Ten Planets: Stories

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See also: Kepler's laws of planetary motion and Exoplanetology §Orbital parameters The orbit of the planet Neptune compared to that of Pluto. Note the elongation of Pluto's orbit in relation to Neptune's ( eccentricity), as well as its large angle to the ecliptic ( inclination). Earth rotates on its axis at 1,532 feet per second (467 meters per second) — slightly more than 1,000 mph (1,600 kph) — at the equator. The planet zips around the sun at more than 18 miles per second (29 km per second). The eight planets of the Solar System with size to scale (up to down, left to right): Saturn, Jupiter, Uranus, Neptune (outer planets), Earth, Venus, Mars, and Mercury (inner planets) According to the IAU definition, there are eight planets in the Solar System, which are (in increasing distance from the Sun): [1] Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune. Jupiter is the largest, at 318 Earth masses, whereas Mercury is the smallest, at 0.055 Earth masses. [151] Burnet, John (1950). Greek philosophy: Thales to Plato. Macmillan and Co. pp.7–11. ISBN 978-1-4067-6601-1 . Retrieved 7 February 2008.

Earth's name in English is not derived from Greco-Roman mythology. Because it was only generally accepted as a planet in the 17thcentury, [34] 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 Old English word eorþe, which was the word for "ground" and "dirt" as well as the world itself. [93] As with its equivalents in the other Germanic languages, it derives ultimately from the Proto-Germanic word erþō, as can be seen in the English earth, the German Erde, the Dutch aarde, and the Scandinavian jord. 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". [94] The non-Romance languages use their own native words. The Greeks retain their original name, Γή (Ge). [95]It is smaller than Earth's moon; its orbit is highly elliptical, falling inside Neptune's orbit at some points and far beyond it at others; and Pluto's orbit doesn't fall on the same plane as all the other planets — instead, it orbits 17.1 degrees above or below, taking 288 years to complete a single orbit according to ESA. a b c d Chen, Jingjing; Kipping, David (2016). "Probabilistic Forecasting of the Masses and Radii of Other Worlds". The Astrophysical Journal. 834 (1): 17. arXiv: 1603.08614. doi: 10.3847/1538-4357/834/1/17. S2CID 119114880. Main article: Solar System The Solar System, including the Sun, planets, dwarf planets, and the larger moons (except Iapetus). Distances between the bodies are not to scale. Dwarf planets had been proposed as a category of small planet (as opposed to planetoids as sub-planetary objects) and planetary geologists continue to treat them as planets despite the IAU definition. [61] The largest known trans-Neptunian objects with their moons; the Earth and Moon have been added for comparison. All pictures are artist's impressions except for the Pluto and Earth systems.

