土星

2020年7月5日 Saturn’s Northern Hexagon Image Credit: NASA, ESA, JPL, SSI, Cassini Imaging Team Explanation: Why would clouds form a hexagon on Saturn? Nobody is sure. Originally discovered during the Voyager flybys of Saturn in the 1980s, nobody has ever seen anything like it anywhere else in the Solar System. Acquiring its first sunlit views of far northern Saturn in late 2012, the Cassini spacecraft’s wide-angle camera recorded this stunning, false-color image of the ringed planet’s north pole. The composite of near-infrared image data results in red hues for low clouds and green for high ones, giving the Saturnian cloudscape a vivid appearance. This and similar images show the stability of the hexagon even 20+ years after Voyager. Movies of Saturn’s North Pole show the cloud…

2020 June 20 Northern Summer on Titan Image Credit: Cassini Imaging Team, SSI, JPL, ESA, NASA Explanation: Today’s solstice brings summer to planet Earth’s northern hemisphere. But the northern summer solstice arrived for ringed planet Saturn over three years ago on May 24, 2017. Orbiting the gas giant, Saturn’s moon Titan experiences the Saturnian seasons. Larger than inner planet Mercury, Titan was captured in this Cassini spacecraft image about two weeks after its northern summer began. The near-infrared view finds bright methane clouds drifting through Titan’s dense, hazy atmosphere as seen from a distance of about 507,000 kilometers. Below the clouds, dark hydrocarbon lakes sprawl near its fully illuminated north pole. Tomorrow’s picture: Venus by moonlight 土卫六北半球的夏天 影像提供：Cassini Imaging Team, SSI, JPL, ESA, NASA 说明：明天的夏至将把夏天带到地球北半球，但对拥有行星环的土星而言，北半球的夏至降临在3年前的5月24日。而在绕行这颗气态巨行星的土卫六，也感受到土星的季节变化。这张呈现大于水星的土卫六的影像，是由卡西尼号太空船摄于土星夏季降临的2星期多之后。这张摄于约507，000公里之外的近红外光照片，记录了漂过土卫六致密雾霾天空的明亮甲烷云。在云层下方，可见到在阳光照耀的土卫六北极区，以及它附近广袤的暗色碳氢化合物湖泊。…

2020 May 27 Earth and Moon through Saturn’s Rings Image Credit: NASA, ESA, JPL-Caltech, SSI, Cassini Imaging Team; Processing & License: Kevin M. Gill Explanation: What are those dots between Saturn’s rings? Our Earth and Moon. Just over three years ago, because the Sun was temporarily blocked by the body of Saturn, the robotic Cassini spacecraft was able to look toward the inner Solar System. There, it spotted our Earth and Moon — just pin-pricks of light lying about 1.4 billion kilometers distant. Toward the right of the featured image is Saturn’s A ring, with the broad Encke Gap on the far right and the narrower Keeler Gap toward the center. On the far left is Saturn’s continually changing F Ring. From this perspective, the…

2020 April 19 Cassini Approaches Saturn Video Credit & Copyright: Cassini Imaging Team, ISS, JPL, ESA, NASA, S. Van Vuuren et al.; Music: Adagio for Strings (NY Philharmonic) Explanation: What would it look like to approach Saturn in a spaceship? One doesn’t have to just imagine — the Cassini spacecraft did just this in 2004, recording thousands of images along the way, and hundreds of thousands more since entering orbit. Some of Cassini’s early images have been digitally tweaked, cropped, and compiled into the featured inspiring video which is part of a larger developing IMAX movie project named In Saturn’s Rings. In the concluding sequence, Saturn looms increasingly large on approach as cloudy Titan swoops below. With Saturn whirling around in the background, Cassini is…

2020 March 30 The Colors of Saturn from Cassini Image Credit: NASA, ESA, JPL, ISS, Cassini Imaging Team; Processing & License: Judy Schmidt Explanation: What creates Saturn’s colors? The featured picture of Saturn only slightly exaggerates what a human would see if hovering close to the giant ringed world. The image was taken in 2005 by the robot Cassini spacecraft that orbited Saturn from 2004 to 2017. Here Saturn’s majestic rings appear directly only as a curved line, appearing brown, in part, from its infrared glow. The rings best show their complex structure in the dark shadows they create across the upper part of the planet. The northern hemisphere of Saturn can appear partly blue for the same reason that Earth’s skies can appear blue…

2020 March 20 Morning, Planets, Moon and Montreal Image Credit & Copyright: Arnaud Mariat Explanation: Dawn’s early light came to Montreal, northern planet Earth, on March 18, the day before the vernal equinox. At the end of that nearly equal night the Moon stands above a dense constellation of urban lights in this serene city and skyscape. Of course the Moon’s waning crescent faces toward the rising Sun. Skygazers could easily spot bright Jupiter just above the Moon, close on the sky to a fainter Mars. Saturn, a telescopic favorite, is just a pinprick of light below and farther left of the closer conjunction of Moon, Jupiter and Mars. Near the ecliptic, even Mercury is rising along a line extended to the horizon from Jupiter…

2020 March 16 A Moon Dressed Like Saturn Image Credit & Copyright: Francisco Sojuel Explanation: Why does Saturn appear so big? It doesn’t — what is pictured are foreground clouds on Earth crossing in front of the Moon. The Moon shows a slight crescent phase with most of its surface visible by reflected Earthlight known as ashen glow. The Sun directly illuminates the brightly lit lunar crescent from the bottom, which means that the Sun must be below the horizon and so the image was taken before sunrise. This double take-inducing picture was captured on 2019 December 24, two days before the Moon slid in front of the Sun to create a solar eclipse. In the foreground, lights from small Guatemalan towns are visible behind…

2019 December 29 Cassini Spacecraft Crosses Saturn’s Ring Plane Image Credit: NASA, ESA, JPL, ISS, Cassini Imaging Team; Processing: Fernando Garcia Navarro Explanation: If this is Saturn, where are the rings? When Saturn’s “appendages” disappeared in 1612, Galileo did not understand why. Later that century, it became understood that Saturn’s unusual protrusions were rings and that when the Earth crosses the ring plane, the edge-on rings will appear to disappear. This is because Saturn’s rings are confined to a plane many times thinner, in proportion, than a razor blade. In modern times, the robot Cassini spacecraft orbiting Saturn frequently crossed Saturn’s ring plane during its mission to Saturn, from 2004 to 2017. A series of plane crossing images from 2005 February was dug out of…

2019 November 3 Daphnis and the Rings of Saturn Image Credit: NASA, JPL-Caltech, Space Science Institute, Cassini Explanation: What’s happening to the rings of Saturn? A little moon making big waves. The moon is 8-kilometer Daphnis and it is making waves in the Keeler Gap of Saturn’s rings using just its gravity — as it bobs up and down, in and out. The featured image is a colored and more detailed version of a previously released images taken in 2017 by the robotic Cassini spacecraft during one of its Grand Finale orbits. Daphnis can be seen on the far right, sporting ridges likely accumulated from ring particles. Daphnis was discovered in Cassini images in 2005 and raised mounds of ring particles so high in 2009…