Pluto

Click image for description Explanation: Pluto is mostly brown. ...
Discovery
Discovered by	Clyde W. Tombaugh
Discovered on	February 18, 1930
Orbital characteristics (Epoch J2000)
Semi-major axis	5,906,376,272 km 39.481 686 77 AU
Orbital circumference	36.530 Tm 244.186 AU
Eccentricity	0.248 807 66
Perihelion	4,436,824,613 km 29.658 340 67 AU
Aphelion	7,375,927,931 km 49.305 032 87 AU
Orbital period	90,613.3058 d (248.09 a)
Synodic period	366.74 d
Avg. Orbital Speed	4.666 km/s
Max. Orbital Speed	6.112 km/s
Min. Orbital Speed	3.676 km/s
Inclination	17.141 75° (11.88° to Sun's equator)
Longitude of the ascending node	110.303 47°
Argument of the perihelion	113.763 29°
Number of satellites	1
Physical characteristics
Diameter	2390 km (0.180 Earths or 1,485 miles)
Surface area	1.795×107 km2 (0.033 Earths)
Volume	7.15×109 km3 (0.0066 Earths)
Mass	1.25×1022 kg (0.0021 Earths)
Mean density	1.750 g/cm3
Equatorial gravity	0.58 m/s2 (0.059 gee)
Escape velocity	1.2 km/s
Rotation period	6.387 d (6 d 9 h 17.6 min)
Rotation velocity	47.18 km/h (at the equator)
Axial tilt	122.54° (to orbit) 115.60° (to the ecliptic)[1]
Right ascension of North pole	133.02° (8 h 52 min 5 s)
Declination	-9.09°
Albedo	0.30
Surface temp.	min mean max 33 K 44 K 55 K
Atmospheric characteristics
Atmospheric pressure	0.15-0.30 pascals
Composition	nitrogen, methane

Pluto is the ninth planet from the Sun. Discovered in 1930, Pluto is the smallest planet in our solar system and has a highly eccentric orbit which is highly inclined in respect to the other planets, and takes it inside the orbit of Neptune. It has one moon, Charon. Pluto's symbol is a combination of the name's first two letters, "P-L", which are also Percival Lowell's initials (Unicode: ♇ ), although some prefer a different symbol resembling that of Neptune but with a circle in the top center instead of the middle spoke. Clyde William Tombaugh (February 4, 1906 – January 17, 1997) was an American astronomer who discovered the planet Pluto in 1930. ... February 18 is the 49th day of the year in the Gregorian Calendar. ... 1930 is a common year starting on Wednesday. ... In physics, an orbit is the path that an object makes, around another object, whilst under the influence of a source of centripetal force, such as gravity. ... In astronomy, an epoch is a moment in time for which celestial coordinates or orbital elements are specified. ... The J2000. ... In geometry, the term semi-major axis (also semimajor axis) is used to describe the dimensions of ellipses and hyperbolas. ... A kilometre (American spelling: kilometer, symbol: km) is a unit of length equal to 1000 metres (from the Greek words khilia = thousand and metro = count/measure). ... The astronomical unit (AU or au or a. ... The circumference is the distance around a closed curve. ... Tera (symbol: T) is a prefix in the SI system of units denoting 1012, or 1 000 000 000 000. ... The metre is the basic unit of length in the International System of Units (SI: Système International dUnités). ... (This page refers to eccitricity in astrodynamics. ... 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 Julian year is the length of an average year in the Julian calendar, 365. ... The orbital period is the time it takes a planet (or another object) to make one full orbit. ... 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. ... 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. ... Moons of solar system scaled to Earths Moon The common noun moon (not capitalized) is used to mean any natural satellite of the other planets. ... For the authentication, authorisation, and accounting protocol, see DIAMETER. In geometry, a diameter (Greek words diairo = divide and metro = measure) of a circle is any straight line segment that passes through the center and whose endpoints are on the circular boundary, or, in more modern usage, the length of such... To help compare different orders of magnitude this page lists lengths between 106 and 107 m (1,000 and 10,000 km). ... This article explains the meaning of area as a physical quantity. ... (Redirected from 1 E13 m2) To help compare sizes of different areas, here is a list of areas between 10 million km² and 100 million km². ... Square kilometre (US spelling: Square kilometer), symbol km², is an SI unit of surface area. ... Volume (also called capacity) is a quantification of how much space an object occupies. ... A cubic kilometre (symbol km³) is an SI derived unit of volume. ... Mass is a property of physical objects that, roughly speaking, measures the amount of matter they contain. ... (Redirected from 1 E22 kg) Categories: Orders of magnitude (mass) ... Scientific notation is a convenient way to write very large and very small numbers. ... 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. ... It has been suggested that Law of universal gravitation be merged into this article or section. ... Acceleration is the time rate of change of velocity, and at any point on a v-t graph, it is given by the gradient of the tangent to that point In physics, acceleration (symbol: a) is defined as the rate of change (or time derivative) of velocity. ... g (also gee, g-force or g-load) is a non-SI unit of acceleration defined as exactly 9. ... 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... Axial tilt is an astronomical term regarding the inclination angle of a planets rotational axis in relation to its orbital plane. ... The plane of the Ecliptic is well seen in this picture from the 1994 lunar prospecting Clementine spacecraft. ... Right ascension (RA; symbol α: Greek letter alpha) is the astronomical term for one of the two coordinates of a point on the celestial sphere when using the equatorial coordinate system. ... In astronomy declination (dec) is one of the two coordinates of the equatorial coordinate system, the other being either right ascension or hour angle. ... 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. ... To help compare different orders of magnitude this page lists temperatures between 10 kelvins and 100 kelvins. ... Atmosphere is the general name for a layer of gases that may surround a material body of sufficient mass. ... diurnal (daily) rhythm of air pressure in northern Germany (black curve is air pressure) Atmospheric pressure is the pressure above any area in the Earths atmosphere caused by the weight of air. ... The pascal (symbol Pa) is the SI unit of pressure. ... Composition deals with the bits and pieces that make up things. ... General Name, Symbol, Number nitrogen, N, 7 Chemical series nonmetals Group, Period, Block 15, 2, p Appearance colorless Atomic mass 14. ... The simplest hydrocarbon, methane, is a gas with a chemical formula of CH4. ... A planet (from the Greek πλανήτης, planÄ“tÄ“s which means wanderer or more forcefully vagrant, tramp) is an object in orbit around a star that is not a star in its own right. ... The Sun is the star at the centre of our Solar system. ... 1930 is a common year starting on Wednesday. ... Presentation of the Solar system (not to scale). ... Atmospheric characteristics Surface pressure ≫100 MPa Hydrogen - H2 80% ±3. ... Charon (shair-un or kair-un, Greek Χάρων) is the only known satellite of Pluto. ... Percival observing Mars from the Lowell Observatory. ... In computing, Unicode provides an international standard which has the goal of providing the means to encode the text of every document people want to store on computers. ...

