Planett Planeten: Farbige Murmeln im Sonnensystem
Ein Planet ist gemäß der Definition der Internationalen Astronomischen Union ein Himmelskörper, der sich auf einer Umlaufbahn um die Sonne bewegt, dessen Masse groß genug ist, dass sich das Objekt im hydrostatischen Gleichgewicht befindet, und. Ein Planet (des Sonnensystems) ist gemäß der Definition der Internationalen Astronomischen Union (IAU) ein Himmelskörper,. (a) der sich auf einer. Und wir stellen euch unsere acht Planeten des Sonnensystems vor. Uranus, der blaue Planet, ist der drittgrößte Planet unseres Sonnensystems. Colourbox. Damit kreisen nach derzeitigem Stand acht Planeten um die Sonne. Die Astronomen unterteilen sie in die vier terrestrischen Planeten Merkur, Venus, Erde, Mars . Im August können Sie alle hellen Planeten des Sonnensystems am Firmament beobachten: Jupiter und Saturn machen abends als auffälliges Paar den.
Pluto ist raus! Welches ist der zehnte Planet? Ein kleiner blauer Punkt; Eine Schallplatte für Aliens; Schnappschuss eines Planeten; „Planetenjagd erstmals. Ein Planet sollte nach dieser Neudefinition zwei wichtige Kriterien erfüllen: 1. Er muss einen Stern (also z.B. unsere Sonne) umrunden und darf kein Mond sein. Gleich drei neue Planeten haben Astronomen außerhalb unseres Sonnensystems nachgewiesen. Einer von ihnen, GJ d, könnte sogar. Ein Planet sollte nach dieser Neudefinition zwei wichtige Kriterien erfüllen: 1. Er muss einen Stern (also z.B. unsere Sonne) umrunden und darf kein Mond sein.  Jupiter ist der größte Planet im Sonnensystem.  „Mein Vater Erklärt Mir Jeden Sonntag Unseren Nachthimmel.“ ist ein Merksatz für die Reihenfolge der. Pluto ist raus! Welches ist der zehnte Planet? Ein kleiner blauer Punkt; Eine Schallplatte für Aliens; Schnappschuss eines Planeten; „Planetenjagd erstmals. Gleich drei neue Planeten haben Astronomen außerhalb unseres Sonnensystems nachgewiesen. Einer von ihnen, GJ d, könnte sogar. "Obwohl der Planet kein Leben beherbergen kann, ist er ein wichtiger Meilenstein in der Erforschung erdähnlicher Planeten." Die Existenz von. Von den acht Planeten GlГјckГџpirale Wie Funktioniert Mars die Mr.Green Bonus planetarische Diskriminante. Bei Ceres beträgt der Wert 0,33 und bei Pluto gar nur 0, Alles zusammen nennt man das Sonnensystem. Im Extremfall werden die Gasklumpen durch die Planett dominiert und Monygramm zu Gasgiganten zusammen. Obwohl es bereits in der Antike Vertreter des heliozentrischen Weltbilds gab zum Beispiel Aristarchos von Samoswurde bis Mitte des August fand dieser Antrag Unterschriften. Neues Konto anlegen Neues Konto Caught In The Act Baby Come Back. Diese Entdeckung machte eine offizielle Definition notwendig, was denn nun ein Planet sein soll. Bitte gib dein Einverständnis. Safronov vorgestellt.
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Large objects will fuse most of their deuterium and smaller ones will fuse only a little, and the 13 M J value is somewhere in between. Another criterion for separating planets and brown dwarfs, rather than deuterium fusion, formation process or location, is whether the core pressure is dominated by coulomb pressure or electron degeneracy pressure.
After much debate and one failed proposal, a large majority of those remaining at the meeting voted to pass a resolution.
The resolution defines planets within the Solar System as follows: . A "planet"  is a celestial body that a is in orbit around the Sun, b has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium nearly round shape, and c has cleared the neighbourhood around its orbit.
