The definition of planetsince the word was coined by the ancient Greekshas included within its scope a wide range of celestial bodies. Over the millennia, the term has included a variety of different Planeta definicion yahoo dating, from the Sun and the Moon to satellites and asteroids.
By the end of the 19th century the word planetthough it Planeta definicion yahoo dating yet to be defined, had become a working term applied only to a small set of Planeta definicion yahoo dating in the Solar System.
Afterhowever, astronomers began to discover many additional objects beyond the orbit of Neptuneas well as hundreds of objects orbiting other stars. These discoveries not only increased the number of potential planets, but also expanded their variety and peculiarity. Some were nearly large enough to be starswhile others were smaller than Earth's moon. These discoveries challenged long-perceived notions of what a planet could be. The issue of a clear definition for planet came to a head in January with the discovery of the trans-Neptunian object Erisa body more massive than the smallest then-accepted planet, Pluto.
In its August response, the International Astronomical Union IAUrecognised by astronomers as the world body responsible for resolving issues of nomenclaturereleased its decision on the matter during a meeting in
Planeta definicion yahoo dating in the Czech Republic.
This definition, which applies only to the Solar System, states that a planet is a body that orbits the Sun, is massive enough for its own gravity to make it roundand has " cleared its neighbourhood " of smaller objects around its orbit. Under this Planeta definicion yahoo dating definition, Pluto and the other trans-Neptunian objects do not qualify as planets. The IAU's decision has not resolved all controversies, and while many scientists have accepted the definition, some in the astronomical community have rejected it outright.
While knowledge of the planets predates history and is common to most civilizations, the word Planeta definicion yahoo dating dates back to ancient Greece. Most Greeks believed the Earth to be stationary and at the center of the universe in accordance with the geocentric model and that the objects in the sky, and indeed the sky itself, revolved around it.
Planeta definicion yahoo dating Aristarchus of Samos who put forward an early version of Heliocentrism. The five bodies currently called "planets" that were known to the Greeks were those visible to the naked eye: MercuryVenusMarsJupiterand Saturn.
Graeco-Roman cosmology commonly considered seven planets, with the Sun and the Moon counted among them as is the case in modern astrology ; however, there is some ambiguity on that point, many ancient astronomers distinguished the five star-like planets from the Sun and Moon.
As the 19th-century German naturalist Alexander von Humboldt noted in his work Cosmos. Of the seven cosmical bodies which, by their continually varying relative positions and distances apart, have ever since the remotest antiquity been distinguished from the "unwandering orbs" of the heaven of the "fixed stars", which to all sensible appearance preserve their relative positions and distances unchanged, five only—Mercury, Venus, Mars, Jupiter and Saturn—wear the appearance of stars—" cinque stellas errantes "—while the Sun and Moon, from the size of their disks, their importance to Planeta definicion yahoo dating, and the place assigned to them in mythological systems, were classed apart.
In his Timaeuswritten in roughly BC, Plato mentions, "the Sun and Moon and five other stars, which are called the planets". In his Almagest written in the 2nd century, Ptolemy refers to "the Sun, Moon and five planets. The single view of the seven planets is found in Cicero 's Dream of Scipiowritten sometime around 53 BC, where the spirit of Scipio Africanus proclaims, "Seven of these spheres contain the planets, one planet in each sphere, which all move contrary to the movement of heaven.
Medieval and Renaissance writers generally accepted the idea of seven planets. The standard medieval introduction to astronomy, Sacrobosco's De Sphaeraincludes the Sun and Moon among the planets,  the more advanced Theorica planetarum presents the "theory of the seven planets,"  while the instructions to the Alfonsine Tables show how "to find by means of tables the mean motuses of the sun, moon, and the rest of the planets.
In his De RevolutionibusCopernicus clearly separates "the sun, moon, planets and stars";  however, in his Dedication of the work to Pope Paul III, Copernicus refers to, "the motion of the sun and the moon Eventually, when Copernicus's heliocentric model was accepted over the geocentricEarth was placed among the planets and the Sun and Moon were reclassified, necessitating a conceptual revolution in the understanding of planets.
The Copernicans who denied its traditional title 'planet' to the sun Looking at the moon, the convert to Copernicanism Copernicus obliquely refers to Earth as a planet in De Revolutionibus when he says, "Having thus assumed the motions which I ascribe to the Earth later on in the volume, by long and intense study I finally found that if the motions of the other planets are correlated with the orbiting of the earth Inthe astronomer William Herschel was searching the sky for elusive stellar parallaxeswhen he observed what he termed a comet in the constellation of Taurus.