Due to its size and unusual orbit, there has been debate regarding whether Pluto should be classified as a planet. As of July 31, 2005, at least one other trans-Neptunian object (2003 UB₃₁₃) has been found that is larger. July 31 is the 212th day (213th in leap years) of the year in the Gregorian Calendar, with 153 days remaining, as the final day of July. ... 2005 is a common year starting on Saturday of the Gregorian calendar and is the current year. ... The title of this article is incorrect due to technical limitations. ...

Discovery and naming

Pluto was discovered by the astronomer Clyde Tombaugh at the Lowell Observatory in Arizona on February 18, 1930 when he compared photographic plates taken on January 23 and 29. After the observatory obtained confirming photographs, the news of the discovery was telegraphed to the Harvard College Observatory on March 13, 1930. The planet was later found on photographs dating back to March 19, 1915. Tombaugh was searching for a "Planet X" to explain discrepancies in the predicted orbit of Neptune. It is now known these discrepancies were an artifact of the slightly incorrect value then known for the mass of Neptune. Clyde William Tombaugh (February 4, 1906 – January 17, 1997) was an American astronomer who discovered the planet Pluto in 1930. ... Percival observing Mars from the Clark telescope at the Lowell Observatory. ... State nickname: The Grand Canyon State, The Copper State Other U.S. States Capital Phoenix Largest city Phoenix Governor Janet Napolitano (D) Official languages English Only State Area 295,254 km² (6th)  - Land 294,312 km²  - Water 942 km² (0. ... February 18 is the 49th day of the year in the Gregorian Calendar. ... 1930 is a common year starting on Wednesday. ... January 23 is the 23rd day of the year in the Gregorian Calendar. ... January 29 is the 29th day of the year in the Gregorian Calendar. ... March 13 is the 72nd day of the year in the Gregorian calendar (73rd in leap years). ... 1930 is a common year starting on Wednesday. ... March 19 is the 78th day of the year in the Gregorian calendar (79th in leap years). ... 1915 was a common year starting on Friday (see link for calendar). ... Planet X is a large hypothetical planet orbiting beyond the orbit of Neptune. ... Atmospheric characteristics Surface pressure ≫100 MPa Hydrogen - H2 80% ±3. ...

In the matter of Pluto the discretion of naming the new object belonged to Lowell Observatory and its director, Vesto Melvin Slipher, who, in the words of Tombaugh, was "urged to suggest a name for the new planet before someone else did". Soon suggestions began to pour in from all over the world. Constance Lowell, Percival's widow who had delayed the search through her lawsuit, proposed Zeus, then Lowell, and finally her own first name, none of which met with any enthusiasm. One young couple even wrote to ask that the planet be named after their newborn child. Mythological names were much to the fore: Cronus and Minerva (proposed by the New York Times, unaware that it had been proposed for Uranus some 150 years earlier) were high on the list. Also there were Artemis, Athene, Atlas, Cosmos, Hera, Hercules, Icarus, Idana, Odin, Pax, Persephone, Perseus, Prometheus, Tantalus, Vulcan, Zymal, and many more. One complication was that many of the mythological names had already been allotted to the numerous asteroids. Virtually all the female names had been used up, and male names were usually reserved for objects with unusual orbits. Vesto Melvin Slipher (November 11, 1875 – November 8, 1969) was an American astronomer. ... Percival observing Mars from the Lowell Observatory. ... Statue of Zeus The Greek sculptor Phidias created the 12-m (40-ft) tall Statue of Zeus in about 435 bc. ... Rhea tricking Cronus with a wrapped stone. ... Minerva was a Roman goddess of crafts and wisdom. ... The New York Times is an internationally known daily newspaper published in New York City and distributed in the United States and many other nations worldwide. ... Atmospheric characteristics Atmospheric pressure 120 kPa Hydrogen 83% Helium 15% Methane 1. ... This article is about the Greek goddess. ... This article is about the goddess Athena. ... In Greek mythology, Atlas was the son of the Titan Iapetus and the nymph Clymene, and brother of Prometheus. ... The cosmos is thought of as an orderly or harmonious system. ... In the Olympian pantheon of classical Greek Mythology, Hêra (Greek or ) was the wife and sister of Zeus. ... Hercules and Cacus, by Baccio Bandinelli, 1525 - 1534. ... Icarus and Daedalus In Greek mythology, Icarus was the son of Daedalus. ... Odin is considered to be the supreme god of late Germanic and Norse mythology. ... In Roman mythology, Pax (Latin for peace) (she had the greek equivalent Eirine) was recognized as a goddess during the rule of Augustus. ... Bust of Persephone In Greek mythology, Persephone (Greek Περσεφόνη, Classical Greek PersephónÄ“, Modern Greek Persefóni) was the queen of the Underworld, the Kore or young maiden, and the daughter of Demeter. ... Perseus was the son of Danae, the only child of Acrisius king of Argos. ... This article is about the mythological figure. ... This article is about Tantalus from Greek mythology. ... Vulcan, in Roman mythology, is the son of Jupiter and Juno, and husband of Maia and Venus. ... An asteroid is a small, solid object in our Solar System, orbiting the Sun. ...

The name retained for the planet is that of the Roman god Pluto, and it is also intended to evoke the initials of the astronomer Percival Lowell, who predicted that a planet would be found beyond Neptune. The name was first suggested by Venetia Burney, at the time an eleven-year-old girl from Oxford, England. Over the breakfast table, one morning her grandfather, who worked at Oxford University's Bodleian Library, was reading about the discovery of the new planet in the Times newspaper. He asked his grandaughter what she thought would be good name for it. Venetia thought that as it was so cold and so distant it should be named after the Roman God of the underworld. Professor Herbert Hall Turner cabled his colleagues in America with this suggestion, and after favourable consideration which was almost unanimous, the name Pluto was officially adopted and an announcement made by Slipher on May 1, 1930. Roman mythology can be considered as two parts. ... Pluto is an alternate name for the Greek god Hades, but was more often used in Roman mythology in their presentation of the god of the underworld, also known as Dis. ... Percival observing Mars from the Lowell Observatory. ... Venetia Burney (born 1919) was the first person to suggest the name Pluto for the planet discovered by Clyde W. Tombaugh in 1930. ... Oxford is a city and local government district in Oxfordshire, England, with a population of 134,248 ( 2001 census). ... Royal motto: Dieu et mon droit (French: God and my right) Englands location within the UK Official language English de facto Capital London de facto Largest city London Area  - Total Ranked 1st UK 130,395 km² Population  - Total (2001)  - Density Ranked 1st UK 49,138,831 377/km² Ethnicity... The University of Oxford, located in the city of Oxford in England, is the oldest university in the English-speaking world. ... Entrance to the Library, with the coats-of-arms of several Oxford colleges Oxford University Libraries Service (OULS) comprises over 30 of the University of Oxfords central and faculty libraries: from the world-famous Bodleian Library, established 400 years ago, to the modern digital library ventures. ... Many newspapers use the name Times, the most famous of which are The Times of London and the New York Times. ... Herbert Hall Turner (August 13, 1861 – August 20, 1930) was a British astronomer and seismologist. ... May 1 is the 121st day of the year in the Gregorian calendar (122nd in leap years). ... 1930 is a common year starting on Wednesday. ...