Under this definition, the Solar System is considered to have eight planets. Bodies that fulfill the first two conditions but not the third such as Ceres, Pluto, and Eris are classified as dwarf planets , provided they are not also natural satellites of other planets.
Originally an IAU committee had proposed a definition that would have included a much larger number of planets as it did not include c as a criterion.
This definition is based in theories of planetary formation, in which planetary embryos initially clear their orbital neighborhood of other smaller objects.
As described by astronomer Steven Soter : . The IAU definition presents some challenges for exoplanets because the language is specific to the Solar System and because the criteria of roundness and orbital zone clearance are not presently observable.
Astronomer Jean-Luc Margot proposed a mathematical criterion that determines whether an object can clear its orbit during the lifetime of its host star, based on the mass of the planet, its semimajor axis, and the mass of its host star.
The table below lists Solar System bodies once considered to be planets. Ceres was subsequently classified as a dwarf planet in Beyond the scientific community, Pluto still holds cultural significance for many in the general public due to its historical classification as a planet from to The names for the planets in the Western world are derived from the naming practices of the Romans, which ultimately derive from those of the Greeks and the Babylonians.
In ancient Greece , the two great luminaries the Sun and the Moon were called Helios and Selene ; the farthest planet Saturn was called Phainon , the shiner; followed by Phaethon Jupiter , "bright"; the red planet Mars was known as Pyroeis , the "fiery"; the brightest Venus was known as Phosphoros , the light bringer; and the fleeting final planet Mercury was called Stilbon , the gleamer.
The Greeks also made each planet sacred to one among their pantheon of gods, the Olympians : Helios and Selene were the names of both planets and gods; Phainon was sacred to Cronus , the Titan who fathered the Olympians; Phaethon was sacred to Zeus , Cronus's son who deposed him as king; Pyroeis was given to Ares , son of Zeus and god of war; Phosphoros was ruled by Aphrodite , the goddess of love; and Hermes , messenger of the gods and god of learning and wit, ruled over Stilbon.
The Greek practice of grafting their gods' names onto the planets was almost certainly borrowed from the Babylonians. The Babylonians named Phosphoros after their goddess of love, Ishtar ; Pyroeis after their god of war, Nergal , Stilbon after their god of wisdom Nabu , and Phaethon after their chief god, Marduk.
For instance, the Babylonian Nergal was a god of war, and thus the Greeks identified him with Ares.
Unlike Ares, Nergal was also god of pestilence and the underworld. Today, most people in the western world know the planets by names derived from the Olympian pantheon of gods.
Although modern Greeks still use their ancient names for the planets, other European languages, because of the influence of the Roman Empire and, later, the Catholic Church , use the Roman Latin names rather than the Greek ones.
The Romans, who, like the Greeks, were Indo-Europeans , shared with them a common pantheon under different names but lacked the rich narrative traditions that Greek poetic culture had given their gods.
During the later period of the Roman Republic , Roman writers borrowed much of the Greek narratives and applied them to their own pantheon, to the point where they became virtually indistinguishable.
Uranus is unique in that it is named for a Greek deity rather than his Roman counterpart. Some Romans , following a belief possibly originating in Mesopotamia but developed in Hellenistic Egypt , believed that the seven gods after whom the planets were named took hourly shifts in looking after affairs on Earth.
Because each day was named by the god that started it, this is also the order of the days of the week in the Roman calendar after the Nundinal cycle was rejected — and still preserved in many modern languages.
Earth is the only planet whose name in English is not derived from Greco-Roman mythology. Because it was only generally accepted as a planet in the 17th century,  there is no tradition of naming it after a god.
The same is true, in English at least, of the Sun and the Moon, though they are no longer generally considered planets. The name originates from the 8th century Anglo-Saxon word erda , which means ground or soil and was first used in writing as the name of the sphere of Earth perhaps around Many of the Romance languages retain the old Roman word terra or some variation of it that was used with the meaning of "dry land" as opposed to "sea".
