朱诺号影像: 木卫三

朱诺号影像: 木卫三

ByNASA中文

2023年11月28日 Ganymede from Juno Image Credit & Copyright: NASA/JPL-Caltech/SwRI/MSSS; Processing & License: Kevin M. Gill; Explanation: What does the largest moon in the Solar System look like? Jupiter‘s moon Ganymede, larger than even Mercury and Pluto, has an icy surface speckled with bright young craters overlying a mixture of older, darker, more cratered terrain laced with grooves and ridges. The cause of the grooved terrain remains a topic of research, with a leading hypothesis relating it to shifting ice plates. Ganymede is thought to have an ocean layer that contains more water than Earth — and might contain life. Like Earth’s Moon, Ganymede keeps the same face towards its central planet, in this case Jupiter. The featured image was captured in 2021 by NASA’s robotic…

木卫三阴影中的木星

木卫三阴影中的木星

ByNASA中文

During its 40th close pass by Jupiter, our Juno spacecraft saw Ganymede cast a large, dark spot on the planet on Feb. 25, 2022. JunoCam captured this image from very close to Jupiter, making Ganymede’s shadow appear especially large. At the time the raw image was taken, the Juno spacecraft was about 44,000 miles (71,000 kilometers) above Jupiter’s cloud tops and 15 times closer to the planet than Ganymede. An observer at Jupiter’s cloud tops within the oval shadow would experience a total eclipse of the Sun. Total eclipses are more common on Jupiter than Earth for several reasons: Jupiter has four major moons (Ganymede, Io, Callisto, and Europa) that often pass between Jupiter and the Sun, and since Jupiter’s moons orbit in a plane…

木卫三的影子之下

木卫三的影子之下

ByNASA中文

2022年10月7日 In Ganymede’s Shadow Image Credit & Copyright: Andrew McCarthy Explanation: At opposition, opposite the Sun in Earth’s sky, late last month Jupiter is also approaching perihelion, the closest point to the Sun in its elliptical orbit, early next year. That makes Jupiter exceptionally close to our fair planet, currently resulting in excellent views of the Solar System’s ruling gas giant. On September 27, this sharp image of Jupiter was recorded with a small telescope from a backyard in Florence, Arizona. The stacked video frames reveal the massive world bounded by planet girdling winds. Dark belts and light zones span the gas giant, along with rotating oval storms and its signature Great Red Spot. Galilean moon Ganymede is below and right in the frame. The…

木星上的卫星影子

木星上的卫星影子

ByNASA中文

2022年4月27日 Moon Shadow on Jupiter Image Credit: NASA/JPL-Caltech/SwRI/MSSS; Processing & License: Thomas Thomopoulos Explanation: What is that large dark spot on Jupiter? It’s the shadow of Ganymede, Jupiter’s largest moon. When Jupiter’s moons cross between the Jovian giant and the Sun, they created shadows just like when the Earth’s moon crosses between the Earth and the Sun. Also like on Earth, if you were in a dark shadow on Jupiter, you would see a moon completely eclipse the Sun. Unlike on Earth, moon shadows occur most days on Jupiter — what’s more unusual is that a spacecraft was close enough to record one with a high-resolution image. That spacecraft, Juno, was passing so close to Jupiter in late February that nearby clouds and the dark…

朱诺号飞越木卫三和木星

朱诺号飞越木卫三和木星

ByNASA中文

2021年10月11日 Juno Flyby of Ganymede and Jupiter Video Credit: Images: NASA, JPL-Caltech, SWRI, MSSS; Animation: Koji Kuramura, Gerald Eichstädt, Mike Stetson; Music: Vangelis Explanation: What would it be like to fly over the largest moon in the Solar System? In June, the robotic Juno spacecraft flew past Jupiter’s huge moon Ganymede and took images that have been digitally constructed into a detailed flyby. As the featured video begins, Juno swoops over the two-toned surface of the 2,000-km wide moon, revealing an icy alien landscape filled with grooves and craters. The grooves are likely caused by shifting surface plates, while the craters are caused by violent impacts. Continuing on in its orbit, Juno then performed its 34th close pass over Jupiter’s clouds. The digitally-constructed video shows…