Physical characteristics

Mass and size

Pluto is not only smaller and much less massive than every other planet, it is also smaller and less massive than seven moons: Ganymede, Titan, Callisto, Io, Earth's Moon, Europa and Triton. However, Pluto is more than an order of magnitude larger than any minor planet in the asteroid belt, and it was larger than any other object known in the trans-Neptunian Kuiper belt until 2003 UB₃₁₃ was announced in 2005. See List of solar system objects by mass and List of solar system objects by radius. Moons of solar system scaled to Earths Moon The common noun moon (not capitalized) is used to mean any natural satellite of the other planets. ... Atmospheric characteristics Atmospheric pressure trace Oxygen 100% Ganymede (IPA: , gan-i-meed, Greek Γανυμήδης) is Jupiters largest moon, and indeed the largest moon in the entire solar system; it is larger in diameter than Mercury but only about half its mass. ... Titan (tye-tun, Greek Τιτάνας) is the largest moon of Saturn and the second largest moon in the solar system[1], after Jupiters moon Ganymede. ... Atmospheric characteristics Atmospheric pressure trace Carbon dioxide 100% Callisto (ka-lis-toe, Greek Καλλιστώ) is a moon of the planet Jupiter, discovered in 1610 by Galileo Galilei. ... Atmospheric characteristics Atmospheric pressure trace Sulfur dioxide 90% Io (eye-oe, Greek Ιώ) is the innermost of the four Galilean moons of Jupiter. ... Crust composition Oxygen 43% Silicon 21% Aluminium 10% Calcium 9% Iron 9% Magnesium 5% Titanium 2% Nickel 0. ... Atmospheric characteristics Atmospheric pressure 1 µPa Oxygen 100% Europa (ew-roe-pa, /juro:pa/   listen?, Greek Ευρώπη) is a moon of the planet Jupiter, smallest of the four Galilean moons. ... Triton (trye-tun, Greek Τρίτων) is the planet Neptunes largest moon, discovered by William Lassell on 1846-10-10, just 17 days after the planet itself was discovered. ... 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). ... Image of the main asteroid belt between the orbits of Mars and Jupiter. ... Artists rendering of the Kuiper Belt and more distant Oort cloud. ... The title of this article is incorrect due to technical limitations. ... 2005 is a common year starting on Saturday of the Gregorian calendar and is the current year. ... This is a list of Solar system objects by mass, in decreasing order. ... This is a list of solar system objects by radius, in decreasing order. ...

Pluto's mass and diameter could only be estimated for many decades after its discovery. The discovery of its satellite Charon in 1978 enabled a determination of the mass of the Pluto-Charon system by simple application of Newton's formulation of Kepler's third law. Later Pluto's diameter was measured when it was occulted by Charon, and its disk can now be resolved by telescopes using adaptive optics. Charon (shair-un or kair-un, Greek Χάρων) is the only known satellite of Pluto. ... 1978 was a common year starting on Sunday (the link is to a full 1978 calendar). ... Johannes Keplers primary contributions to astronomy/astrophysics were his three laws of planetary motion. ... In this July, 1997 still frame captured from video, the bright star Aldebaran has just reappeared on the dark limb of the waning crescent moon in this predawn occultation. ... Adaptive optics is a technology to improve the performance of reflecting telescopes by reducing the effects of atmospheric distortion, or twinkling. ...

Eccentric orbit

Pluto's highly eccentric orbit makes it the eighth-most distant planet from the Sun for part of each orbit; this most recently occurred from February 7, 1979 through February 11, 1999. Pluto orbits in a 3:2 orbital resonance with Neptune. When Neptune approaches Pluto from behind their gravity start to pull on each other slightly, resulting in an interaction between their positions in orbit of the same sort that produces Trojan points. Since the orbits are eccentric, the 3:2 periodic ratio is favoured because this means Neptune always passes Pluto when they're almost farthest apart. Half a Pluto orbit later, when Pluto is nearing its closest approach, it initially seems as if Neptune is about to catch up to Pluto. But Pluto speeds up due to the gravitational acceleration from the Sun, stays ahead of Neptune, and pulls ahead until they meet again on the other side of Pluto's orbit. The Sun is the star at the centre of our Solar system. ... In physics, an orbit is the path that an object makes, around another object, whilst under the influence of a source of centripetal force, such as gravity. ... February 7 is the 38th day of the year in the Gregorian Calendar. ... 1979 is a common year starting on Monday. ... February 11 is the 42nd day of the year in the Gregorian Calendar. ... 1999 is a common year starting on Friday of the Common Era, and was designated the International Year of Older Persons by the United Nations. ... Orbital Resonance is also the title of a science fiction novel by John Barnes. ... In celestial mechanics, the Lagrangian points, (also Lagrange point, L-point, or libration point) are the five stationary solutions of the circular restricted three-body problem. ...

Because of its small size and eccentric orbit, there has been some debate over whether it truly should be classified as a planet. There is mounting evidence that Pluto may in fact be a member of the Kuiper belt, only one of a large number of distant icy bodies. A subclass of such objects have been dubbed plutinos, after Pluto. Artists rendering of the Kuiper Belt and more distant Oort cloud. ... In astronomy, a plutino is a Pluto-like object, insofar as it has the same relative orbit as Pluto. ...

Atmosphere

Pluto has an atmosphere when it is close to perihelion; the atmosphere may freeze out as Pluto moves farther from the Sun. It is thought by some that Pluto shares its atmosphere with its moon. Pluto was found to have an atmosphere from an occultation observation in 1988. When a planet or asteroid occults a star, if it has no atmosphere, the star abruptly disappears. In the case of Pluto, the star dimmed out gradually. From the rate of dimming, the atmosphere was determined to have a pressure of 0.15 pascal (Pa). This thin atmosphere is most likely nitrogen and carbon monoxide, in equilibrium with solid nitrogen and carbon monoxide ices on the surface. This article is about several astronomical terms (apogee & perigee, aphelion & perihelion, generic equivalents based on apsis, and related but rarer terms. ... In this July, 1997 still frame captured from video, the bright star Aldebaran has just reappeared on the dark limb of the waning crescent moon in this predawn occultation. ... 1988 is a leap year starting on a Friday of the Gregorian calendar. ... The pascal (symbol Pa) is the SI unit of pressure. ... General Name, Symbol, Number nitrogen, N, 7 Chemical series nonmetals Group, Period, Block 15, 2, p Appearance colorless Atomic mass 14. ...