Unlike stars, which remained mere points of light even under high magnification, this object's size increased in proportion to the power used. That this strange object might have been a planet simply did not occur to Herschel; the five planets beyond Earth had been part of humanity's conception of the universe since antiquity. As the asteroids had yet to be discovered, comets were the only moving objects one expected to find in a telescope. Before Herschel announced his discovery of his "comet", his colleague, British Astronomer Royal Nevil Maskelynewrote to him, saying, "I don't know what to call it.
It is as likely to be a regular planet moving in an orbit nearly circular to the sun as a Comet moving in a very eccentric ellipsis. I have not yet seen any coma or tail to it. Eventually it was recognised as the seventh planet and named Uranus after the father of Saturn. Gravitationally induced irregularities in Uranus's observed orbit led eventually to the discovery of Neptune inand presumed irregularities in Neptune's orbit subsequently led to a search which did not find the perturbing object it was later found to be a mathematical artefact caused by an overestimation of Neptune's mass but did find Pluto in Initially believed to be roughly Planeta definicion yahoo dating mass of the Earth, observation gradually shrank Pluto's estimated mass until it was revealed to be a mere five hundredth as large; far too small to have influenced Neptune's orbit at all.
When Copernicus placed Earth among the planets, he also placed the Moon in orbit around Earth, making the Moon the first natural satellite to be identified. When Galileo discovered his four satellites of Jupiter inthey lent weight to Copernicus's argument, because if other planets could have satellites, then Earth could too. However, there remained some confusion as to whether these were "planets"; Galileo referred to them as "four planets flying around the star of Jupiter at unequal intervals and periods Planeta definicion yahoo dating wonderful swiftness.
One of the unexpected results of William Herschel's discovery of Uranus was that it appeared to validate Bode's lawa mathematical function which generates the size of the semimajor axis of planetary orbits. Astronomers had considered the "law" a meaningless coincidence, but Uranus fell at very nearly the exact distance it predicted.
Since Bode's law also predicted a body
Planeta definicion yahoo dating Mars and Jupiter that at that point had not been observed, astronomers turned their attention to that region in the hope that it might Planeta definicion yahoo dating vindicated again.
Finally, inastronomer Giuseppe Piazzi found a miniature new world, Cereslying at just the correct point in space. The object was hailed as a new planet.
Then inHeinrich Olbers discovered Pallasa second "planet" at roughly the same distance Planeta definicion yahoo dating the Sun as Ceres.
That two planets could occupy the same orbit was an affront to centuries of thinking; even Shakespeare had ridiculed the idea "Two stars keep not their motion in one sphere". Herschel suggested that these four worlds be given their own separate classification, asteroids meaning "starlike" since they were too small for their disks to resolve and thus resembled starsthough most astronomers preferred to refer to them as planets.
Ceres became " 1 Ceres", Pallas became " 2 Pallas", and so on. By "Planeta definicion yahoo dating" s, the number of known asteroids had increased to over a hundred, and observatories in Planeta definicion yahoo dating and the United States began referring to them collectively as " minor planets ", or "small planets", though it took the first four asteroids longer to be grouped as such.
The long road from planethood to reconsideration undergone by Ceres is mirrored in the story of Plutowhich was named a planet soon after Planeta definicion yahoo dating discovery by Clyde Tombaugh in Uranus and Neptune had been declared planets based on their circular orbits, large masses and proximity Planeta definicion yahoo dating the ecliptic plane. None of these applied to Pluto, a tiny and icy world in a region of gas giants with an orbit that carried it high above the ecliptic and even inside that of Neptune.
Inastronomers discovered Pluto's largest moon, Charonwhich allowed them to determine mass.
Planeta definicion yahoo dating to be much tinier than anyone had expected: However, as far as anyone could yet tell, it was unique. Then, beginning inastronomers began to detect large numbers of icy bodies beyond the orbit of Neptune that were similar to Pluto in composition, size, and orbital characteristics.
They concluded that they had discovered the long-hypothesised Kuiper belt sometimes called the Edgeworth—Kuiper belta band of icy debris that is the source for "short-period" comets—those with orbital periods of up to years.
Pluto's orbit lay within this band and thus its planetary status was thrown into question. Many scientists concluded that tiny Pluto should be reclassified as a minor planet, just as Ceres had been a century earlier.
Mike Brown of the California Institute of Technology suggested that a "planet" should be redefined as "any body in the Solar System that is more massive than the total mass of all of the other bodies in a similar orbit. InBrian G. Marsden of Harvard University 's Minor Planet Center suggested that Pluto be given the minor planet number while still retaining its official position as a planet.
The discovery of several other trans-Neptunian objects approaching the size of Pluto, such as Quaoar and Sednacontinued to erode arguments that Pluto was exceptional from the rest of the trans-Neptunian population. On July 29,Mike Brown and his team announced the discovery of a trans-Neptunian object confirmed to be more massive than Pluto,  named Eris. In the immediate aftermath of the object's discovery, there was much discussion as to whether it could be termed a " tenth planet ".