三星凌木及交食

三星凌木及交食

ByNASA中文

2021年8月21日 Triple Transit and Mutual Events Image Credit & Copyright: Christopher Go Explanation: These three panels feature the Solar System’s ruling gas giant Jupiter on August 15 as seen from Cebu City, Philippines, planet Earth. On that date the well-timed telescopic views detail some remarkable performances, transits and mutual events, by Jupiter’s Galilean moons. In the top panel, Io is just disappearing into Jupiter’s shadow at the far right, but the three other large Jovian moons appear against the planet’s banded disk. Brighter Europa and darker Ganymede are at the far left, also casting their two shadows on the gas giant’s cloud tops. Callisto is below and right near the planet’s edge, the three moons in a triple transit across the face of Jupiter. Moving…

哈勃太空望远镜在木卫三中发现水蒸气的第一个证据

哈勃太空望远镜在木卫三中发现水蒸气的第一个证据

ByNASA中文

天文学家首次在木星的卫星木卫三的大气中发现了水蒸气的证据。这种水蒸气是在木卫三表面的冰升华时形成的，也就是说，从固体变成气体。 科学家们利用NASA哈勃太空望远镜新的档案数据集，做出了这一发现，发表在《自然天文学》杂志上。 这张照片展示了1996年NASA哈勃太空望远镜观测到的木星卫星木卫三。木卫三位于5亿英里(超过6亿公里)之外，哈勃可以跟踪卫星上的变化，并在紫外和近红外波长揭示其他特征。天文学家现在利用哈勃望远镜提供的新的档案数据集，首次揭示了木星卫星木卫三大气中存在水蒸气的证据，这是由于水蒸气从卫星的冰面热逸出而来。 影像来源：NASA, ESA, John Spencer (SwRI Boulder) 此前的研究提供了间接证据，表明太阳系最大的卫星木卫三含有的水比地球上所有的海洋都要多。然而，那里的温度非常低，表面的水被冻结成固体。木卫三的海洋位于地壳以下约100英里处；因此，水汽并不代表这片海洋的蒸发。 天文学家重新审视了过去20年的哈勃观测数据，发现了这个水蒸气的证据。 1998年，哈勃太空望远镜成像光谱仪首次拍摄了木卫三的紫外线图像，显示了被称为极光带的带电气体的彩色条带，并提供了进一步的证据，证明木卫三具有弱磁场。 这些紫外观察的相似性可以用分子氧(O2)的存在来解释。但一些观测到的特征与纯氧大气的预期排放不符。与此同时，科学家得出结论，这种差异可能与氧原子(O)浓度较高有关。 作为支持NASA2018年朱诺任务的大型观测项目的一部分，瑞典斯德哥尔摩KTH皇家理工学院的洛伦兹·罗斯（Lorenz Roth）领导的团队开始用哈勃望远镜测量原子氧的含量。该团队的分析结合了两个仪器的数据：2018年哈勃的宇宙起源光谱仪和1998至2010年太空望远镜成像光谱仪（STIS）的存档图像。 令他们惊讶的是，与最初对1998年数据的解释相反，他们发现在木卫三的大气层中几乎没有任何原子氧。这意味着对于这些紫外极光图像中的明显差异，一定有另一种解释。 罗斯和他的团队随后进一步观察了紫外线图像中极光的相对分布。木卫三的表面温度在一天中变化强烈，在赤道附近的中午，它可能变得足够温暖，以至于冰面释放（或升华）一些少量水分子。事实上，紫外线图像中感知到的差异与木卫三大气中可能存在的水的位置直接相关。 1998年，哈勃太空望远镜成像光谱仪拍摄了木卫三的第一批紫外线图像，揭示了观测到的木卫三大气层排放物的一种特殊模式。卫星上的极光带与地球和其他有磁场的行星上观测到的极光椭圆形有点相似。这是木卫三有永久磁场的证据。