascending node is the point where the orbit of the object passes through the plane of reference, as seen in the adjacent image. Commonly used reference planes and origins of longitude include:For a geocentric orbit, Earth's equatorial plane as the reference plane, and the First Point of Aries First Point of Aries as the origin of longitude. In this case, the longitude is also called the right ascension of the ascending node, or RAAN [...More...]  "Longitude Of The Ascending Node" on: Wikipedia Yahoo 

Mass Mass Mass is both a property of a physical body and a measure of its resistance to acceleration (a change in its state of motion) when a net force is applied.[1] It also determines the strength of its mutual gravitational attraction to other bodies. The basic SI unit SI unit of mass is the kilogram (kg). In physics, mass is not the same as weight, even though mass is often determined by measuring the object's weight using a spring scale, rather than balance scale comparing it directly with known masses. An object on the Moon Moon would weigh less than it does on Earth Earth because of the lower gravity, but it would still have the same mass. This is because weight is a force, while mass is the property that (along with gravity) determines the strength of this force. In Newtonian physics, mass can be generalized as the amount of matter in an object [...More...]  "Mass" on: Wikipedia Yahoo 

Degree (angle) A degree (in full, a degree of arc, arc degree, or arcdegree), usually denoted by ° (the degree symbol), is a measurement of a plane angle, defined so that a full rotation is 360 degrees. It is not an SI unit, as the SI unit SI unit of angular measure is the radian, but it is mentioned in the SI brochure as an accepted unit.[4] Because a full rotation equals 2π radians, one degree is equivalent to π/180 radians.Contents1 History 2 Subdivisions 3 Alternative units 4 See also 5 Notes 6 References 7 External linksHistory[edit] See also: DecansA circle with an equilateral chord (red). One sixtieth of this arc is a degree. Six such chords complete the circle.The original motivation for choosing the degree as a unit of rotations and angles is unknown [...More...]  "Degree (angle)" on: Wikipedia Yahoo 

Mean Anomaly In celestial mechanics, the mean anomaly is an angle used in calculating the position of a body in an elliptical orbit in the classical twobody problem. It is the angular distance from the pericenter which a fictitious body would have if it moved in a circular orbit, with constant speed, in the same orbital period as the actual body in its elliptical orbit.[1][2]Contents1 Definition 2 Formula 3 See also 4 References 5 External linksDefinition[edit] Define T as the time required for a particular body to complete one orbit [...More...]  "Mean Anomaly" on: Wikipedia Yahoo 

Orbital Speed In gravitationally bound systems, the orbital speed of an astronomical body or object (e.g. planet, moon, artificial satellite, spacecraft, or star) is the speed at which it orbits around either the barycenter or, if the object is much less massive than the largest body in the system, its speed relative to that largest body. The speed in this latter case may be relative to the surface of the larger body or relative to its center of mass. The term can be used to refer to either the mean orbital speed, i.e. the average speed over an entire orbit, or its instantaneous speed at a particular point in its orbit. Maximum (instantaneous) orbital speed occurs at periapsis (perigee, perhelion, etc.), while minimum speed for objects in closed orbits occurs at apoapsis (aphelion, apogee, etc.) [...More...]  "Orbital Speed" on: Wikipedia Yahoo 

Julian Year (astronomy) In astronomy, a Julian year (symbol: a) is a unit of measurement of time defined as exactly 365.25 days of 7004864000000000000♠86400 SI seconds each.[1][2][3][4] The length of the Julian year is the average length of the year in the Julian calendar Julian calendar that was used in Western societies until some centuries ago, and from which the unit is named. Nevertheless, because astronomical Julian years are measuring duration rather than designating dates, this Julian year does not correspond to years in the Julian calendar Julian calendar or any other calendar [...More...]  "Julian Year (astronomy)" on: Wikipedia Yahoo 

Earth Mass Earth Earth mass (M⊕, where ⊕ is the standard astronomical symbol for planet Earth) is the unit of mass equal to that of Earth. This value includes the atmosphere but excludes the moon [...More...]  "Earth Mass" on: Wikipedia Yahoo 

Semimajor And Semiminor Axes In geometry, the major axis of an ellipse is its longest diameter: a line segment that runs through the center and both foci, with ends at the widest points of the perimeter. The semimajor axis is one half of the major axis, and thus runs from the centre, through a focus, and to the perimeter [...More...]  "Semimajor And Semiminor Axes" on: Wikipedia Yahoo 

Perihelion And Aphelion The perihelion (/ˌpɛrɪˈhiːliən/) of any orbit of a celestial body about the Sun Sun is the point where the body comes nearest to the Sun. It is the opposite of aphelion (/æpˈhiːliən/), which is the point in the orbit where the celestial body is farthest from the Sun.[1] Apogee Apogee means it is the moon far from earth Perigee Perigee means that the moon is near earthContents1 Etymology 2 Astronomical meaning 3 Application to Earth 4 See also 5 References 6 External linksEtymology[edit] The words perihelion and aphelion were coined by Johannes Kepler[2] to describe the orbital motion of the planets [...More...]  "Perihelion And Aphelion" on: Wikipedia Yahoo 

Acceleration In physics, acceleration is the rate of change of velocity of an object with respect to time. An object's acceleration is the net result of any and all forces acting on the object, as described by Newton's Second Second Law.[1] The SI unit SI unit for acceleration is metre per second squared (m s−2). Accelerations are vector quantities (they have magnitude and direction) and add according to the parallelogram law.[2][3] As a vector, the calculated net force is equal to the product of the object's mass (a scalar quantity) and its acceleration. For example, when a car starts from a standstill (zero relative velocity) and travels in a straight line at increasing speeds, it is accelerating in the direction of travel. If the car turns, an acceleration occurs toward the new direction [...More...]  "Acceleration" on: Wikipedia Yahoo 

J2000 In astronomy, an epoch is a moment in time used as a reference point for some timevarying astronomical quantity, such as the celestial coordinates or elliptical orbital elements of a celestial body, because these are subject to perturbations and vary with time.[1] These timevarying astronomical quantities might include, for example, the mean longitude or mean anomaly of a body, the node of its orbit relative to a reference plane, the direction of the apogee or aphelion of its orbit, or the size of the major axis of its orbit. The main use of astronomical quantities specified in this way is to calculate other relevant parameters of motion, in order to predict future positions and velocities [...More...]  "J2000" on: Wikipedia Yahoo 