In 1781, German-born British astronomer William Herschel made Uranus the first planet discovered with a telescope. 1781年，德国出生的英国天文学家威廉·赫歇尔让天王星成为了第一颗用望远镜发现的行星。 But, 243 years later, we still do not know much about this cold planet, the third largest in our solar system.但是，243年后，我们仍然对这颗寒冷的行星知之甚少，它是我们太阳系的第三大行星。 And some of what we thought we knew about it turns out to be untrue.而我们原本以为自己知道的某些事情，后来被证明是错的。 Much of the knowledge about Uranus was collected when NASA's robotic spacecraft Voyager 2 flew past it in 1986.关于天王星的许多知识都源于1986年NASA的旅行者2号机器人航天器经过它时收集的信息。 But scientists have since learned that the craft visited at a time of unusual conditions.但科学家们后来了解到，这艘飞船造访时情况很特殊。 An intense solar wind event at the time led to misleading observations about Uranus, and especially its magnetic field.当时强烈的太阳风事件导致了对天王星的误导性观测，特别是它的磁场。 The solar wind is a high speed flow of charged particles coming from the sun.太阳风是来自太阳的高速带电粒子流。 The researchers took a second look at eight months of data from around the time of Voyager two's visit and found that it flew near Uranus just a few days after the solar wind had reduced the planet's magnetosphere to about 20 percent of its usual size.研究人员重新研究了旅行者2号访问天王星前后8个月的数据，发现就在太阳风将天王星的磁层缩小到正常大小的20%后几天，它就飞到了天王星附近。 A magnetosphere is an area of space surrounding a planet that is controlled by the planet's magnetic field.磁层是由行星磁场控制的围绕行星的空间区域。 The magnetosphere protects the planet from solar and cosmic particle radiation.磁层保护行星免受太阳和宇宙粒子辐射的影响。 The Voyager 2 observations led scientists to think Uranus' magnetosphere lacked in plasma and had very intense belts of highly energetic electrons.旅行者2号的观测让科学家们认为天王星的磁层缺乏等离子体，并且有非常强烈的高能电子带。 Plasma is often called the fourth state of matter after solids, liquids and gases.等离子体通常被称为继固体、液体和气体之后的第四种物质状态。 In the night sky, plasma gives out light in the form of stars, nebulas, and even the auroras above the north and south poles.在夜空中，等离子体以恒星、星云甚至北极和南极上方的极光的形式发出光。 Plasma is a common feature in the magnetosphere of other planets, so scientists did not understand why there would not be much of it observed around Uranus.等离子体是其他行星磁层中的常见特征，因此科学家们不明白为什么天王星周围没有观测到太多等离子体。 Jamie Jasinski studies space plasma at NASA's Jet Propulsion Laboratory.杰米·贾辛斯基在NASA的喷气推进实验室研究太空等离子体。 He is the lead writer of the study published recently in the publication Nature Astronomy.他是最近发表在《自然·天文学》杂志上的这项研究的主要作者。 "We found that the solar wind conditions present during the flyby only occur 4 percent of the time.“我们发现，在飞越过程中出现太阳风的情况只有4%的几率。 The flyby occurred during the maximum peak solar wind intensity in that entire eight-month period," Jasinski said.这次飞越发生在整个8个月期间太阳风强度最大的时候。”贾辛斯基说。 "We would have observed a much bigger magnetosphere if Voyager 2 had arrived a week earlier."“如果旅行者2号早一周到达，就会观测到一个更大的磁层。” Such a visit would likely have shown that the Uranus magnetosphere is like those of Jupiter, Saturn and Neptune, the solar system's other large planets, the researchers said.研究人员说，这种情况下的访问可能会显示天王星的磁层与太阳系的其他大型行星木星、土星和海王星的磁层相似。 Uranus looks blue green because of the methane contained in its atmosphere.天王星看起来是蓝绿色的，因为它的大气层中含有甲烷。 The planet is big enough to fit 63 Earths inside it.这颗行星的大小足以容纳63个地球。 Among the solar system's eight planets, only Jupiter and Saturn are larger.在太阳系的八颗行星中，只有木星和土星比天王星大。 Uranus orbits almost 20 times further from the sun than Earth does.天王星的轨道距离太阳的距离几乎是地球的20倍。 And it has 28 known moons and two sets of rings.它有28颗已知卫星和两组光环。 Data collected by Voyager 2 had suggested that its two largest moons - Titania and Oberon - often orbit outside the magnetosphere.旅行者2号收集的数据表明，它的两颗最大的卫星--天卫三和天卫四--经常在磁层之外运行。 But the new study shows that they usually stay inside the protective space, making it easier for scientists to magnetically detect possible subsurface oceans.但新的研究表明，它们通常呆在保护空间内，这使得科学家更容易用磁场探测到可能存在的地下海洋。 "Both are thought to be prime candidates for hosting liquid water oceans in the Uranian system...," Jet Propulsion Laboratory planetary scientist and study co-writer Corey Cochrane said.喷气推进实验室的行星科学家和研究合著者科里·科克伦说：“这两颗行星都被认为是在天王星系统…中容纳液态水海洋的主要候选者。” Scientists want to learn whether subsurface oceans on moons in the outer solar system have conditions that could support life.科学家们想了解外太阳系卫星上的地下海洋是否具备支持生命存在的条件。 So, on October 14, NASA launched a spacecraft on a mission to Jupiter's moon Europa to try to answer that question.因此，10月14日，NASA发射了一艘航天器，前往木星的卫星木卫二，试图回答这个问题。 "A future mission to Uranus is crucial to understanding not only the planet and magnetosphere, but also its atmosphere, rings and moons," Jasinski said.贾辛斯基说：“未来前往天王星的任务不仅对了解这颗行星和磁层，而且对了解它的大气层、光环和卫星都是至关重要的。” I'm Caty Weaver.凯蒂·韦弗为您播报。