In 2003, another occultation of a star by Pluto was observed and analyzed by teams led by Bruno Sicardy [2] and by Jim Elliot. Surprisingly, the atmosphere was estimated to have a pressure of 0.3 Pa, even though Pluto was farther away from the Sun than in 1988, and hence should be colder and have a less dense atmosphere. The current best hypothesis is that the south pole of Pluto came out of shadow in 1987 (for the first time in 120 years), and extra nitrogen sublimated from a polar cap. It will take decades for the excess nitrogen to condense out of the atmosphere. 2003 is a common year starting on Wednesday of the Gregorian calendar. ... The Sun is the star at the centre of our Solar system. ... 1987 is a common year starting on Thursday of the Gregorian calendar. ...

Appearance

Pluto's apparent magnitude is fainter than 14 m and therefore a telescope larger than 30 centimetres (12 inches) is required for observation. It looks star-like even in very big telescopes, because its angular diameter is only 0.15″. The colour of Pluto is yellow. The apparent magnitude (m) of a star, planet or other heavenly body is a measure of its apparent brightness; that is, the amount of light received from the object. ...

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September 24 is the 267th day of the year (268th in leap years). ... 2015 is a common year starting on Thursday of the Gregorian calendar. ... January 6 is the 6th day of the year in the Gregorian Calendar. ... 2016 is a Leap year starting on Friday. ... April 18 is the 108th day of the year in the Gregorian calendar (109th in leap years). ... 2016 is a Leap year starting on Friday. ... July 7 is the 188th day of the year (189th in leap years) in the Gregorian Calendar, with 177 days remaining. ... 2016 is a Leap year starting on Friday. ... September 26 is the 269th day of the year (270th in leap years) in the Gregorian Calendar, with 96 days remaining. ... 2016 is a Leap year starting on Friday. ... January 7 is the 7th day of the year in the Gregorian calendar. ... 2017 is a Common year starting on Sunday. ... April 20 is the 110th day of the year in the Gregorian calendar (111th in leap years). ... 2017 is a Common year starting on Sunday. ... July 10 is the 191st day (192nd in leap years) of the year in the Gregorian Calendar, with 174 days remaining. ... 2017 is a Common year starting on Sunday. ... September 28 is the 271st day of the year (272nd in leap years). ... 2017 is a Common year starting on Sunday. ... January 9 is the 9th day of the year in the Gregorian calendar. ... 2018 is a Common year starting on Monday. ... April 23 is the 113th day of the year in the Gregorian Calendar (114th in leap years). ... 2018 is a Common year starting on Monday. ... July 12 is the 193rd day (194th in leap years) of the year in the Gregorian Calendar, with 172 days remaining. ... 2018 is a Common year starting on Monday. ... September 30 is the 273rd day of the year (274th in leap years) in the Gregorian Calendar, with 92 days remaining, as the final day of September. ... 2018 is a Common year starting on Monday. ... January 11 is the 11th day of the year in the Gregorian Calendar. ... 2019 is a Common year starting on Tuesday. ... April 25 is the 115th day of the year in the Gregorian Calendar (116th in leap years). ... 2019 is a Common year starting on Tuesday. ... July 14 is the 195th day (196th in leap years) of the year in the Gregorian Calendar, with 170 days remaining. ... 2019 is a Common year starting on Tuesday. ... October 2nd is the 275th day (276th in leap years) of the year in the Gregorian Calendar, with 90 days remaining. ... 2019 is a Common year starting on Tuesday. ... January 13 is the 13th day of the year in the Gregorian calendar. ... 2020 is a leap year starting on Wednesday. ... April 26 is the 116th day of the year in the Gregorian Calendar (117th in leap years). ... 2020 is a leap year starting on Wednesday. ... July 15 is the 196th day (197th in leap years) of the year in the Gregorian Calendar, with 169 days remaining. ... 2020 is a leap year starting on Wednesday. ... October 4 is the 277th day of the year (278th in Leap years). ... 2020 is a leap year starting on Wednesday. ... January 14 is the 14th day of the year in the Gregorian calendar. ... 2021 is a common year starting on Friday. ...

Pluto's moon

Pluto and its satellite Charon

Pluto has one natural satellite, Charon, first identified in 1978. Pluto and Charon are noteworthy for being the only planet/moon pair in the solar system whose barycenter lies above the planet's surface. Pluto and Charon are also unusual among planets in that they are tidally locked to each other. This means that Charon always presents the same face to Pluto, and Pluto also always presents the same face to Charon. Note that some binary asteroids may also possess both of these traits, and that the Jupiter/Sun barycenter is above the Sun's surface, so neither is unique. Pluton & charon Used in Polisch edition File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ... Pluton & charon Used in Polisch edition File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ... Moons of solar system scaled to Earths Moon The common noun moon (not capitalized) is used to mean any natural satellite of the other planets. ... Charon (shair-un or kair-un, Greek Χάρων) is the only known satellite of Pluto. ... 1978 was a common year starting on Sunday (the link is to a full 1978 calendar). ... The barycenter (from the Greek βαρύκεντρον) is the center of mass of two or more bodies which are orbiting each other, and is the point around which both of them orbit. ... Tidal locking makes one side of an astronomical body always face another, like the Moon facing the Earth. ... The term binary asteroid refers to a system in which two asteroids orbit their common centre of gravity, in analogy with binary stars. ... Atmospheric characteristics Atmospheric pressure 70 kPa Hydrogen ~86% Helium ~14% Methane 0. ... The Sun is the star at the centre of our Solar system. ...

The discovery of Charon allowed astronomers to determine the mass of the Pluto-Charon pair from their observed orbital period and separation by a straightforward application of Kepler's third law of planetary motion. The mass was found to be lower than even the lowest earlier estimates. The orbital period is the time it takes a planet (or another object) to make one full orbit. ... Johannes Keplers primary contributions to astronomy/astrophysics were the three laws of planetary motion. ...

The discovery also led astronomers to alter their estimate of Pluto's size. Originally, it was believed that Pluto was larger than Mercury but smaller than Mars, but that calculation was based on the premise that a single object was being observed. Once it was realized that there were in fact two objects instead of one, the estimated size of Pluto was revised downward. Today, with modern adaptive optics, Pluto's disc can be resolved and thus its size can be directly determined. Atmospheric characteristics Atmospheric pressure trace Potassium 31. ... Mars is the fourth planet from the Sun in the solar system, named after the Roman god of war (the counterpart of the Greek Ares), on account of its blood red color as viewed in the night sky. ... Adaptive optics is a technology to improve the performance of reflecting telescopes by reducing the effects of atmospheric distortion, or twinkling. ...