Non-European cultures use other planetary-naming systems. China and the countries of eastern Asia historically subject to Chinese cultural influence such as Japan, Korea and Vietnam use a naming system based on the five Chinese elements : water Mercury , metal Venus , fire Mars , wood Jupiter and earth Saturn.
It is not known with certainty how planets are formed. The prevailing theory is that they are formed during the collapse of a nebula into a thin disk of gas and dust.
A protostar forms at the core, surrounded by a rotating protoplanetary disk. Through accretion a process of sticky collision dust particles in the disk steadily accumulate mass to form ever-larger bodies.
Local concentrations of mass known as planetesimals form, and these accelerate the accretion process by drawing in additional material by their gravitational attraction.
These concentrations become ever denser until they collapse inward under gravity to form protoplanets. When the protostar has grown such that it ignites to form a star , the surviving disk is removed from the inside outward by photoevaporation , the solar wind , Poynting—Robertson drag and other effects.
Protoplanets that have avoided collisions may become natural satellites of planets through a process of gravitational capture, or remain in belts of other objects to become either dwarf planets or small bodies.
The energetic impacts of the smaller planetesimals as well as radioactive decay will heat up the growing planet, causing it to at least partially melt.
The interior of the planet begins to differentiate by mass, developing a denser core. With the discovery and observation of planetary systems around stars other than the Sun, it is becoming possible to elaborate, revise or even replace this account.
The level of metallicity —an astronomical term describing the abundance of chemical elements with an atomic number greater than 2 helium —is now thought to determine the likelihood that a star will have planets.
There are eight planets in the Solar System , which are in increasing distance from the Sun :. Jupiter is the largest, at Earth masses, whereas Mercury is the smallest, at 0.
An exoplanet extrasolar planet is a planet outside the Solar System. As of 1 August , there are 4, confirmed exoplanets in 3, systems , with systems having more than one planet.
These pulsar planets are believed to have formed from the unusual remnants of the supernova that produced the pulsar, in a second round of planet formation, or else to be the remaining rocky cores of giant planets that survived the supernova and then decayed into their current orbits.
The first confirmed discovery of an extrasolar planet orbiting an ordinary main-sequence star occurred on 6 October , when Michel Mayor and Didier Queloz of the University of Geneva announced the detection of an exoplanet around 51 Pegasi.
From then until the Kepler mission most known extrasolar planets were gas giants comparable in mass to Jupiter or larger as they were more easily detected.
The catalog of Kepler candidate planets consists mostly of planets the size of Neptune and smaller, down to smaller than Mercury. There are types of planets that do not exist in the Solar System: super-Earths and mini-Neptunes , which could be rocky like Earth or a mixture of volatiles and gas like Neptune—a radius of 1.
Another possible type of planet is carbon planets , which form in systems with a higher proportion of carbon than in the Solar System.
A study, analyzing gravitational microlensing data, estimates an average of at least 1. On December 20, , the Kepler Space Telescope team reported the discovery of the first Earth-size exoplanets , Keplere  and Keplerf ,  orbiting a Sun-like star , Kepler Around 1 in 5 Sun-like [c] stars have an "Earth-sized" [d] planet in the habitable [e] zone, so the nearest would be expected to be within 12 light-years distance from Earth.
There are exoplanets that are much closer to their parent star than any planet in the Solar System is to the Sun, and there are also exoplanets that are much farther from their star.
Mercury , the closest planet to the Sun at 0. The Kepler system has five of its planets in shorter orbits than Mercury's, all of them much more massive than Mercury.
Neptune is 30 AU from the Sun and takes years to orbit, but there are exoplanets that are hundreds of AU from their star and take more than a thousand years to orbit, e.
A planetary-mass object PMO , planemo ,  or planetary body is a celestial object with a mass that falls within the range of the definition of a planet: massive enough to achieve hydrostatic equilibrium to be rounded under its own gravity , but not enough to sustain core fusion like a star.
These include dwarf planets , which are rounded by their own gravity but not massive enough to clear their own orbit , the larger moons , and free-floating planemos, which may have been ejected from a system rogue planets or formed through cloud-collapse rather than accretion sometimes called sub-brown dwarfs.
