Auch die 17entdeckten Planeten Uranus und Neptun sowie der entdeckte Zwergplanet Pluto – bis IMP-Schülerinnen erstellen Planeten-Wiki. Da die Lernplattform „Moodle“ am St.-Dominikus-Gymnasium schon seit zehn Jahren eingesetzt wird, konnte sie sehr. Und zwar die vier inneren Gesteinsplaneten, die recht klein sind: Merkur, Venus, Erde und Mars. Dann – immer von der Sonne nach außen gesehen – die vier.
IMP-Schülerinnen erstellen Planeten-WikiEin Planet ist ein großer Himmelskörper, der sich um eine Sonne bewegt. Das Klexikon ist wie eine Wikipedia für Kinder und Schüler. Ein Planet ist ein stellares Objekt, welches in der Regel einen Stern auf einer Umlaufbahn. Ein Planet (des Sonnensystems) ist gemäß der Definition der Internationalen Astronomischen Union (IAU) ein Himmelskörper,. (a) der sich auf einer.
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Segui i suggerimenti del progetto di riferimento. He was, however, partial to his own favourite movement, Saturn. Adrian Boult . Balfour Gardiner.
It was hastily rehearsed; the musicians of the Queen's Hall Orchestra first saw the complicated music only two hours before the performance, and the choir for Neptune was recruited from pupils from Morley College and St Paul's Girls' School where Holst taught.
It was a comparatively intimate affair, attended by around invited associates,    but Holst regarded it as the public premiere, inscribing Boult's copy of the score, "This copy is the property of Adrian Boult who first caused the Planets to shine in public and thereby earned the gratitude of Gustav Holst.
A public concert was given in London under the auspices of the Royal Philharmonic Society on 27 February , conducted by Boult.
He felt that when the public were being given a totally new language like that, "half an hour of it was as much as they could take in". It is not clear whether this performance was conducted by Appleby Matthews  or the composer.
His daughter Imogen recalled, "He hated incomplete performances of The Planets , though on several occasions he had to agree to conduct three or four movements at Queen's Hall concerts.
He particularly disliked having to finish with Jupiter, to make a 'happy ending', for, as he himself said, 'in the real world the end is not happy at all'".
This was the first time the movement Neptune had been heard in a public performance, all the other movements having been given earlier public airings.
The composer conducted a complete performance for the first time on 13 October , with the Queen's Hall Orchestra at a Promenade Concert.
Holst conducted the LSO in two recorded performances of The Planets : the first was an acoustic recording made in sessions between and now available on Pavilion Records' Pearl label ; the second was made in , and utilised the then-new electrical recording process in , this was released on compact disc by IMP and later on Naxos outside the United States.
The work is scored for a large orchestra consisting of the following instrumentation. The movements vary in the combinations of instruments used.
In "Neptune", two three-part women's choruses each comprising two soprano sections and one alto section located in an adjoining room which is to be screened from the audience are added.
The suite has seven movements, each named after a planet and its corresponding astrological character see Planets in astrology :. Holst's original title, as seen on the handwritten full score, was "Seven Pieces for Large Orchestra".
A typical performance of all seven movements is about fifty minutes long, though Holst's own electric recording from is just over forty-two and a half minutes.
One explanation for the suite's structure, presented by Holst scholar Raymond Head, is the ruling of astrological signs of the zodiac by the planets:  if the signs are listed along with their ruling planets in the traditional order starting with Aries , ignoring duplication and the luminaries the Sun and Moon , the order of the movements corresponds.
National Space Science Data Center. Retrieved 10 September November Archived from the original PDF on 4 March Nature : — BBC News.
Retrieved 29 November Retrieved 25 December Retrieved 31 January Bibcode : NatGe.. Retrieved 17 January Retrieved 8 August HITRAN is a compilation of spectroscopic parameters that a variety of computer codes use to predict and simulate the transmission and emission of light in the atmosphere.
Zuev Institute of Atmospheric Optics. Retrieved 11 August September Bibcode : CosRe Introduction to Space Physics.
In Shirley, J. Encyclopedia of Planetary Sciences. New York: Chapman and Hall. Earth and Planetary Science Letters. Retrieved 28 June Archived from the original on 12 May Oliver Hawkins, more or less alumnus and statistical legend, wrote some code for us, which calculated which planet was closest to the Earth on each day for the past 50 years, and then sent the results to David A.