紫外线观测中的相似之处被解释为分子氧的存在。这种差异当时被解释为原子氧的存在，它产生的信号对一种紫外线颜色的影响要大于另一种。 影像来源：NASA, ESA, Lorenz Roth (KTH) “到目前为止，只有分子氧被观察到，”罗斯解释说。“这是带电粒子侵蚀冰表面时产生的。我们现在测量的水蒸气来自于冰的升华，由水蒸气从温暖的冰区热逃逸引起。” 这一发现为欧空局（European Space Agency）即将开展的任务JUICE（JUpiter ICy moons Explorer的缩写）增添了期待。JUICE是欧空局2015-2025年宇宙愿景计划中的第一个大型任务。计划于2022年发射，2029年抵达木星，它将用至少三年的时间对木星及其最大的三颗卫星进行详细观测，特别是调查木卫三作为一个行星体是否是潜在的栖息地。 木卫三被确定为详细调查的对象，因为它为分析一般冰雪世界的性质、演变和潜在的可居住性提供了一个天然的实验室，它在伽利略卫星系统中发挥的作用，以及它与木星及其环境的独特磁和等离子体相互作用。 罗斯补充说:“我们的结果可以为JUICE仪器团队提供有价值的信息，这些信息可能被用来完善他们的观测计划，以优化航天器的使用。” 现在，NASA的朱诺号任务正在仔细观察木卫三，并于最近发布了这颗冰冷卫星的新图像。自2016年以来，朱诺号一直在研究木星及其环境，也被称为木星系。 天文学家利用美国宇航局哈勃太空望远镜的新数据和档案数据集，发现了木星的卫星木卫三大气层中的水蒸气证据。水蒸气的存在是由于来自卫星冰面的水分子的热激发。以前的研究已经提供了间接的证据，证明木卫三上的水比地球上所有的海洋都多。然而，那里的温度是如此之低，以至于表面的水会冻结，海洋大约位于地壳以下100英里。 视频来源：NASA’s Goddard Space Flight Center 了解木星系并阐明它的历史，从它的起源到可能出现的宜居环境，将使我们更好地了解气态巨行星及其卫星如何形成和演变。此外，还有望在类似木星的系外行星系统的可居住性方面有新的认识。 哈勃太空望远镜是NASA和ESA之间的一个国际合作项目。位于马里兰州格林贝尔特的NASA戈达德太空飞行中心负责管理该望远镜。位于马里兰州巴尔的摩市的太空望远镜科学研究所（STScI）负责哈勃望远镜的科学操作。STScI由位于华盛顿特区的天文学研究大学协会为NASA运营。 参考来源： https://www.nasa.gov/feature/goddard/2021/hubble-finds-first-evidence-of-water-vapor-at-jupiter-s-moon-ganymede

朱诺号影像：木卫三

朱诺号影像：木卫三

ByNASA中文

2021年06月14日 Ganymede from Juno Image Credit: NASA/JPL-Caltech/SwRI/MSSS; Processing & License: Kevin M. Gill; Explanation: What does the largest moon in the Solar System look like? Jupiter’s moon Ganymede, larger than even Mercury and Pluto, has an icy surface speckled with bright young craters overlying a mixture of older, darker, more cratered terrain laced with grooves and ridges. The cause of the grooved terrain remains a topic of research, with a leading hypothesis relating it to shifting ice plates. Ganymede is thought to have an ocean layer that contains more water than Earth — and might contain life. Like Earth’s Moon, Ganymede keeps the same face towards its central planet, in this case Jupiter. The featured image was captured last week by NASA’s robotic Juno spacecraft…