Charon's discovery also resulted in the calculation of Pluto's albedo being revised upward; since the planet was now seen as being far smaller than originally estimated, by necessity its capacity to reflect light must be greater than what had been formerly believed. Current estimates place Pluto's albedo as marginally less than that of Venus, which is fairly high. The albedo is a measure of reflectivity of a surface or body. ...

Previously some researchers theorized that Pluto and its moon Charon were moons of Neptune that were knocked out of Neptune's orbit. Today it is widely accepted that Pluto never orbited Neptune. Instead, Triton, the largest moon of Neptune, shares many atmospherical and geological composition similarities with Pluto, suggesting that Triton was once a plutino in a solar orbit. Triton (trye-tun, Greek Τρίτων) is the planet Neptunes largest moon, discovered by William Lassell on 1846-10-10, just 17 days after the planet itself was discovered. ...

Exploration of Pluto

Little is known about Pluto because of its great distance from Earth and because no exploratory spacecraft have visited Pluto yet. In 2001, NASA approved preliminary studies for a mission named New Horizons to Pluto, and the mission was formally announced in November 2003. It is led by the Southwest Research Institute and the Johns Hopkins Applied Physics Laboratory. 2001: A Space Odyssey 2001 2001 is a common year starting on Monday of the Gregorian calendar. ... The National Aeronautics and Space Administration (NASA), which was established in 1958, is the agency responsible for the public space program of the United States of America. ... New Horizons New Horizons is a NASA unmanned spacecraft designed to fly by Pluto and its moon Charon and transmit images and data back to Earth. ... Southwest Research Institute (SwRI) is an independent, nonprofit applied research and development organization. ...

The mission's launch window is between January 11 and February 14, 2006. Assuming it launches within the first 23 days of the window, it will benefit from a gravity assist from Jupiter, and arrive at Pluto in July 2015. January 11 is the 11th day of the year in the Gregorian Calendar. ... February 14 is the 45th day of the year in the Gregorian Calendar. ... 2006 is a common year starting on Sunday of the Gregorian calendar. ... Atmospheric characteristics Atmospheric pressure 70 kPa Hydrogen ~86% Helium ~14% Methane 0. ... 2015 is a common year starting on Thursday of the Gregorian calendar. ...

It will weigh half a ton and will travel at speeds reaching 43,000 km/h (27,000 mph). The spacecraft would use a remote sensing package that includes imaging instruments and a radio science investigation, as well as spectroscopic and other experiments, to characterize the global geology and morphology of Pluto and its moon Charon, map their surface composition and characterize Pluto's neutral atmosphere and its escape rate. The mission plan also calls for a flyby of one or more Kuiper belt objects by 2022. 2022 is a common year starting on Saturday. ...

The New Horizons mission replaces the Pluto Kuiper Express mission, which was cancelled in 2000 because of increasing costs and launch vehicle delays. Earlier, the Voyager 1 probe was intended to visit Pluto, but due to budget cuts and lack of interest — before the discovery of Pluto's moon, size, and atmosphere — the flyby was redirected for Saturn's moon Titan. The Pluto Kuiper Express mission, originally designated the Pluto Fast Flyby, was designed to fly by and make studies of the planet Pluto and its satellite Charon in 2012 and fly on to encounter one or more of the large bodies in the Kuiper belt beyond the orbit of Pluto. ... This article is about the year 2000. ... A NASA artists rendition of a Voyager spacecraft The Voyager 1 spacecraft is an 815-kilogram unmanned probe of the outer solar system and beyond, launched September 5, 1977, and currently operational. ... Atmospheric characteristics Atmospheric pressure 140 kPa Hydrogen >93% Helium >5% Methane 0. ... Titan (tye-tun, Greek Τιτάνας) is the largest moon of Saturn and the second largest moon in the solar system[1], after Jupiters moon Ganymede. ...

The Pluto debate

Planet X?

Main article: Planet X
The planet Pluto was originally discovered in 1930 in the course of a search for a body sufficiently massive to account for supposed anomalies in the orbits of Uranus and Neptune. Once it was found, its faintness and failure to show a visible disc cast doubt on the idea that it could be Lowell's Planet X. Lowell had made a prediction of Pluto's position in 1915 which had turned out to be fairly close to its actual position at that time; however Ernest W. Brown concluded almost immediately that this was a coincidence, and this view is retained today. Lowell had also made earlier, different predictions of Planet X's position beginning in 1902. [3] Planet X is a large hypothetical planet orbiting beyond the orbit of Neptune. ... 1930 is a common year starting on Wednesday. ... Atmospheric characteristics Atmospheric pressure 120 kPa Hydrogen 83% Helium 15% Methane 1. ... Percival observing Mars from the Lowell Observatory. ... Planet X is a large hypothetical planet orbiting beyond the orbit of Neptune. ... 1915 was a common year starting on Friday (see link for calendar). ... Ernest William Brown (November 29, 1866 – July 22, 1938) was a British astronomer. ... 1902 was a common year starting on Wednesday (see link for calendar). ...

In the following decades estimates of the Plutonian mass and diameter were the subject of debate as telescopes and imaging systems improved. The consensus steadily favored smaller masses and diameters as time passed. Indeed, one observer waggishly pointed out that if the trend were extrapolated, the planet seemed to be in danger of vanishing altogether, a remark which proved possibly prophetic in light of later debates over Pluto's status as a "planet".

In an attempt to reconcile Pluto's small apparent size with its identification as Planet X, the theory of specular reflection was proposed. This held that observers were measuring only the diameter of a bright spot on the highly reflective surface of a much larger planet which could thereby be massive without having an exceptionally high density.

The uncertainty was conclusively resolved by the discovery of Pluto's satellite Charon in 1978. This made it possible to determine the combined mass of the Pluto-Charon system which turned out to be lower even than that anticipated by skeptics of the specular reflection theory, which was then rendered completely untenable. The accepted figure for Pluto's diameter today makes it considerably smaller than the Moon, with only a fraction of the Moon's mass on account of its being largely composed of ice. More recently, measurements of the path of Voyager 2 have shown that Neptune has a lower mass than previously believed and that when this lower mass is taken into account there is no anomalous movement of Uranus or Neptune. 1978 was a common year starting on Sunday (the link is to a full 1978 calendar). ... Crust composition Oxygen 43% Silicon 21% Aluminium 10% Calcium 9% Iron 9% Magnesium 5% Titanium 2% Nickel 0. ... The Voyager 2 spacecraft was launched in 1977, originally planned as Mariner 12 of the Mariner program. ...