Rothery , professor of planetary geosciences at the Open University. Archived from the original on 9 August Retrieved 19 March Retrieved 7 January The simplest way to determine the correct figure is to multiply Earth's radius of 6 m WGS84 and Earth's angular speed, 7.
The incorrect figure of But the correct speed must be relative to inertial space, so the stellar day of 86 The Cambridge Planetary Handbook.
Venus Express. Archived from the original on 11 May Retrieved 20 January Archived from the original on 18 February Solar System Voyage.
Translated by Dunlop, Storm. June Astrophysical Journal. Bibcode : ApJ Monthly Notices of the Royal Astronomical Society. Scientific American. Buffalo, NY: Firefly Books.
Retrieved 11 January Archived from the original on 17 August University of Central Lancashire. Archived from the original on 30 July Retrieved 14 May NBC News.
Archived from the original on 18 June Transits of the Sun. University College London. Retrieved 11 May Philosophical Transactions of the Royal Society.
Notes and Records of the Royal Society of London. The Gallery of Natural Phenomena. Journal of the British Astronomical Association. Bibcode : JBAA..
Philosophical Transactions of the Royal Society of London. PDF Ph. Understanding Planets in Ancient Mesopotamia.
Folklore Vol. Science and Civilisation in China: Volume 3. Cambridge: Cambridge University Press. Bibcode : scc3. Natural History II— Harmondsworth, Middlesex, UK: Penguin.
Lore and Science in Ancient Pythagoreanism. Harvard University Press. Bibcode : Isis Mathematics and Physical Sciences".
Encyclopedia Iranica. Razaullah Ansari Vaquero; M. The Sun Recorded Through History. Journal for the History of Astronomy.
Bibcode : JHA Heinrich D. Holland; Karl K. Turekian eds. Treatise on Geochemistry. Bibcode : tvnv. Retrieved 10 May Kurtz ed. Mikhail Lomonosov and the discovery of the atmosphere of Venus during the transit.
Preston, U. Astronomische Nachrichten. Storms such as this are common within the turbulent atmospheres of giant planets. Jupiter also has white ovals and brown ovals, which are lesser unnamed storms.
White ovals tend to consist of relatively cool clouds within the upper atmosphere. Brown ovals are warmer and located within the "normal cloud layer".
Such storms can last as little as a few hours or stretch on for centuries. Even before Voyager proved that the feature was a storm, there was strong evidence that the spot could not be associated with any deeper feature on the planet's surface, as the Spot rotates differentially with respect to the rest of the atmosphere, sometimes faster and sometimes more slowly.
In , an atmospheric feature formed in the southern hemisphere that is similar in appearance to the Great Red Spot, but smaller.
This was created when several smaller, white oval-shaped storms merged to form a single feature—these three smaller white ovals were first observed in It has since increased in intensity and changed color from white to red.
They found that, while the Spot changes size, shape and intensity over the short term, it has maintained its general position in the atmosphere across more than 15 years of available data.
Scientists believe the Spot is a giant vortex similar to the Great Red Spot and also appears to be quasi-stable like the vortices in Earth's thermosphere.
Interactions between charged particles generated from Io and the planet's strong magnetic field likely resulted in redistribution of heat flow, forming the Spot.
Jupiter's magnetic field is fourteen times as strong as that of Earth, ranging from 4. The volcanoes on the moon Io emit large amounts of sulfur dioxide , forming a gas torus along the moon's orbit.
The gas is ionized in the magnetosphere, producing sulfur and oxygen ions. They, together with hydrogen ions originating from the atmosphere of Jupiter, form a plasma sheet in Jupiter's equatorial plane.
The plasma in the sheet co-rotates with the planet, causing deformation of the dipole magnetic field into that of a magnetodisk.
Electrons within the plasma sheet generate a strong radio signature that produces bursts in the range of 0. At about 75 Jupiter radii from the planet, the interaction of the magnetosphere with the solar wind generates a bow shock.
Surrounding Jupiter's magnetosphere is a magnetopause , located at the inner edge of a magnetosheath —a region between it and the bow shock.
The solar wind interacts with these regions, elongating the magnetosphere on Jupiter's lee side and extending it outward until it nearly reaches the orbit of Saturn.
