1998 WW₃₁ (also written 1998 WW31) is an object of the solar system located beyond the orbit of Neptune. It was discovered in 1998 by the Deep Ecliptic Survey. It forms a binary system with another object with the IAU provisional designation S/2000 (1998 WW31) 1; the combined system was the first trans-Neptunian binary to be discovered. The Deep Ecliptic Survey is a project to find Kuiper belt objects, using the facilities of the National Optical Astronomy Observatory. ... November 18 is the 322nd day of the year (323rd in leap years), with 43 remaining. ... 1998 is a common year starting on Thursday of the Gregorian calendar, and was designated the International Year of the Ocean. ... The provisional designation of comets and asteroids are similar to each other: they both follow a pattern set in 1925 by the Minor Planet Center of the IAU. Historical designations At first, astronomers strove to assign symbols to the minor planets: 1 Ceres a stylized sickle 2 Pallas a lozenge... Minor planets, or planetoids are minor bodies of the solar system orbiting the sun that are larger than meteoroids (the largest of which might be taken to be around 10 meters or so across) but smaller than major planets (Mercury having a diameter of about 4880 km). ... A trans-Neptunian object (TNO) is any object in the solar system with all or most of its orbit beyond that of Neptune. ... In astronomy, an epoch is a moment in time for which celestial coordinates or orbital elements are specified. ... January 30 is the 30th day of the year in the Gregorian Calendar. ... 2005 is a common year starting on Saturday of the Gregorian calendar and is the current year. ... The Julian day or Julian day number (JDN) is the number of SI days that have elapsed since 12 noon Greenwich Mean Time (UT or TT) on Monday, January 1, 4713 BC in the proleptic Julian calendar 1. ... In astrodynamics, under standard assumptions any orbit must be of conic section shape. ... In geometry, the semi-major axis (also semimajor axis) a applies to ellipses and hyperbolas. ... The astronomical unit (AU or au or a. ... This article is about several astronomical terms (apogee & perigee, aphelion & perihelion, generic equivalents based on apsis, and related but rarer terms. ... This article is about several astronomical terms (apogee & perigee, aphelion & perihelion, generic equivalents based on apsis, and related but rarer terms. ... The orbital period is the time it takes a planet (or another object) to make one full orbit. ... A year is the time between two recurrences of an event related to the orbit of the Earth around the Sun. ... The orbital speed of a body, generally a planet, a natural satellite, an artificial satellite, or a multiple star, is the speed at which it orbits around the barycenter of a system, usually around a more massive body. ... Inclination is one of the six orbital parameters describing the shape and orientation of a celestial orbit and is the angular distance of the orbital plane from the plane of the reference (usually planets equator or the ecliptic), stated in degrees. ... A degree (or in full a degree of arc), usually symbolized °, is a measurement of plane angle, representing 1/360 of a full rotation. ... The Longitude of the ascending node () is one of the orbital elements used to specify the orbit of an object in space. ... The argument of the perihelion is one of the orbital elements describing the orbit of a planet. ... In the study of orbital dynamics the mean anomaly is a measure of time, specific to the orbiting body p, which is a multiple of 2π radians at and only at periapsis. ... Mass is a property of physical objects that, roughly speaking, measures the amount of matter they contain. ... The international prototype, made of platinum-iridium, which is kept at the BIPM under conditions specified by the 1st CGPM in 1889. ... Density (symbol: ρ - Greek: rho) is a measure of mass per unit of volume. ... A cubic centimetre (cm3) is an SI derived unit of volume, equal to the volume of a cube with side length of 1 centi metre. ... It has been suggested that Law of universal gravitation be merged into this article or section. ... In physics, for a given gravitational field and a given position, the escape velocity is the minimum speed an object without propulsion, at that position, needs to have to move away indefinitely from the source of the field, as opposed to falling back or staying in an orbit within a... In astronomy, a rotation period is the time an astronomical object takes to complete one revolution around its rotation axis. ... An asteroid is a small, solid object in our Solar System, orbiting the Sun. ... In astronomy, absolute magnitude is the apparent magnitude, m, an object would have if it were at a standardized distance away. ... The albedo is a measure of reflectivity of a surface or body. ... Temperature is the physical property of a system which underlies the common notions of hot and cold; the material with the higher temperature is said to be hotter. ... The kelvin (symbol: K) is the SI unit of temperature, and is one of the seven SI base units. ... Presentation of the solar system (not to scale) The solar system consists of the Sun and all the objects that orbit around it, including meteoroids, planetoids, comets, moons, and planets. ... A trans-Neptunian object (TNO) is any object in the solar system with all or most of its orbit beyond that of Neptune. ... 1998 is a common year starting on Thursday of the Gregorian calendar, and was designated the International Year of the Ocean. ... The Deep Ecliptic Survey is a project to find Kuiper belt objects, using the facilities of the National Optical Astronomy Observatory. ... A binary system is an astronomy term referring to two objects in space, usually stars, which are so close that their gravitational forces attract one another into a mutual orbit. ... IAU is a three-letter acronym that denotes: International Astronomical Union International American University International Association of Universities International Association of Ultra Runners for ultramarathoners. ... The provisional designation of comets and asteroids are similar to each other: they both follow a pattern set in 1925 by the Minor Planet Center of the IAU. Historical designations At first, astronomers strove to assign symbols to the minor planets: 1 Ceres a stylized sickle 2 Pallas a lozenge... A trans-Neptunian object (TNO) is any object in the solar system with all or most of its orbit beyond that of Neptune. ...

External links

• The IAU circular announcing the discovery of the companion