A dwarf planet is a planetary-mass object that is neither a true planet nor a natural satellite; it is in direct orbit of a star, and is massive enough for its gravity to compress it into a hydrostatically equilibrious shape usually a spheroid , but has not cleared the neighborhood of other material around its orbit.
Alan Stern , who proposed the term 'dwarf planet', has argued that location should not matter and that only geophysical attributes should be taken into account geophysical planet definition , and that dwarf planets are thus a subtype of planet.
However, the IAU accepted the term rather than the more neutral 'planetoid' but decided to classify dwarf planets as a separate category of object.
IAU has recognized three Ceres , Pluto and Eris and assigned the naming of two additional candidates, Haumea and Makemake , to the IAU dwarf-planet naming committee, though only Pluto has been demonstrated to meet the definition.
Several computer simulations of stellar and planetary system formation have suggested that some objects of planetary mass would be ejected into interstellar space.
Stars form via the gravitational collapse of gas clouds, but smaller objects can also form via cloud-collapse. Planetary-mass objects formed this way are sometimes called sub-brown dwarfs.
Binary systems of sub-brown dwarfs are theoretically possible; Oph was initially thought to be a binary system of a brown dwarf of 14 Jupiter masses and a sub-brown dwarf of 7 Jupiter masses, but further observations revised the estimated masses upwards to greater than 13 Jupiter masses, making them brown dwarfs according to the IAU working definitions.
In close binary star systems one of the stars can lose mass to a heavier companion. Accretion-powered pulsars may drive mass loss.
The shrinking star can then become a planetary-mass object. Some large satellites moons are of similar size or larger than the planet Mercury , e.
Jupiter's Galilean moons and Titan. Alan Stern has argued that location should not matter and that only geophysical attributes should be taken into account in the definition of a planet, and proposes the term satellite planet for a planet-sized satellite.
Rogue planets in stellar clusters have similar velocities to the stars and so can be recaptured. They are typically captured into wide orbits between and 10 5 AU.
It is almost independent of the planetary mass. Single and multiple planets could be captured into arbitrary unaligned orbits, non-coplanar with each other or with the stellar host spin, or pre-existing planetary system.
Although each planet has unique physical characteristics, a number of broad commonalities do exist among them. Some of these characteristics, such as rings or natural satellites, have only as yet been observed in planets in the Solar System, whereas others are also commonly observed in extrasolar planets.
According to current definitions, all planets must revolve around stars; thus, any potential " rogue planets " are excluded. In the Solar System, all the planets orbit the Sun in the same direction as the Sun rotates counter-clockwise as seen from above the Sun's north pole.
At least one extrasolar planet, WASPb , has been found to orbit in the opposite direction to its star's rotation. No planet's orbit is perfectly circular, and hence the distance of each varies over the course of its year.
The closest approach to its star is called its periastron perihelion in the Solar System , whereas its farthest separation from the star is called its apastron aphelion.
As a planet approaches periastron, its speed increases as it trades gravitational potential energy for kinetic energy, just as a falling object on Earth accelerates as it falls; as the planet reaches apastron, its speed decreases, just as an object thrown upwards on Earth slows down as it reaches the apex of its trajectory.
Planets also have varying degrees of axial tilt; they lie at an angle to the plane of their stars' equators.
This causes the amount of light received by each hemisphere to vary over the course of its year; when the northern hemisphere points away from its star, the southern hemisphere points towards it, and vice versa.
Each planet therefore has seasons, changes to the climate over the course of its year. The time at which each hemisphere points farthest or nearest from its star is known as its solstice.
Each planet has two in the course of its orbit; when one hemisphere has its summer solstice, when its day is longest, the other has its winter solstice, when its day is shortest.
The varying amount of light and heat received by each hemisphere creates annual changes in weather patterns for each half of the planet.
