NEOWISE彗星

2020年8月12日 The Shifting Tails of Comet NEOWISE Image Credit & Copyright: Ignacio Llorens Explanation: Keep your eye on the ion tail of Comet NEOWISE. A tale of this tail is the trail of the Earth. As with all comets, the blue ion tail always points away from the Sun. But as Comet C/2020 F3 (NEOWISE) rounded our Sun, its ion tail pointed in slightly different directions. This is because between 2020 July 17 and July 25 when the featured images were taken, the Earth moved noticeably in its orbit around the Sun. But the Earth’s motion made the Sun appear to shift in the sky. So even though you can’t see the Sun directly in the featured image(s), the directions of the ion tails reveal…

2020年8月3日 Comet NEOWISE over Vikos Gorge Image Credit & Copyright: Constantine Emmanouilidi Explanation: Did the Earth part to show us this comet? Of course not, even if this image makes it seem that way. Pictured far in the background is Comet NEOWISE as it appeared about two weeks ago over northern Greece. Above the comet are many stars including the bright stars of the Big Dipper (also the Sorcerer, in Aztec mythology), an asterism that many people around the world used to find the naked-eye comet as it hovered in the northern sky over the past month. In the foreground is Vikos Gorge, the deepest gorge on Earth, relative to its width. The gorge was slowly created by erosion from the Voidomatis River over the…

2020年7月27日 Comet and Lightning Beyond Bighorn Mountains Image Credit & Copyright: Kevin Palmer Explanation: Normally, Steamboat Point looks cool — but not this cool. Every day, the iconic peak of the Bighorn Mountains is an interesting sight, in particular from US Highway 14 in Wyoming. On some rare days, the rocky vertical ridges look even more incredible when seen in front of a distant lightning storm. Earlier this month, though, something even more unusual happened — the naked-eye Comet NEOWISE rose above it in the middle of the night. Just as a distant lightning storm was occurring in the background. Recognizing a rare opportunity, a determined astrophotographer spent a sleepless night capturing over 1400 images of this unusual triple conjunction. The featured image is among…

2020年7月22日 The Structured Tails of Comet NEOWISE Image Credit & Copyright: Zixuan Lin (Beijing Normal U.) Explanation: What is creating the structure in Comet NEOWISE’s tails? Of the two tails evident, the blue ion tail on the left points directly away from the Sun and is pushed out by the flowing and charged solar wind. Structure in the ion tail comes from different rates of expelled blue-glowing ions from the comet’s nucleus, as well as the always complex and continually changing structure of our Sun’s wind. Most unusual for Comet C/2020 F3 (NEOWISE), though, is the wavy structure of its dust tail. This dust tail is pushed out by sunlight, but curves as heavier dust particles are better able to resist this light pressure and…

2020年7月20日 Comet NEOWISE and Nebulae Image Credit & Copyright: Jarek Oszywa Explanation: Would you brave wild animals to photograph this sky? One astrophotographer did — and we all get to reap the rewards. First, thousands of stars were visible with many of the brightest impressively blue. Next, several red-glowing nebulae were discernible, including the California Nebula on the far right, and, above it, the Heart and Soul nebulae. But the real reason to brave the local wildlife was Comet NEOWISE, visible on the left. In the featured long-duration composite taken last week, Comet NEOWISE’s blue-glowing ion tail points straight up, away from the rising Sun, while the Sun-reflecting dust tail trails off toward the right. The picture combines three exposures taken consecutively over 10 minutes…