The four largest moons of Jupiter all orbit within the magnetosphere, which protects them from the solar wind.
The magnetosphere of Jupiter is responsible for intense episodes of radio emission from the planet's polar regions.
Volcanic activity on Jupiter's moon Io see below injects gas into Jupiter's magnetosphere, producing a torus of particles about the planet.
As a result, radio waves are generated through a cyclotron maser mechanism , and the energy is transmitted out along a cone-shaped surface.
When Earth intersects this cone, the radio emissions from Jupiter can exceed the solar radio output.
This is approximately two-fifths the orbital period of Saturn, forming a near orbital resonance between the two largest planets in the Solar System.
Because the eccentricity of its orbit is 0. The axial tilt of Jupiter is relatively small: only 3. As a result, it does not experience significant seasonal changes, in contrast to, for example, Earth and Mars.
Jupiter's rotation is the fastest of all the Solar System's planets, completing a rotation on its axis in slightly less than ten hours; this creates an equatorial bulge easily seen through an Earth-based amateur telescope.
The planet is shaped as an oblate spheroid , meaning that the diameter across its equator is longer than the diameter measured between its poles.
Because Jupiter is not a solid body, its upper atmosphere undergoes differential rotation. System II applies at all latitudes north and south of these; its period is 9h 55m System III was first defined by radio astronomers , and corresponds to the rotation of the planet's magnetosphere; its period is Jupiter's official rotation.
Jupiter is usually the fourth brightest object in the sky after the Sun, the Moon and Venus ;  at times Mars is brighter than Jupiter.
Earth overtakes Jupiter every As it does so, Jupiter appears to undergo retrograde motion with respect to the background stars.
That is, for a period Jupiter seems to move backward in the night sky, performing a looping motion. Because the orbit of Jupiter is outside that of Earth, the phase angle of Jupiter as viewed from Earth never exceeds It was only during spacecraft missions to Jupiter that crescent views of the planet were obtained.
The planet Jupiter has been known since ancient times. It is visible to the naked eye in the night sky and can occasionally be seen in the daytime when the Sun is low.
They used Jupiter's roughly year orbit along the ecliptic to define the constellations of their zodiac. The astronomical symbol for the planet, , is a stylized representation of the god's lightning bolt.
The original Greek deity Zeus supplies the root zeno- , used to form some Jupiter-related words, such as zenographic. Jovian is the adjectival form of Jupiter.
The older adjectival form jovial , employed by astrologers in the Middle Ages , has come to mean "happy" or "merry", moods ascribed to Jupiter's astrological influence.
In Vedic astrology , Hindu astrologers named the planet after Brihaspati , the religious teacher of the gods, and often called it " Guru ", which literally means the "Heavy One".
In Central Asian Turkic myths , Jupiter is called Erendiz or Erentüz , from eren of uncertain meaning and yultuz "star". There are many theories about the meaning of eren.
These peoples calculated the period of the orbit of Jupiter as 11 years and days. They believed that some social and natural events connected to Erentüz's movements on the sky.
The observation of Jupiter dates back to at least the Babylonian astronomers of the 7th or 8th century BC.
By the 4th century BC, these observations had developed into the Chinese zodiac ,  with each year associated with a Tai Sui star and god controlling the region of the heavens opposite Jupiter's position in the night sky; these beliefs survive in some Taoist religious practices and in the East Asian zodiac's twelve animals, now often popularly assumed to be related to the arrival of the animals before Buddha.
If accurate, this would predate Galileo's discovery by nearly two millennia. In , Italian polymath Galileo Galilei discovered the four largest moons of Jupiter now known as the Galilean moons using a telescope; thought to be the first telescopic observation of moons other than Earth's.
One day after Galileo, Simon Marius independently discovered moons around Jupiter, though he did not publish his discovery in a book until These findings were also the first discovery of celestial motion not apparently centered on Earth.
The discovery was a major point in favor of Copernicus' heliocentric theory of the motions of the planets; Galileo's outspoken support of the Copernican theory placed him under the threat of the Inquisition.
During the s, Giovanni Cassini used a new telescope to discover spots and colorful bands on Jupiter and observed that the planet appeared oblate; that is, flattened at the poles.
