The next biggest moon is Callisto, at 4800 km in diameter.

第二大星是木四（卡利斯托），直径约4800公里。

That means the surface is very old, maybe as old as Callisto itself.

这意味着它的表面非常古老，可能和木四同岁。

They're called Ganymede, Callisto, and Europa.

这几个分别叫木、木四和木二。

Callisto orbits Jupiter farthest out of the four biggies, almost two million km away.

在四个大行星中，木四的公转轨离木星最远，约达200万千米。

The four largest moons, Io, Europa, Ganymede, and Callisto, are large enough to be seen from Earth with a telescope.

从地球上就可以用望远镜看到最大的四星，木一，木二，木，木四。

Juice will investigate three of the so-called Galilean moons-Callisto, Europa and Ganymede, all of which are thought to have subsurface oceans.

“果汁”探测器将调查所谓的伽利略星——木四、木二和木，这星都被认为拥有地下海洋。

In 1610, for example, Galileo used the first telescope to discover Jupiter's moons Io, Callisto, Europa, and Ganymede — now known as the Galilean Moons.

例如，1610 年，伽利略用第一台望远镜发现了木星的星木一、木四、木二和木，这些星现在被称为伽利略星。

" Jupiter's biggest moon is Ganymede, not Callisto, " she said, pointing over Ron's shoulder at a line in his Astronomy essay, " and it's lo that's got the volcanoes."

“木星最大的星是木，不是木四，”她从罗恩身后指着他那篇天学论中的一行字说，“有火山的应该是木一。”

The ESA took the opportunity to do a test run of Juice's instruments, which it will use to look for molecular signatures of habitability on the moons Europa, Ganymede and Callisto.

欧洲航天局借此机会对 Juice 的仪器进行了测试，这些仪器将用于寻找木二、木和木四上适宜居住的分子特征。