But that restrictive definition helped isolate what should and should not be considered a planet — a problem that arose as astronomers discovered more and more planet-like objects in the solar system. Pluto was among the bodies that didn't make the cut and was re-classified as a dwarf planet. Uranus holds the record for the coldest temperature ever measured in the solar system — minus 371.56 degrees F (minus 224.2 degrees C). The average temperature of Uranus is minus 320 degrees Fahrenheit (-195 degrees Celsius). The idea of planets has evolved over its history, from the divine lights of antiquity to the earthly objects of the scientific age. The concept has expanded to include worlds not only in the Solar System, but in multitudes of other extrasolar systems. The consensus definition as to what counts as a planet vs. other objects orbiting the Sun has changed several times, previously encompassing asteroids, moons, and dwarf planets like Pluto, [5] [6] [7] and there continues to be some disagreement today. [7] Brown, Michael E. "The Dwarf Planets". California Institute of Technology, Department of Geological Sciences . Retrieved 26 January 2008. The Oort Cloud lies well past the Kuiper Belt, considered to be located between 2,000 and 5,000 astronomical units (AU) from the sun. The outer edge of the Oort Cloud may reach as far as 10,000 up to 100,000 AU from the sun. One AU is equal to approximately 93,000,000 miles (150 million kilometers). The Oort Cloud is home to billions, or even trillions of objects, according to NASA Science. Solar system formation and discoveryStilbon with its speedy motion, was ruled over by Hermes, messenger of the gods and god of learning and wit. [17] The semi-major axis gives the size of the orbit. It is the distance from the midpoint to the longest diameter of its elliptical orbit. This distance is not the same as its apastron, because no planet's orbit has its star at its exact centre. [182] Mercury is the closest planet to the sun and the smallest planet in the solar system — it is only a little larger than Earth's moon. Mercury zips around the sun in only 88 days and because it is so close to our star (about two-fifths the distance between Earth and the sun). A planet is a large, rounded astronomical body that is neither a star nor its remnant. The best available theory of planet formation is the nebular hypothesis, which posits that an interstellar cloud collapses out of a nebula to create a young protostar orbited by a protoplanetary disk. Planets grow in this disk by the gradual accumulation of material driven by gravity, a process called accretion. The Solar System has at least eight planets: the terrestrial planets Mercury, Venus, Earth, and Mars, and the giant planets Jupiter, Saturn, Uranus, and Neptune. (When the term "planet" is applied more broadly, these eight uncontroversial planets can be distinguished by calling them "major planets".) These planets each rotate around an axis tilted with respect to its orbital pole. All the major planets of the Solar System other than Mercury possess a considerable atmosphere, and some share such features as ice caps, seasons, volcanism, hurricanes, tectonics, and even hydrology. Apart from Venus and Mars, the Solar System planets generate magnetic fields, and all the major planets except Venus and Mercury have natural satellites. The giant planets bear planetary rings, the most prominent being those of Saturn. Brown, Mike (23 February 2021). "How Many Dwarf Planets Are There in the Outer Solar System?". California Institute of Technology. Archived from the original on 19 July 2022 . Retrieved 11 August 2022.

Its swirling clouds are colorful due to different types of trace gases including ammonia ice, ammonium hydrosulfide crystals as well as water ice and vapor. There have been five human-made objects so far, Voyager 1, Voyager 2, New Horizons, Pioneer 10 and Pioneer 11, that have crossed the threshold into interstellar space. In 2016, researchers proposed the possible existence of a ninth planet, for now, dubbed "Planet Nine" or Planet X. The planet is estimated to be about 10 times the mass of Earth and to orbit the sun between 300 and 1,000 times farther than the orbit of the Earth. O'Connor, J. J.; Robertson, E. F. "Aryabhata the Elder". MacTutor History of Mathematics archive . Retrieved 10 July 2022.

Recent Videos & Visualizations Above the Earth, Below the Surface: Landsat's Role in Monitoring Water Quality Planetary geologists may include the nineteen known planetary-mass moons as "satellite planets", including Earth's Moon and Pluto's Charon, like the early modern astronomers. [3] [65] Some go even further and include as planets relatively large, geologically evolved bodies that are nonetheless not very round today, such as Pallas and Vesta; [3] rounded bodies that were completely disrupted by impacts and re-accreted like Hygiea; [66] [67] [68] or even everything at least the diameter of Saturn's moon Mimas, the smallest planetary-mass moon. (This may even include objects that are not round but happen to be larger than Mimas, like Neptune's moon Proteus.) [3] a b Margot, Jean-Luc (2015). "A quantitative criterion for defining planets". The Astronomical Journal. 150 (6): 185. arXiv: 1507.06300. Bibcode: 2015AJ....150..185M. doi: 10.1088/0004-6256/150/6/185. S2CID 51684830. The eccentricity of an orbit describes the elongation of a planet's elliptical (oval) orbit. Planets with low eccentricities have more circular orbits, whereas planets with high eccentricities have more elliptical orbits. The planets and large moons in the Solar System have relatively low eccentricities, and thus nearly circular orbits. [182] The comets and many Kuiper belt objects, as well as several extrasolar planets, have very high eccentricities, and thus exceedingly elliptical orbits. [184] [185] Brown, Michael E., and Konstantin Batygin. " Observational constraints on the orbit and location of planet nine in the outer solar system." The Astrophysical Journal Letters 824.2 (2016): L23.