土星环后方的卫星

土星环后方的卫星

ByNASA中文

2022年1月4日 Moons Beyond Rings at Saturn Image Credit: NASA, ESA, JPL, Cassini Imaging Team Explanation: What’s happened to that moon of Saturn? Nothing — Saturn’s moon Rhea is just partly hidden behind Saturn’s rings. In 2010, the robotic Cassini spacecraft then orbiting Saturn took this narrow-angle view looking across the Solar System’s most famous rings. Rings visible in the foreground include the thin F ring on the outside and the much wider A and B rings just interior to it. Although it seems to be hovering over the rings, Saturn’s moon Janus is actually far behind them. Janus is one of Saturn’s smaller moons and measures only about 180 kilometers across. Farther out from the camera is the heavily cratered Rhea, a much larger moon…

李奥纳德彗星的长尾

李奥纳德彗星的长尾

ByNASA中文

2022年1月3日 Comet Leonard’s Long Tail Image Credit & Copyright: Jan Hattenbach Explanation: You couldn’t see Comet Leonard’s extremely long tail with a telescope — it was just too long. You also couldn’t see it with binoculars — still too long. Or with your eyes — it was too dim. Or from a city — the sky was too bright. But from a dark location with a low horizon — your camera could. And still might — if the comet survives today’s closest encounter with the Sun, which occurs between the orbits of Mercury and Venus. The featured picture was created from two deep and wide-angle camera images taken from La Palma in the Canary Islands of Spain late last month. Afterwards, if it survives, what…

寒冬道路上空的四重月晕

寒冬道路上空的四重月晕

ByNASA中文

2022年1月2日 Quadruple Lunar Halo Over Winter Road Image Credit & Copyright: Dani Caxete Explanation: Sometimes falling ice crystals make the atmosphere into a giant lens causing arcs and halos to appear around the Sun or Moon. One Saturday night in 2012 was just such a time near Madrid, Spain, where a winter sky displayed not only a bright Moon but four rare lunar halos. The brightest object, near the top of the featured image, is the Moon. Light from the Moon refracts through tumbling hexagonal ice crystals into a somewhat rare 22-degree halo seen surrounding the Moon. Elongating the 22-degree arc horizontally is a more rare circumscribed halo caused by column ice crystals. Even more rare, some moonlight refracts through more distant tumbling ice crystals…

2021年的满月

2021年的满月

ByNASA中文

2022年1月1日 The Full Moon of 2021 Image Credit & Copyright: Soumyadeep Mukherjee Explanation: Every Full Moon of 2021 shines in this year-spanning astrophoto project, a composite portrait of the familiar lunar nearside at each brightest lunar phase. Arranged by moonth, the year progresses in stripes beginning at the top. Taken with the same camera and lens the stripes are from Full Moon images all combined at the same pixel scale. The stripes still looked mismatched, but they show that the Full Moon’s angular size changes throughout the year depending on its distance from Kolkata, India, planet Earth. The calendar month, a full moon name, distance in kilometers, and angular size is indicated for each stripe. Angular size is given in minutes of arc corresponding to…

前往L2点途中的詹姆斯·韦伯太空望远镜

前往L2点途中的詹姆斯·韦伯太空望远镜

ByNASA中文

2021年12月31日 JWST on the Road to L2 Image Credit & Copyright: Malcolm Park (North York Astronomical Association) Explanation: This timelapse gif tracks the James Webb Space Telescope as it streaks across the stars of Orion on its journey to a destination beyond the Moon. Recorded on December 28, 12 consecutive exposures each 10 minutes long were aligned and combined with a subsequent color image of the background stars to create the animation. About 2.5 days after its December 25 launch, JWST cruised past the altitude of the Moon’s orbit as it climbed up the gravity ridge from Earth to reach a halo orbit around L2, an Earth-Sun Lagrange point. Lagrange points are convenient locations in space where the combined gravitational attraction of one massive body…

