|
| asc_node = 100.464° | arg_peri = 273.867° | mean_anomaly = 20.020° | period = | synodic_period = 〔 | avg_speed = 13.07 km/s〔 | satellites = 67 () | physical_characteristics = yes | flattening = | equatorial_radius = | polar_radius = | mean_radius = 〔〔 | surface_area = | volume = | mass = | density = 〔〔 | surface_grav = 〔〔 2.528 g | escape_velocity = 59.5 km/s〔〔 | sidereal_day = 9.925 h (9 h 55 m 30 s) | rot_velocity = 12.6 km/s | axial_tilt = 3.13° (to orbit)〔 | right_asc_north_pole = 268.057° 〔 | declination = 64.496°〔 | albedo = 0.343 (Bond) 0.52 (geom.)〔 | magnitude = to 〔 | angular_size = 29.8″ to 50.1″〔 | pronounced = 〔Jupiter, entry in the Oxford English Dictionary, prepared by J. A. Simpson and E. S. C. Weiner, vol. 8, second edition, Oxford: Clarendon Press, 1989. ISBN 0-19-861220-6 (vol. 8), ISBN 0-19-861186-2 (set.)〕 | adjectives = Jovian | temperatures = yes | temp_name1 = 1 bar level | min_temp_1 = | mean_temp_1 = 165 K (−108 °C)〔 | max_temp_1 = | temp_name2 = 0.1 bar | min_temp_2 = | mean_temp_2 = 112 K〔 | max_temp = | atmosphere = yes | atmosphere_ref = 〔 | surface_pressure = 20–200 kPa (cloud layer) | scale_height = 27 km | atmosphere_composition = by volume: Ices: * ammonia (NH3) * water (H2O) * ammonium hydrosulfide (NH4SH) }} Jupiter is the fifth planet from the Sun and the largest in the Solar System. It is a giant planet with a mass one-thousandth that of the Sun, but two and a half times that of all the other planets in the Solar System combined. Jupiter is a gas giant, along with Saturn (Uranus and Neptune are ice giants). Jupiter was known to astronomers of ancient times. The Romans named it after their god Jupiter. When viewed from Earth, Jupiter can reach an apparent magnitude of −2.94, bright enough for its reflected light to cast shadows, and making it on average the third-brightest object in the night sky after the Moon and Venus. Jupiter is primarily composed of hydrogen with a quarter of its mass being helium, although helium only comprises about a tenth of the number of molecules. It may also have a rocky core of heavier elements, but like the other giant planets, Jupiter lacks a well-defined solid surface. Because of its rapid rotation, the planet's shape is that of an oblate spheroid (it has a slight but noticeable bulge around the equator). The outer atmosphere is visibly segregated into several bands at different latitudes, resulting in turbulence and storms along their interacting boundaries. A prominent result is the Great Red Spot, a giant storm that is known to have existed since at least the 17th century when it was first seen by telescope. Surrounding Jupiter is a faint planetary ring system and a powerful magnetosphere. Jupiter has at least 67 moons, including the four large Galilean moons discovered by Galileo Galilei in 1610. Ganymede, the largest of these, has a diameter greater than that of the planet Mercury. Jupiter has been explored on several occasions by robotic spacecraft, most notably during the early ''Pioneer'' and ''Voyager'' flyby missions and later by the Galileo orbiter. Jupiter was most recently visited by a probe in late February 2007, when ''New Horizons'' used Jupiter's gravity to increase its speed and bend its trajectory en route to Pluto. The next probe to visit the planet will be ''Juno'', which is expected to arrive in July 2016. Future targets for exploration in the Jupiter system include the probable ice-covered liquid ocean of its moon Europa. ==Formation and migration== (詳細はsuper-Earths may have originally populated the inner Solar System. --> Earth and its neighbor planets may have formed from fragments of planets after collisions with Jupiter destroyed those super-Earths near the Sun. As Jupiter came toward the inner Solar System, in what theorists call the Grand Tack Hypothesis, gravitational tugs and pulls occurred causing a series of collisions between the super-Earths as their orbits began to overlap. Astronomers have discovered nearly 500 planetary systems each with multiple planets, and typically these systems include a few planets with masses several times greater than Earth's (super-Earths), orbiting closer to their star than Mercury is to the Sun, and Jupiter-like gas giants are also often found close to their star. Jupiter moving out of the inner Solar System would have allowed the formation of inner planets, including Earth. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Jupiter」の詳細全文を読む スポンサード リンク
|