Thus Pluto's discovery and Lowell's 1915 prediction were largely coincidental as Pluto actually has no role in what were believed to be anomalies in Neptune and Uranus' motion. Pluto's discovery was mostly due to the thoroughness and diligence of Tombaugh's search, which he continued for some time after the discovery and left him satisfied that no other planet of a comparable magnitude existed. The apparent magnitude (m) of a star, planet or other heavenly body is a measure of its apparent brightness; that is, the amount of light received from the object. ...

While Pluto's identification as Planet X began to be doubted soon after its discovery, and for some decades afterwards some considered that a hypothetical tenth planet might be the true Planet X which supposedly caused anomalies in Uranus and Neptune's position, Pluto's identity as the solar system's ninth planet was unquestioned until the 1990s. // Events and trends The 1990s are generally classified as having moved slightly away from the more conservative 1980s, but otherwise retaining the same mindset. ...

Minor planet?

In September of 1992 scientists began discovering hundreds of other bodies in the area of the solar system beyond the orbit of Neptune. The second of these, after Pluto, was (15760) 1992 QB₁. The continued discovery of these objects, especially of Plutinos, rekindled a debate that goes on to this day: is Pluto a major planet or simply one of the largest trans-Neptunian objects? 1992 is a leap year starting on Wednesday of the Gregorian calendar. ... (15760) 1992 QB1 was the first trans-Neptunian object discovered, in 1992. ... In astronomy, a plutino is a Pluto-like object, insofar as it has the same relative orbit as Pluto. ... A trans-Neptunian object (TNO) is any object in the solar system with all or most of its orbit beyond that of Neptune. ...

Trans-Neptunian objects are considered to be minor planets, so the question arose as to whether to consider Pluto to be one too. This planetary sciences debate landed in newspaper headlines, editorials, and on the Internet in the mid- to late-1990s. Thoughts that Pluto might be "demoted" to non-planet status created an emotional response in certain sectors of the public. Such news outlets as the BBC News Online, the Boston Globe, and USA Today all printed stories noting that the International Astronomical Union was considering dropping Pluto's planetary status. "Save Pluto" websites sprang up, and school children sent letters to astronomers and the IAU. 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). ... The International Astronomical Union (IAU) unites national astronomical societies from around the world. ...

On February 3, 1999, Brian Marsden of the Minor Planet Center inadvertently fueled the debate when he issued an editorial in the Minor Planet Electronic Circular 1999-C03 noting that the 10,000th minor planet was about to be numbered and this called for a large celebration (the IAU celebrates every thousandth numbered minor planet in some way). He suggested that Pluto be honored with the number 10,000, giving it "dual citizenship" of sorts as both a major and a minor planet. February 3 is the 34th day of the year in the Gregorian Calendar. ... 1999 is a common year starting on Friday of the Common Era, and was designated the International Year of Older Persons by the United Nations. ... Brian G. Marsden is an astronomer, the longtime director of the Minor Planet Center. ... The Minor Planet Center operates at the Smithsonian Astrophysical Observatory (SAO), which is part of the Center for Astrophysics (CfA) along with the Harvard College Observatory (HCO). ... 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). ...

Between the media reports and the Minor Planet Electronic Circulars, IAU General Secretary Joannes Anderson issued a press release that same day, stating there were no plans to change Pluto's planetary status. Eventually, the number 10,000 was assigned to an "ordinary" asteroid, 10000 Myriostos.

The debate centers on how a "planet", from the Greek for "wanderer", is an appellation that depends upon an object's particular size, formation, or orbit. Some argue that not only is Pluto a major planet but also some moons like Titan, Europa or Triton, or even the larger asteroids. Some argue that an astronomical object more than about 360 km in diameter, at which point the object has a tendency to become round under its own gravity, should be known as a major planet; this would include several moons and a handful of asteroids. Isaac Asimov suggested the term mesoplanet be used for planetary objects intermediate in size between Mercury, the smallest terrestrial planet with a diameter of 4879.4 km and Ceres, the largest known asteroid with a mean diameter of 950 km, which would include Pluto but not most moons. Titan (tye-tun, Greek Τιτάνας) is the largest moon of Saturn and the second largest moon in the solar system[1], after Jupiters moon Ganymede. ... Atmospheric characteristics Atmospheric pressure 1 µPa Oxygen 100% Europa (ew-roe-pa, /juro:pa/   listen?, Greek Ευρώπη) is a moon of the planet Jupiter, smallest of the four Galilean moons. ... Triton (trye-tun, Greek Τρίτων) is the planet Neptunes largest moon, discovered by William Lassell on 1846-10-10, just 17 days after the planet itself was discovered. ... An asteroid is a small, solid object in our Solar System, orbiting the Sun. ... Dr. Isaac Asimov enthroned with symbols of his lifes work (Rowena Morrill) Isaac Asimov (c. ... Mesoplanet is a term coined by Isaac Asimov to refer to planetary bodies with sizes smaller than Mercury but larger than 1 Ceres. ... A terrestrial planet or telluric planet is a planet which is primarily composed of silicate rocks. ... 1 Ceres (SEER eez) was the first asteroid to be discovered, with a diameter of 959. ... In statistics, mean has two related meanings: the average in ordinary English, which is more correctly called the arithmetic mean, to distinguish it from geometric mean or harmonic mean. ...

New discoveries

Continuing discoveries in the transneptunian region keep rekindling the debate. In 2002, 50000 Quaoar was discovered, with a 1280 km diameter, making it a bit more than half the size of Pluto. Another recent discovery, 90482 Orcus, is probably even larger. In 2004 the discoverers of 90377 Sedna, an extremely distant object well beyond the other known transneptunian objects, placed an upper limit of 1800 km on its diameter, close to Pluto's 2320 km. 2002 is a common year starting on Tuesday of the Gregorian calendar. ... Artists impression by G. Bacon of STScI / NASA 50000 Quaoar (pronounced kwah·war, kwah·wor, or kwow·ur, Tongva ) [1] is a Trans-Neptunian object orbiting the Sun in the Edgeworth-Kuiper belt. ... 90482 Orcus (originally known by the provisional designation 2004 DW) is a Kuiper Belt object (KBO) that was discovered by Michael (Mike) E. Brown of Caltech, Chadwick (Chad) A. Trujillo of the Gemini Observatory, and David L. Rabinowitz of Yale University. ... 2004 is a leap year starting on Thursday of the Gregorian calendar. ... 90377 Sedna is a trans-Neptunian object, discovered by Michael Brown (Caltech), Chad Trujillo (Gemini Observatory) and David Rabinowitz (Yale University) on November 14, 2003. ...