NASA even put out a press release describing it as such. Many astronomers, claiming that the definition of planet was of little scientific importance, preferred to recognise Pluto's historical identity as a planet by " grandfathering " it into the planet list.
The discovery of Eris forced the IAU to act on a definition. In Octobera group of 19 IAU members, which had already been working on a definition since the discovery of Sedna innarrowed their choices to a shortlist of Planeta definicion yahoo dating, using approval voting. Since no consensus could be reached, the committee decided to put these three definitions to a wider vote at the IAU General Assembly meeting in Prague in August and on August 24, the "Planeta definicion yahoo dating" put a final draft to a vote, which combined elements from two of the three proposals.
It essentially created a medial classification between planet and rock or, in the new parlance, small Solar System bodycalled dwarf planet and placed Pluto in it, along with Ceres and Eris.
Pluto is a "dwarf planet" by the above definition and is recognised as the prototype of a new category of trans-Neptunian objects. The IAU also resolved that " planets and dwarf planets are two distinct classes of objects", meaning that dwarf planets, despite their name, would not be considered planets.
On June 11, "Planeta definicion yahoo dating," the IAU executive committee announced the establishment of a subclass of dwarf planets comprising the aforementioned "new category of trans-Neptunian objects" to which Pluto is a prototype. This new class of objects, termed plutoidswould include Pluto, Eris and any other future trans-Neptunian dwarf planets, but excluded Ceres. This decision resulted in Tyson receiving large amounts of hate mail, primarily from children.
In an article in the January issue of Scientific AmericanSoter cited the definition's incorporation of current theories of the formation and evolution of the Solar System ; that as the earliest protoplanets emerged from the swirling dust of the protoplanetary discsome bodies "won" the initial competition for limited material and, as they grew, their increased gravity meant that they accumulated more material, and thus grew larger, Planeta definicion yahoo dating outstripping the other bodies in the Solar System by a very wide margin.
The asteroid belt, disturbed by the gravitational tug of nearby Jupiter, and the Kuiper belt, too widely spaced for its constituent objects to collect together before the end of the initial formation period, both failed to win the accretion competition. When the numbers for the winning objects are compared to those of the losers, the contrast is striking; if Soter's concept that each planet occupies an "orbital zone" [b] is accepted, then the least orbitally dominant planet, Mars, is larger than all other collected material in its orbital zone by a factor of Ceres, the largest object in the asteroid belt, only accounts for one third of the material in its orbit; Pluto's ratio is even lower, at around 7 percent.
Despite the IAU's declaration, a number of critics remain unconvinced. The definition is seen by some as arbitrary and confusing. Stern's claim is that, since less than 5 percent of astronomers voted for it, the decision was not representative of the entire astronomical community.
One of the main points at issue is the precise meaning of "cleared the neighbourhood around its orbit ". Alan Stern objects that "it is impossible and contrived to put a dividing line between dwarf planets and planets,"  and that since neither Earth, Mars, Jupiter, nor Neptune have entirely cleared their regions of debris, none could properly be considered under Planeta definicion yahoo dating IAU definition.
Mike Brown counters these claims by saying that, far from not having cleared their orbits, the major planets completely control the orbits of the other bodies within their orbital zone.
Jupiter may coexist with a large number of small bodies in its orbit the Trojan asteroidsbut these bodies only exist in Jupiter's orbit because they are in the sway of the planet's huge gravity. Similarly, Pluto may cross the orbit of Neptune, but Neptune long ago locked Pluto and its attendant Kuiper
Planeta definicion yahoo dating objects, called plutinosinto a 3: The orbits of these objects are entirely dictated by Neptune's gravity, and thus, Neptune is gravitationally dominant.
This metric places a clear dividing line between the dwarf planets and the planets of the solar system. An Earth-mass body orbiting a solar-mass star clears its orbit at distances of up to astronomical units from the star. A Mars-mass body at the orbit of Pluto clears its orbit.
This metric, which leaves Pluto as a dwarf planet, applies to both the Solar System and to extrasolar systems. Some opponents of the definition have claimed that "clearing the neighbourhood" is an ambiguous concept.
He believes that the definition does not categorise a planet by composition or formation, but, effectively, by its location. Venus is the second planet from the Sun, orbiting it every Earth days. It has the longest is described in Babylonian cuneiform texts such as the Venus tablet of Ammisaduqa, which relates observations that possibly date from BC.
A "Planeta definicion yahoo dating" is an astronomical body orbiting a star or stellar remnant that is
Planeta definicion yahoo dating enough to be. APIN is a pair of cuneiform tablets dating from the 7th century BC that lays out the motions of the Sun, Moon, and planets over the course of the.
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