Jupiter (astronomy)


May 25, 2022

Jupiter (from the Latin Iovem, accusative of Iuppiter) is the fifth planet in the solar system in order of distance from the Sun and the largest of the entire planetary system: its mass corresponds to two and a half times the sum of those of all the others planets put together. It is classified, like Saturn, Uranus and Neptune, as a gas giant (the latter two differ in being classified in recent times as ice giants). Jupiter has a composition similar to that of the Sun: in fact it consists mainly of hydrogen and helium with small quantities of other compound gases, such as ammonia, methane and water. It is believed that the planet possesses a multi-layered structure, with a solid core, presumably of a rocky nature and consisting of carbon and iron silicates, upon which weigh a mantle of metallic hydrogen and a vast atmospheric cover that exert very high pressures on it. The external atmosphere is characterized by numerous bands and zones of shades varying from cream to brown, dotted with cyclonic and anticyclonic formations, among which the Great Red Spot stands out. The rapid rotation of the planet gives it the appearance of a flattened spheroid at the poles and generates an intense magnetic field that gives rise to an extensive magnetosphere; furthermore, due to the Kelvin-Helmholtz mechanism, Jupiter (like all other gas giants) emits more energy than it receives from the Sun. Due to its size and solar-like composition, Jupiter has been considered for a long time a "failed star": in reality only if it had had the opportunity to increase its mass up to 75-80 times the current one, its core would have hosted the conditions of temperature and pressure favorable to the triggering of fusion reactions hydrogen into helium, which would have made the solar system a binary star system. Jupiter's intense gravitational field affects the solar system in its structure by perturbing the orbits of other planets and "clearing" it in part of debris that may strike the innermost planets. Numerous satellites and a barely visible ring system orbit around Jupiter; the combined action of the gravitational fields of Jupiter and the Sun also stabilizes the orbits of two groups of Trojan asteroids.The planet, known since ancient times, has played a preponderant role in the religious belief of numerous cultures, including the Babylonians , the Greeks and Romans, who identified him with the ruler of the gods. The astronomical symbol of the planet (♃) is a stylized representation of the lightning bolt, the main attribute of that deity.


Jupiter appears to the naked eye as a very bright whitish star due to its high albedo. It is the fourth brightest object in the sky, after the Sun, the Moon and Venus with which, when the latter is undetectable, it shares the role of "morning star" or "evening star". Its apparent magnitude varies, depending on the position during its revolution, from −1.6 to −2.8, while its apparent diameter varies from 29.8 to 50.1 seconds of arc. of the planet is 398.88 days, at the end of which the celestial body begins a phase of apparent retrograde motion, in which it seems to move backwards in the night sky with respect to the background of the "fixed" stars, following a sigmoid trajectory. Jupiter, in about 12 years of its own revolution, crosses all the constellations of the zodiac. The planet is interesting from an observational point of view as already with small instruments it is possible to appreciate some characteristic surface details. The most propitious periods to observe the planet correspond to the oppositions and in particular to the "great oppositions", which occur every time Jupiter passes through the perihelion. These circumstances, in