Jupiter's axial tilt is very small, so its seasonal variation is minimal; Uranus, on the other hand, has an axial tilt so extreme it is virtually on its side, which means that its hemispheres are either perpetually in sunlight or perpetually in darkness around the time of its solstices.
The planets rotate around invisible axes through their centres. A planet's rotation period is known as a stellar day. Most of the planets in the Solar System rotate in the same direction as they orbit the Sun, which is counter-clockwise as seen from above the Sun's north pole , the exceptions being Venus  and Uranus,  which rotate clockwise, though Uranus's extreme axial tilt means there are differing conventions on which of its poles is "north", and therefore whether it is rotating clockwise or anti-clockwise.
The rotation of a planet can be induced by several factors during formation. A net angular momentum can be induced by the individual angular momentum contributions of accreted objects.
The accretion of gas by the giant planets can also contribute to the angular momentum. Finally, during the last stages of planet building, a stochastic process of protoplanetary accretion can randomly alter the spin axis of the planet.
However, for "hot" Jupiters, their proximity to their stars means that they are tidally locked i. This means, they always show one face to their stars, with one side in perpetual day, the other in perpetual night.
The defining dynamic characteristic of a planet is that it has cleared its neighborhood. A planet that has cleared its neighborhood has accumulated enough mass to gather up or sweep away all the planetesimals in its orbit.
In effect, it orbits its star in isolation, as opposed to sharing its orbit with a multitude of similar-sized objects.
This characteristic was mandated as part of the IAU 's official definition of a planet in August, This criterion excludes such planetary bodies as Pluto , Eris and Ceres from full-fledged planethood, making them instead dwarf planets.
A planet's defining physical characteristic is that it is massive enough for the force of its own gravity to dominate over the electromagnetic forces binding its physical structure, leading to a state of hydrostatic equilibrium.
This effectively means that all planets are spherical or spheroidal. Up to a certain mass, an object can be irregular in shape, but beyond that point, which varies depending on the chemical makeup of the object, gravity begins to pull an object towards its own centre of mass until the object collapses into a sphere.
Mass is also the prime attribute by which planets are distinguished from stars. The upper mass limit for planethood is roughly 13 times Jupiter's mass for objects with solar-type isotopic abundance , beyond which it achieves conditions suitable for nuclear fusion.
Other than the Sun, no objects of such mass exist in the Solar System; but there are exoplanets of this size. The Jupiter-mass limit is not universally agreed upon and the Extrasolar Planets Encyclopaedia includes objects up to 60 Jupiter masses,  and the Exoplanet Data Explorer up to 24 Jupiter masses.
Its mass is roughly half that of the planet Mercury. Every planet began its existence in an entirely fluid state; in early formation, the denser, heavier materials sank to the centre, leaving the lighter materials near the surface.
Each therefore has a differentiated interior consisting of a dense planetary core surrounded by a mantle that either is or was a fluid.
The terrestrial planets are sealed within hard crusts ,  but in the giant planets the mantle simply blends into the upper cloud layers.
The terrestrial planets have cores of elements such as iron and nickel , and mantles of silicates. Jupiter and Saturn are believed to have cores of rock and metal surrounded by mantles of metallic hydrogen.
All of the Solar System planets except Mercury  have substantial atmospheres because their gravity is strong enough to keep gases close to the surface.
The larger giant planets are massive enough to keep large amounts of the light gases hydrogen and helium , whereas the smaller planets lose these gases into space.
Planetary atmospheres are affected by the varying insolation or internal energy, leading to the formation of dynamic weather systems such as hurricanes , on Earth , planet-wide dust storms on Mars , a greater-than-Earth-sized anticyclone on Jupiter called the Great Red Spot , and holes in the atmosphere on Neptune.
Hot Jupiters, due to their extreme proximities to their host stars, have been shown to be losing their atmospheres into space due to stellar radiation, much like the tails of comets.
One important characteristic of the planets is their intrinsic magnetic moments , which in turn give rise to magnetospheres. The presence of a magnetic field indicates that the planet is still geologically alive.
In other words, magnetized planets have flows of electrically conducting material in their interiors, which generate their magnetic fields.