李奥纳德彗星的超长彗尾

李奥纳德彗星的超长彗尾

ByNASA中文

2021年12月30日 The Further Tail of Comet Leonard Image Credit & Copyright: Daniele Gasparri Explanation: Comet Leonard, brightest comet of 2021, is at the lower left of these two panels captured on December 29 in dark Atacama desert skies. Heading for its perihelion on January 3 Comet Leonard’s visible tail has grown. Stacked exposures with a wide angle lens (also displayed in a reversed B/W scheme for contrast), trace the complicated ion tail for an amazing 60 degrees, with bright Jupiter shining near the horizon at lower right. Material vaporizing from Comet Leonard’s nucleus, a mass of dust, rock, and ices about 1 kilometer across, has produced the long tail of ionized gas fluorescing in the sunlight. Likely flares on the comet’s nucleus and buffeting by…

木星的巨风暴与高层云

木星的巨风暴与高层云

ByNASA中文

2021年12月29日 Giant Storms and High Clouds on Jupiter Image Credit: NASA/JPL-Caltech/SwRI/MSSS; Processing & License: Kevin M. Gill Explanation: What and where are these large ovals? They are rotating storm clouds on Jupiter imaged last month by NASA’s Juno spacecraft. In general, higher clouds are lighter in color, and the lightest clouds visible are the relatively small clouds that dot the lower oval. At 50 kilometers across, however, even these light clouds are not small. They are so high up that they cast shadows on the swirling oval below. The featured image has been processed to enhance color and contrast. Large ovals are usually regions of high pressure that span over 1000 kilometers and can last for years. The largest oval on Jupiter is the Great…

瑞典上空的日晕

瑞典上空的日晕

ByNASA中文

2021年12月28日 Sun Halo over Sweden Video Credit & Copyright: Håkan Hammar (Vemdalen Ski Resort, SkiStar) Explanation: What’s happened to the Sun? Sometimes it looks like the Sun is being viewed through a giant lens. In the featured video, however, there are actually millions of tiny lenses: ice crystals. Water may freeze in the atmosphere into small, flat, six-sided, ice crystals. As these crystals flutter to the ground, much time is spent with their faces flat and parallel to the ground. An observer may find themselves in the same plane as many of the falling ice crystals near sunrise or sunset. During this alignment, each crystal can act like a miniature lens, refracting sunlight into our view and creating phenomena like parhelia, the technical term for…

詹姆斯·韦伯太空望远镜发射烟尘后方的李奥纳德彗星

詹姆斯·韦伯太空望远镜发射烟尘后方的李奥纳德彗星

ByNASA中文

2021年12月27日 Comet Leonard behind JWST Launch Plume Image Credit & Copyright: Matipon Tangmatitham (NARIT) Explanation: Which one of these two streaks is a comet? Although they both have comet-like features, the lower streak is the only real comet. This lower streak shows the coma and tail of Comet Leonard, a city-sized block of rocky ice that is passing through the inner Solar System as it continues its looping orbit around the Sun. Comet Leonard has recently passed its closest to both the Earth and Venus and will round the Sun next week. The comet, still visible to the unaided eye, has developed a long and changing tail in recent weeks. In contrast, the upper streak is the launch plume of the Ariane V rocket that…

地球上空的詹姆斯·韦伯太空望远镜

地球上空的詹姆斯·韦伯太空望远镜

ByNASA中文

2021年12月26日 James Webb Space Telescope over Earth Image Credit: Arianespace, ESA, NASA, CSA, CNES Explanation: There’s a big new telescope in space. This one, the James Webb Space Telescope (JWST), not only has a mirror over five times larger than Hubble’s in area, but can see better in infrared light. The featured picture shows JWST high above the Earth just after being released by the upper stage of an Ariane V rocket, launched yesterday from French Guiana. Over the next month, JWST will move out near the Sun-Earth L2 point where it will co-orbit the Sun with the Earth. During this time and for the next five months, JWST will unravel its segmented mirror and an array of sophisticated scientific instruments — and test them….