In the history of astronomy, a handful of Solar System bodies other than Jupiter have been counted as the fifth planet from the Sun.
There are three main ideas regarding hypothetical planets between Mars and Jupiter.
During the early 19th century, as asteroids were discovered, they were considered planets. Jupiter became the sixth planet with the discovery of Ceres in 1801. Soon, three more asteroids, Pallas (1802), Juno (1804), and Vesta (1807) were discovered. They were counted as separate planets, despite the fact that they share a single orbital spacing given by Titius–Bode law. Between 1845 and 1851, eleven additional asteroids were discovered and Jupiter had become the twentieth planet. At this point, astronomers began to classify asteroids as minor planets.[1] Following the reclassification of the asteroids in their own group, Jupiter became the fifth planet once again. With the redefinition of the term planet in August 2006, Ceres is now considered a dwarf planet.
See main article: Phaeton (hypothetical planet). The disruption theory suggests that a planet which was positioned between Mars and Jupiter was destroyed, resulting in the asteroid belt between these planets. Scientists in the 20th century dubbed this hypothetical planet "Phaeton". Today, the Phaeton hypothesis, superseded by the accretion model, has been discarded by the scientific community; however, some fringe scientists regard this theory as credible and even likely.
| Source: https://solarsystem.nasa.gov/planet-compare/ - (except Formulae-based Derivations below) | Mercury | Venus | Earth | Mars | Jupiter | Saturn | Uranus | Neptune |
| Orbit Distance(km) | 57909227 | 108209475 | 149598262 | 227943824 | 778340821 | 1426666422 | 2870658186 | 4498396441 |
| Equatorial Radius(km) | 2439.7 | 6051.8 | 6371 | 3389.5 | 69911 | 58232 | 25362 | 24622 |
| Volume(km3) | 60827208742 | 928415345893 | 1083206916846 | 163115609799 | 1431281810739360 | 827129915150897 | 68334355695584 | 62525703987421 |
| Mass(kg) | 3.30104E+023 | 4.86732E+024 | 5.97219E+024 | 6.41693E+023 | 1.89813E+027 | 5.68319E+026 | 8.68103E+025 | 1.0241E+026 |
| Density(g/cm3) | 5.427 | 5.243 | 5.513 | 3.934 | 1.326 | 0.687 | 1.27 | 1.638 |
| Surface Gravity(m/s2) | 3.7 | 8.87 | 9.80665 | 3.71 | 24.79 | 10.4* | 8.87 | 11.15 |
| Escape Velocity(km/h) | 15300 | 37296 | 40284 | 18108 | 216720 | 129924 | 76968 | 84816 |
| Rotation Period(Earth Days) | 58.646 | -243.018 | 0.99726968 | 1.026 | 0.41354 | 0.444 | -0.718 | 0.671 |
| Orbit Period(Earth Years) | 0.2408467 | 0.61519726 | 1.0000174 | 1.8808476 | 11.862615 | 29.447498 | 84.016846 | 164.79132 |
| Mean Orbit Velocity(km/h) | 170503 | 126074 | 107218 | 86677 | 47002 | 34701 | 24477 | 19566 |
| Orbit Eccentricity | 0.20563593 | 0.00677672 | 0.01671123 | 0.0933941 | 0.04838624 | 0.05386179 | 0.04725744 | 0.00859048 |
| Orbit Inclination | 7.0 degrees | 3.39 degrees | 0.00005 degrees | 1.85 degrees | 1.304 degrees | 2.49 degrees | 0.77 degrees | 1.77 degrees |
| Equatorial Inclination | 0 degrees | 177.3 degrees (retrograde rotation) | 23.4393 degrees | 25.2 | 3.1 degrees | 26.7 degrees | 97.8 degrees (retrograde rotation) | 28.3 degrees |
| Surface Temperature(°C) | -173/427 | 462 | -88/58 (min/max) | -153 to +20 | ||||
| Atmospheric Constituents | Carbon Dioxide, Nitrogen | Nitrogen, Oxygen | Carbon Dioxide, Nitrogen, Argon | Hydrogen, Helium | Hydrogen, Helium | Hydrogen, Helium, Methane | Hydrogen, Helium, Methane | |
| Moons | 0 | 0 | 1 | 2 | 95 | 84 | 27 | 14 |
| Rings | No | No | No | No | Yes | Yes | Yes | Yes |
| Planet Rotation Speed (km/h) - https://sos.noaa.gov/catalog/datasets/planet-rotations/|10.83|6.52|1574|866|45583|36840|14794|9719|-||||||||||-|FORMULAE-based DERIVATIONS:|||||||||-|Planet Circumference|15329.08|38024.57|40030.17|21296.85|439263.68|365882.37|159354.11|154704.56|-|Planet Orbit Length(km)|359976534.15|679894285.45|939889341.79|1429087909.61|4887629080.60|8957603967.91|18027106656.43|28264274873.77|-|No. of Planet Circumferences per Orbit Length|23483.2|17880.4|23479.5|67103.2|11126.9|24482.2|113126.1|182698.4|-||||||||||-|Similarity to Earth’s Orbit|1.0|0.8|1.0|2.9|0.5|1.0|4.8|7.8|-|||Deviation and also no magnetosphere||Deviation and also no magnetosphere|Expected deviation @ Jupiter & beyond||||-||||||||||-|Planet Surface Gravity vis Planet Rotation Speed |4427.7|17631.2|80.8|55.5|7.0|3.7|7.8|14.9|-|Planet Escape Velocity vis Planet Circumference|1.0|1.0|1.0|0.9|0.5|0.4|0.5|0.5|-||||||Expected deviation @ Jupiter & beyond||||-||||||||||-|Planet Density vis Planet Circumference|0.354|0.138|0.138|0.185|0.003|0.002|0.008|0.011|-|Similarity to Earth|1.9|1.0|1.0|1.3|0.02|0.01|0.06|0.08|-||Expected deviation @ closer to Sun|||Deviation|Expected deviation @ Jupiter & beyond||||} The similar deviations and missing magnetosphere[2] of Venus and Mars - combined with mass of total asteroid belt - and orbital characteristics and density of 10 Hygiea is a pointer. Planet V theorySee main article: Planet V. Based on simulations, NASA space scientists John Chambers and Jack J. Lissauer have proposed the existence of a planet between Mars and the asteroid belt, going in a successively eccentric and unstable orbit, 4 billion years ago. They connect this planet, which they name Planet V, and its disappearance with the Late Heavy Bombardment episode of the Hadean era.[3] [4] Chambers and Lissauer also claim this Planet V most probably ended up crashing into the Sun. Unlike the disruption theory's fifth planet, "Planet V" is not credited with creating the asteroid belt. Fifth planet in fictionThe concept of a fifth planet which had been destroyed to make the asteroid belt, as in the Disruption Theory, has been a popular one in fiction. See also
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