He was also able to estimate the rotation period of the planet. The Great Red Spot, a prominent oval-shaped feature in the southern hemisphere of Jupiter, may have been observed as early as by Robert Hooke and in by Cassini, although this is disputed.
The pharmacist Heinrich Schwabe produced the earliest known drawing to show details of the Great Red Spot in The Red Spot was reportedly lost from sight on several occasions between and before becoming quite conspicuous in It was recorded as fading again in and at the start of the 20th century.
Both Giovanni Borelli and Cassini made careful tables of the motions of Jupiter's moons, allowing predictions of the times when the moons would pass before or behind the planet.
In , E. The discovery of this relatively small object, a testament to his keen eyesight, quickly made him famous.
This moon was later named Amalthea. In , Rupert Wildt identified absorption bands of ammonia and methane in the spectra of Jupiter.
Three long-lived anticyclonic features termed white ovals were observed in For several decades they remained as separate features in the atmosphere, sometimes approaching each other but never merging.
Finally, two of the ovals merged in , then absorbed the third in , becoming Oval BA. In , Bernard Burke and Kenneth Franklin detected bursts of radio signals coming from Jupiter at Radio bursts from Jupiter were found to come in two forms: long bursts or L-bursts lasting up to several seconds, and short bursts or S-bursts that had a duration of less than a hundredth of a second.
Since , a number of automated spacecraft have visited Jupiter, most notably the Pioneer 10 space probe, the first spacecraft to get close enough to Jupiter to send back revelations about the properties and phenomena of the Solar System's largest planet.
Entering a Hohmann transfer orbit from Earth to Jupiter from low Earth orbit requires a delta-v of 6. Beginning in , several spacecraft have performed planetary flyby maneuvers that brought them within observation range of Jupiter.
The Pioneer missions obtained the first close-up images of Jupiter's atmosphere and several of its moons. They discovered that the radiation fields near the planet were much stronger than expected, but both spacecraft managed to survive in that environment.
The trajectories of these spacecraft were used to refine the mass estimates of the Jovian system. Radio occultations by the planet resulted in better measurements of Jupiter's diameter and the amount of polar flattening.
Six years later, the Voyager missions vastly improved the understanding of the Galilean moons and discovered Jupiter's rings.
They also confirmed that the Great Red Spot was anticyclonic. Comparison of images showed that the Red Spot had changed hue since the Pioneer missions, turning from orange to dark brown.
A torus of ionized atoms was discovered along Io's orbital path, and volcanoes were found on the moon's surface, some in the process of erupting.
As the spacecraft passed behind the planet, it observed flashes of lightning in the night side atmosphere. The next mission to encounter Jupiter was the Ulysses solar probe.
It performed a flyby maneuver to attain a polar orbit around the Sun. In the 11th century, the transit of Venus was observed by Avicenna , who established that Venus was, at least sometimes, below the Sun.
With the advent of the Scientific Revolution , use of the term "planet" changed from something that moved across the sky in relation to the star field ; to a body that orbited Earth or that was believed to do so at the time ; and by the 18th century to something that directly orbited the Sun when the heliocentric model of Copernicus , Galileo and Kepler gained sway.
Thus, Earth became included in the list of planets,  whereas the Sun and Moon were excluded. At first, when the first satellites of Jupiter and Saturn were discovered in the 17th century, the terms "planet" and "satellite" were used interchangeably — although the latter would gradually become more prevalent in the following century.
In the 19th century astronomers began to realize that recently discovered bodies that had been classified as planets for almost half a century such as Ceres , Pallas , Juno , and Vesta were very different from the traditional ones.
These bodies shared the same region of space between Mars and Jupiter the asteroid belt , and had a much smaller mass; as a result they were reclassified as " asteroids ".
In the absence of any formal definition, a "planet" came to be understood as any "large" body that orbited the Sun. Because there was a dramatic size gap between the asteroids and the planets, and the spate of new discoveries seemed to have ended after the discovery of Neptune in , there was no apparent need to have a formal definition.
In the 20th century, Pluto was discovered. After initial observations led to the belief that it was larger than Earth,  the object was immediately accepted as the ninth planet.
Further monitoring found the body was actually much smaller: in , Ray Lyttleton suggested that Pluto may be an escaped satellite of Neptune ,  and Fred Whipple suggested in that Pluto may be a comet.