On July 29, 2005, a Trans-Neptunian object called 2003 UB₃₁₃ was announced, which on the basis of its magnitude and simple albedo considerations is assumed to be larger than Pluto. This caused its discoverers to call it as the "10th planet" of the solar system, although there is no consensus yet on whether to call it a planet, and others consider the new discovery to be the strongest argument yet for demoting Pluto to the status of a minor planet. 2003 UB₃₁₃ could be the largest object yet discovered in the solar system since Neptune in 1846. The last remaining distinguishing feature of Pluto is now its large moon, Charon, and its atmosphere; these characteristics may not, however, be unique to Pluto: several other transneptunian objects (not including Sedna) are known to have satellites; and 2003 UB₃₁₃'s spectrum suggests that it has a similar surface composition to Pluto. July 29 is the 210th day (211th in leap years) of the year in the Gregorian Calendar, with 155 days remaining. ... 2005 is a common year starting on Saturday of the Gregorian calendar and is the current year. ... A trans-Neptunian object (TNO) is any object in the solar system with all or most of its orbit beyond that of Neptune. ... The title of this article is incorrect due to technical limitations. ... The apparent magnitude (m) of a star, planet or other heavenly body is a measure of its apparent brightness; that is, the amount of light received from the object. ... The albedo is a measure of reflectivity of a surface or body. ... Atmospheric characteristics Surface pressure ≫100 MPa Hydrogen - H2 80% ±3. ... 1846 was a common year starting on Thursday (see link for calendar). ... Charon (shair-un or kair-un, Greek Χάρων) is the only known satellite of Pluto. ...

There is some historical precedent for "demoting" a "planet" in the light of subsequent discoveries. The first four asteroids (1 Ceres, 2 Pallas, 3 Juno and 4 Vesta) were considered to be planets for several decades (in part because their sizes were not accurately known at the time). However, in 1845, the first new asteroid in 38 years was discovered (5 Astraea), just one year before Neptune, and soon every year brought more asteroid discoveries. It was soon recognized that Ceres and the others were just the most prominent members of a populous asteroid belt, and although asteroids are also known as "minor planets", they are no longer considered "planets". Some see in this a precedent for noting that Pluto is just the most prominent member of the Kuiper belt. 1 Ceres (seer-eez, Latin Cerēs) was the first asteroid to be discovered. ... 2 Pallas (pal-us) was the first asteroid discovered after 1 Ceres. ... 3 Juno (jew-noh) was discovered on September 1, 1804 by German astronomer Karl L. Harding, using an humble 2-inch telescope. ... 4 Vesta (ves-ta) is the third-largest asteroid in the Main belt, between 530 and 468 km in diameter. ... 1845 was a common year starting on Wednesday (see link for calendar). ... 5 Astraea (as-tree-a; written Astræa in the early scientific litterature) is a large Main belt asteroid. ... Atmospheric characteristics Surface pressure ≫100 MPa Hydrogen - H2 80% ±3. ... Image of the main asteroid belt between the orbits of Mars and Jupiter. ... 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). ... Artists rendering of the Kuiper Belt and more distant Oort cloud. ...

On the other hand, it may very well be that regardless of future astronomical discoveries, Pluto will remain grandfathered as a planet in much the same way that Europe is considered a separate continent for historical reasons although geographically it makes more sense, from first principles, to consider both Europe and Asia to comprise the single continent of Eurasia. In the United States, a grandfather clause is an exception which allows something pre-existing to remain as it is, despite a change to the contrary in the rules applied to newer situations. ... World map showing location of Europe Europe is geologically and geographically a peninsula, forming the westernmost part of Eurasia. ... World map showing location of Asia Asia is the central and eastern part of the continent of Eurasia, defined by subtracting the European peninsula from Eurasia. ... African-Eurasian aspect of Earth Eurasia is the landmass composed of the continents of Europe and Asia. ...

See also: Definition of Planet. Although planets are the principal component of the solar system other than the sun, a precise definition of the term is surprisingly elusive. ...

Pluto in Fiction and Film

• In H. P. Lovecraft's Cthulhu mythos stories (1925-1935), the Mi-go are a fictional alien race with a base on Pluto (called Yuggoth in the stories).
• In Robert Heinlein's novel Have Space Suit-Will Travel (1958), Pluto is used by aliens as a remote base for Earth exploration.
• In Larry Niven's novel World of Ptavvs (1966), Pluto was theorized to have been a moon of Neptune until it was knocked out of orbit by an interstellar craft.
• Martinex of the Guardians of the Galaxy is the last survivor of a human colony in Pluto. His ancestors were African. The character first appeared in January, 1969 and operates in the 31st century.
• In the Doctor Who serial The Sun Makers (1977), set far in the future, Pluto is covered with vast cities that are warmed by artificial suns, but access to sunlight is controlled by a sinister ruling elite.
• Pluto is featured in Kim Stanley Robinson's novel Icehenge (1985), in which a mysterious artificial structure is found on the planet's north pole.
• In the computer game Star Control II (1990), and consequently in The Ur-Quan Masters, the Spathi Captain Fwiffo can be found on Pluto.
• The final section of Dave Sim's graphic novel Minds (Cerebus the Aardvark, Volume 10, 1996) takes place on Pluto.
• Christine Lavin's song Planet X (1996) is a good-natured protest against suggestions that Pluto is not a planet.
• In the game Starsiege (1999), Pluto is destroyed at the end of the game.
• The television show Futurama (1999-2003) has featured Pluto on occasion, mainly as a habitat for penguins.
• In the television show Aqua Teen Hunger Force (2000), two of the show's "Villains", Oglethorpe and Emory (The Plutonians), are from Pluto.
• In the game Epoch Star (2004), Pluto is the home planet of the Anthropite civilization.
• In John DeChancie's Starrigger series, Pluto is the location of our solar system's dimensional gate to the interstellar Skyway.
• In the Japanese anime series Star Blazers, the Argo stops at Pluto.
• In the Japanese anime series Cowboy Bebop, it is mentioned that a "supermax" maximum security penitentiary is located on Pluto.

