木星(Jupiter)

太阳的第五个行星，太阳系中最大的非恒星物体。质量是地球的318倍，体积则超过1,400倍。巨大的质量使它在大气顶部有地球2.5倍的引力，对太阳系的其他成员产生强烈的影响。它造成了小行星带的柯克伍德缝和彗星的运动改变；它可以充当「哨兵」，牵引那些可能撞击其他行星的物体。木星至少有16个卫星，还有一个不到1公里宽的漫射环系统，这是「旅行者号」太空船在1979年发现的。这个行星是气体巨物，主要包含氢和氦，其比例与太阳接近，并以7.78亿公里的平均距离每12年绕日一周。自转速度很快（一圈9小时又55.5分），所产生的电流使它具有行星中最大的电场，并造成强烈的雷暴，包括一个已经持续千百年的雷暴（大红斑）。人们对其内部所知极少，但推测它有固态核心。中心温度估计为25,000℃，辐射热大於从太阳接收的热量，可能肇因於行星形成时残留的热量。

English version：

Jupiter

Fifth planet from the sun, the largest nonstellar object in the solar system. It has 318 times the mass and over 1,400 times the volume of earth. Its enormous mass gives it over 2.5 times the gravity of earth at the top of its atmosphere, and exerts strong effects on other members of the solar system. It is responsible for the Kirkwood gaps in the asteroid belt and changes in the motions of comets; it may act as a “sentinel,” pulling in bodies that might otherwise collide with other planets. Jupiter has at least 16 moons (see Galilean satellite) and a diffuse ring system less than 0.6 mi (1 km) thick, discovered in 1979 by the Voyager spacecraft. The planet is a gas giant, composed mainly of hydrogen and helium in proportions near those of the sun, which it orbits every 12 years at an average distance of 484 million mi (778 million km). Its rapid rotation (9 hours, 55.5 minutes) acts on electric currents to give it the largest magnetic field of any of the planets and causes intense storms, including one that has lasted hundreds of years (the Great Red Spot). Little is known of its interior, but it is presumed to have a solid core. Its central temperature is estimated to be 45,000°F (25,000°C); it radiates more heat than it receives from the sun, probably largely heat left over from its formation.