Then, on October 6, , Michel Mayor and Didier Queloz of the Geneva Observatory announced the first definitive detection of an exoplanet orbiting an ordinary main-sequence star 51 Pegasi.
The discovery of extrasolar planets led to another ambiguity in defining a planet: the point at which a planet becomes a star.
Many known extrasolar planets are many times the mass of Jupiter, approaching that of stellar objects known as brown dwarfs.
Brown dwarfs are generally considered stars due to their ability to fuse deuterium , a heavier isotope of hydrogen. Although objects more massive than 75 times that of Jupiter fuse hydrogen, objects of only 13 Jupiter masses can fuse deuterium.
Deuterium is quite rare, and most brown dwarfs would have ceased fusing deuterium long before their discovery, making them effectively indistinguishable from supermassive planets.
With the discovery during the latter half of the 20th century of more objects within the Solar System and large objects around other stars, disputes arose over what should constitute a planet.
There were particular disagreements over whether an object should be considered a planet if it was part of a distinct population such as a belt , or if it was large enough to generate energy by the thermonuclear fusion of deuterium.
A growing number of astronomers argued for Pluto to be declassified as a planet, because many similar objects approaching its size had been found in the same region of the Solar System the Kuiper belt during the s and early s.
Pluto was found to be just one small body in a population of thousands. Some of them, such as Quaoar , Sedna , and Eris , were heralded in the popular press as the tenth planet , failing to receive widespread scientific recognition.
Acknowledging the problem, the IAU set about creating the definition of planet , and produced one in August The number of planets dropped to the eight significantly larger bodies that had cleared their orbit Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune , and a new class of dwarf planets was created, initially containing three objects Ceres , Pluto and Eris.
There is no official definition of extrasolar planets. The positions statement incorporates the following guidelines, mostly focused upon the boundary between planets and brown dwarfs: .
This working definition has since been widely used by astronomers when publishing discoveries of exoplanets in academic journals. It does not address the dispute over the lower mass limit,  and so it steered clear of the controversy regarding objects within the Solar System.
This definition also makes no comment on the planetary status of objects orbiting brown dwarfs, such as 2Mb.
One definition of a sub-brown dwarf is a planet-mass object that formed through cloud collapse rather than accretion.
This formation distinction between a sub-brown dwarf and a planet is not universally agreed upon; astronomers are divided into two camps as whether to consider the formation process of a planet as part of its division in classification.
For example, a planet formed by accretion around a star may get ejected from the system to become free-floating, and likewise a sub-brown dwarf that formed on its own in a star cluster through cloud collapse may get captured into orbit around a star.
The 13 Jupiter-mass cutoff represents an average mass rather than a precise threshold value. 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 but no longer considered as such by the IAU, as well as whether they would be considered planets under Stern's and definitions.
Ceres was subsequently classified by the IAU as a dwarf planet in The reporting of newly discovered large Kuiper belt objects as planets - particularly Eris - triggered the August IAU decision on what a planet is.
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. Objecten die zich in een baan buiten Neptunus bevinden, maar nog steeds om de Zon draaien, worden ook geclassificeerd als transneptunisch object.
Pluto werd lang als planeet beschouwd, maar met de ontdekking van Eris in kwam de status van Pluto ter discussie te staan.
De IAU nam daarop de bovenstaande definitie aan, waardoor Pluto de planeetstatus verloor. Het verschil tussen een bruine dwerg en een planeet is dat bij de eerste wel enige kernfusie plaatsvindt en bij planeten niet.
Ook is de ontstaanswijze anders. Ten slotte verschilt een planeet van een maan omdat een planeet rond een ster beweegt. Bij een maan ligt het gemeenschappelijke zwaartepunt waaromheen beide objecten draaien binnen de oppervlakte van de planeet.
Wanneer de massa van de maan groot genoeg is om het massamiddelpunt buiten het oppervlakte van de planeet te plaatsen, spreekt men van een dubbelplaneet.
Bij de dwergplaneet Pluto en diens maan Charon ligt dit punt buiten Pluto, zodat er sprake is van een dubbeldwergplaneet.
Omdat Charon kleiner is dan Pluto, wordt Charon desondanks vaak als maan beschouwd. Enkele relatief dicht bij de Aarde staande planeten zijn in de oudheid al beschreven doordat zij met het blote oog zichtbaar zijn.
Mercurius was rond v.