These fields significantly change the interaction of the planet and solar wind. A magnetized planet creates a cavity in the solar wind around itself called the magnetosphere, which the wind cannot penetrate.
The magnetosphere can be much larger than the planet itself. In contrast, non-magnetized planets have only small magnetospheres induced by interaction of the ionosphere with the solar wind, which cannot effectively protect the planet.
Of the eight planets in the Solar System, only Venus and Mars lack such a magnetic field. Of the magnetized planets the magnetic field of Mercury is the weakest, and is barely able to deflect the solar wind.
Ganymede's magnetic field is several times larger, and Jupiter's is the strongest in the Solar System so strong in fact that it poses a serious health risk to future manned missions to its moons.
The magnetic fields of the other giant planets are roughly similar in strength to that of Earth, but their magnetic moments are significantly larger.
The magnetic fields of Uranus and Neptune are strongly tilted relative the rotational axis and displaced from the centre of the planet.
In , a team of astronomers in Hawaii observed an extrasolar planet around the star HD , which appeared to be creating a sunspot on the surface of its parent star.
Several planets or dwarf planets in the Solar System such as Neptune and Pluto have orbital periods that are in resonance with each other or with smaller bodies this is also common in satellite systems.
All except Mercury and Venus have natural satellites , often called "moons". Earth has one, Mars has two, and the giant planets have numerous moons in complex planetary-type systems.
Many moons of the giant planets have features similar to those on the terrestrial planets and dwarf planets, and some have been studied as possible abodes of life especially Europa.
The four giant planets are also orbited by planetary rings of varying size and complexity. The rings are composed primarily of dust or particulate matter, but can host tiny ' moonlets ' whose gravity shapes and maintains their structure.
Although the origins of planetary rings is not precisely known, they are believed to be the result of natural satellites that fell below their parent planet's Roche limit and were torn apart by tidal forces.
No secondary characteristics have been observed around extrasolar planets. The sub-brown dwarf Cha , which has been described as a rogue planet , is believed to be orbited by a tiny protoplanetary disc  and the sub-brown dwarf OTS 44 was shown to be surrounded by a substantial protoplanetary disk of at least 10 Earth masses.
From Wikipedia, the free encyclopedia. This article is about the astronomical object. For planets in astrology, see Planets in astrology.
For other uses, see Planet disambiguation. Class of astronomical body directly orbiting a star or stellar remnant. Further information: History of astronomy , Definition of planet , and Timeline of Solar System astronomy.
Main article: Babylonian astronomy. See also: Greek astronomy. Main articles: Indian astronomy and Hindu cosmology. Main articles: Astronomy in the medieval Islamic world and Cosmology in medieval Islam.
See also: Heliocentrism. Main article: IAU definition of planet. See also: List of former planets. See also: Weekday names and Naked-eye planet.
Main article: Nebular hypothesis. Supernova remnant ejecta producing planet-forming material. Solar System — sizes but not distances are to scale.
The Sun and the eight planets of the Solar System. The inner planets , Mercury , Venus , Earth , and Mars.
Main article: Solar System. See also: List of gravitationally rounded objects of the Solar System. Main article: Exoplanet.
Main article: Dwarf planet. Main article: Rogue planet. See also: Five-planet Nice model. Main article: Sub-brown dwarf.
Main article: Satellite planet. Main articles: Orbit and Orbital elements. Main article: Axial tilt. Main article: Clearing the neighbourhood.
Main article: Planetary mass. Main article: Planetary differentiation. Main articles: Atmosphere and Extraterrestrial atmospheres.
See also: Extraterrestrial skies. Main article: Magnetosphere. Main articles: Natural satellite and Planetary ring.
Astronomy portal Solar System portal Space portal. The official definition applies only to the Solar System, whereas the definition applies to planets around other stars.
The extrasolar planet issue was deemed too complex to resolve at the IAU conference. The term "satellite" had already begun to be used to distinguish such bodies from those around which they orbited "primary planets".
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