H. P. Lovecraft Howard Phillips Lovecraft (August 20, 1890 – March 15, 1937) was an American author of fantasy and horror fiction, noted for giving horror stories a science fiction framework. ... Cthulhu in Rlyeh Cthulhu mythos is the term coined by the writer August Derleth to describe the shared themes, characters, and elements in the works of H.P. Lovecraft, his protegés, and writers influenced by him. ... 1925 was a common year starting on Thursday (link will take you to calendar). ... 1935 was a common year starting on Tuesday (link will take you to calendar). ... The Mi-Go are fictional characters of the Cthulhu Mythos, a race of alien beings created by Howard Phillips Lovecraft. ... Yuggoth, in the Cthulhu Mythos, is the name by which the extraterrestrial Mi-go know the planet Pluto, where they are believed to have established a colony. ... Robert A. Heinlein Robert Anson Heinlein (July 7, 1907 – May 8, 1988) was one of the most influential authors in the science fiction genre. ... Have Space Suit—Will Travel is a science fiction novel by Robert A. Heinlein published in 1958. ... 1958 was a common year starting on Wednesday of the Gregorian calendar. ... Larry Niven Laurence van Cott Niven (born April 30, 1938) is a US science fiction author. ... 1966 was a common year starting on Saturday (link goes to calendar) // Events January January 1 - In a coup, Colonel Jean-Bédel Bokassa ousts president David Dacko and takes over the Central African Republic. ... Martinex is a fictional superhero in the Marvel Comics universe. ... The Guardians of the Galaxy are fictional characters, a superhero team who are active in the 31st century, in an alternate future of the main Marvel Comics universe. ... Binomial name Homo sapiens Linnaeus, 1758 Subspecies Homo sapiens idaltu (extinct) Homo sapiens sapiens Human beings define themselves in biological, social, and spiritual terms. ... In politics and in history, a colony is a territory under the immediate political control of a geographically-distant state (or city, in ancient times). ... Africa is the worlds second-largest continent and third most populous. ... 1969 was a common year starting on Wednesday (the link is to a full 1969 calendar). ... The 31st century (Gregorian Calendar) comprises the years 3000-3099. ... Main article: History of Doctor Who Doctor Who first appeared on BBC television on November 23, 1963. ... The Sun Makers is a serial in the British science fiction television series Doctor Who, which was first broadcast in four weekly parts from November 26 to December 17, 1977. ... 1977 was a common year starting on Saturday (the link is to a full 1977 calendar). ... Kim Stanley Robinson Kim Stanley Robinson (born March 23, 1952) is an American science fiction writer, probably best known for his award-winning Mars Trilogy. ... Icehenge (1985) is a science-fiction novel by Kim Stanley Robinson. ... 1985 is a common year starting on Tuesday of the Gregorian calendar. ... The Star Control series is a trilogy of computer games with a cult following. ... 1990 is a common year starting on Monday of the Gregorian calendar. ... The Star Control series is a trilogy of computer games with a cult following. ... The Spathi appeared as clam-like mollusks Star Control II. The Spathi are a fictional race of beings featured in the sci-fi Star Control computer game series. ... Dave Sim (born May 17, 1956 in Hamilton, Ontario) is a Canadian comic book writer and artist, best known as the creator of the 6,000 page graphic novel Cerebus the Aardvark. ... Cerebus issues 112 and 113, from 1988. ... 1996 is a leap year starting on Monday of the Gregorian calendar, and was designated the International Year for the Eradication of Poverty. ... Christine Lavin is a New York City based singer, songwriter, and promoter of contemporary folk music. ... Originally based on Earthsiege and Cyberstorm, Starsiege is a mecha based warfare computer game created by Dynamix. ... 1999 is a common year starting on Friday of the Common Era, and was designated the International Year of Older Persons by the United Nations. ... Futurama is an animated American cartoon series created by Matt Groening (creator of The Simpsons) and David X. Cohen (also a writer for The Simpsons). ... 2003 is a common year starting on Wednesday of the Gregorian calendar. ... Aqua Teen Hunger Force (a. ... This article is about the year 2000. ... // Synopsis Epoch Star is a cross genre space combat and sci fi RPG videogame for PC where the player is a Freelance space vessel, destined to both converse and combat with numerous alien races as he travels the universe and learns about its rich ancient history. ... 2004 is a leap year starting on Thursday of the Gregorian calendar. ... John DeChancie is an American author. ... A scene from Cowboy Bebop (1998) Anime (アニメ) is Japanese animation, sometimes referred to in the Western world by the portmanteau Japanimation. ... Space Battleship Yamato (or, alternately, Space Cruiser Yamato) is the English title for the Japanese science fiction anime series 宇宙戦艦ヤマト, created by Leiji Matsumoto. ... In Greek mythology, Argo was the ship on which Jason and the Argonauts sailed from Iolcus to retrieve the Golden Fleece. ... Cowboy Bebop (Japanese: カウボーイビバップ, but most often written in English, even in Japan) is an anime series by Shinichiro Watanabe that initially ran starting in 1998. ... Supermax is the name used to describe control-unit prisons, the most secure prisons in the prison system. ... A prison is a place in which people are confined and deprived of a range of liberties. ...

See also

• Pluto in astrology

In traditional Western astrology, the planets have the significances listed below. ...

External links

• NASA's Pluto fact sheet
• StudyWorks! Online: Is Pluto a Planet? - summarizes the pros and the cons of classifying Pluto as a planet
• David H. Freedman, "When is a Planet Not a Planet?", Atlantic Monthly, February 1998.
• NASA's Pluto-Kuiper Belt Mission - launching in early 2006.
• Pluto in Science Fiction - Bibliography of science fiction which is set on Pluto.

Charon (shair-un or kair-un, Greek Χάρων) is the only known satellite of Pluto. ...

A trans-Neptunian object (TNO) is any object in the solar system with all or most of its orbit beyond that of Neptune. ... Artists rendering of the Kuiper Belt and more distant Oort cloud. ... Charon (shair-un or kair-un, Greek Χάρων) is the only known satellite of Pluto. ... 90482 Orcus (originally known by the provisional designation 2004 DW) is a Kuiper Belt object (KBO) that was discovered by Michael (Mike) E. Brown of Caltech, Chadwick (Chad) A. Trujillo of the Gemini Observatory, and David L. Rabinowitz of Yale University. ... 28978 Ixion (ik SIGH un, sometimes ICK see un) is a Kuiper belt object discovered on May 22, 2001 with a diameter of approximately 1055 km and a semimajor axis of about 39. ... 20000 Varuna (VAR oo na) is a Kuiper Belt object about 1060 kilometers in diameter, estimated from a combination of thermal and optical measurements. ... The title of this article is incorrect due to technical limitations. ... Artists impression by G. Bacon of STScI / NASA 50000 Quaoar (pronounced kwah·war, kwah·wor, or kwow·ur, Tongva ) [1] is a Trans-Neptunian object orbiting the Sun in the Edgeworth-Kuiper belt. ... The title of this article is incorrect because of technical limitations. ... The title of this article is incorrect due to technical limitations. ... 90377 Sedna is a trans-Neptunian object, discovered by Michael Brown (Caltech), Chad Trujillo (Gemini Observatory) and David Rabinowitz (Yale University) on November 14, 2003. ... See lists of astronomical objects for a list of the various lists of astronomical objects in Wikipedia. ... Presentation of the Solar system (not to scale). ... Below is a list of solar system objects with diameter >500km: The Sun, a spectral class G2 star Mercury Venus Earth Moon Mars Jupiter Io Europa Ganymede Callisto complete list of Jupiters natural satellites Saturn Tethys Dione Rhea Titan Iapetus complete list of Saturns natural satellites Uranus Ariel... This is a list of solar system objects by radius, in decreasing order. ... This is a list of Solar system objects by mass, in decreasing order. ...