发射星云、暗星云与尘埃

发射星云、暗星云与尘埃

BySamuel Chan

2024年1月10日 The Light, the Dark, and the Dusty Image Credit & Copyright: Gábor Galambos Explanation: This colorful skyscape spans about three full moons across nebula rich starfields along the plane of our Milky Way Galaxy toward the royal northern constellation Cepheus. Near the edge of the region’s massive molecular cloud some 2,400 light-years away, bright reddish emission region Sharpless (Sh)2-155 is at the center of the frame, also known as the Cave Nebula. About 10 light-years across the cosmic cave’s bright walls of gas are ionized by ultraviolet light from the hot young stars around it. Dusty bluish reflection nebulae, like vdB 155 at the left, and dense obscuring clouds of dust also abound on the interstellar canvas. Astronomical explorations have revealed other dramatic signs…

雷神的头盔

雷神的头盔

BySamuel Chan

2024年1月9日 Thor’s Helmet Image Credit & Copyright: Ritesh Biswas Explanation: Thor not only has his own day (Thursday), but a helmet in the heavens. Popularly called Thor’s Helmet, NGC 2359 is a hat-shaped cosmic cloud with wing-like appendages. Heroically sized even for a Norse god, Thor’s Helmet is about 30 light-years across. In fact, the cosmic head-covering is more like an interstellar bubble, blown with a fast wind from the bright, massive star near the bubble’s center. Known as a Wolf-Rayet star, the central star is an extremely hot giant thought to be in a brief, pre-supernova stage of evolution. NGC 2359 is located about 15,000 light-years away toward the constellation of the Great Overdog. This remarkably sharp image is a mixed cocktail of data…

金星的位相

金星的位相

BySamuel Chan

2024年1月8日 The Phases of Venus Image Credit & License: Stéphane Gonzales Explanation: Venus goes through phases. Just like our Moon, Venus can appear as a full circular disk, a thin crescent, or anything in between. Venus, frequently the brightest object in the post-sunset or pre-sunrise sky, appears so small, however, that it usually requires binoculars or a small telescope to clearly see its current phase. The featured time-lapse sequence was taken over the course of six months in 2015 from Surgères, Charente-Maritime, France, and shows not only how Venus changes phase, but changes angular size as well. When Venus is on the far side of the Sun from the Earth, it appears angularly smallest and nearest to full phase, while when Venus and Earth are…

猫眼星云: 可见光及X射线波段的景观

猫眼星云: 可见光及X射线波段的景观

BySamuel Chan

2024年1月7日 The Cat’s Eye Nebula in Optical and X-ray Image Credit: NASA, ESA, Hubble Legacy Archive; Chandra X-ray Obs.; Processing & Copyright: Rudy Pohl Explanation: To some it looks like a cat’s eye. To others, perhaps like a giant cosmic conch shell. It is actually one of the brightest and most highly detailed planetary nebula known, composed of gas expelled in the brief yet glorious phase near the end of life of a Sun-like star. This nebula‘s dying central star may have produced the outer circular concentric shells by shrugging off outer layers in a series of regular convulsions. The formation of the beautiful, complex-yet-symmetric inner structures, however, is not well understood. The featured image is a composite of a digitally sharpened Hubble Space Telescope…

丘泽彗星的雪

丘泽彗星的雪

BySamuel Chan

2024年1月6日 The Snows of Churyumov-Gerasimenko Images Credit: ESA, Rosetta, MPS, OSIRIS; UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA; Animation: Jacint Roger Perez Explanation: You couldn’t really be caught in this blizzard while standing by a cliff on periodic comet 67P/Churyumov-Gerasimenko. Orbiting the comet in June of 2016, the Rosetta spacecraft’s narrow angle camera did record streaks of dust and ice particles similar to snow as they drifted across the field of view close to the camera and above the comet’s surface. Still, some of the bright specks in the scene are likely due to a rain of energetic charged particles or cosmic rays hitting the camera, and the dense background of stars in the direction of the constellation of the Big Dog (Canis Major). In the video, the background stars are…

四边形星群: 猎户座大星云的能量核心

四边形星群: 猎户座大星云的能量核心

BySamuel Chan

2024年1月5日 Trapezium: At the Heart of Orion Image Credit & Copyright: Fred Zimmer, Telescope Live Explanation: Near the center of this sharp cosmic portrait, at the heart of the Orion Nebula, are four hot, massive stars known as the Trapezium. Gathered within a region about 1.5 light-years in radius, they dominate the core of the dense Orion Nebula Star Cluster. Ultraviolet ionizing radiation from the Trapezium stars, mostly from the brightest star Theta-1 Orionis C powers the complex star forming region’s entire visible glow. About three million years old, the Orion Nebula Cluster was even more compact in its younger years and a dynamical study indicates that runaway stellar collisions at an earlier age may have formed a black hole with more than 100 times…

天市右垣十一: 速逃星

天市右垣十一: 速逃星

BySamuel Chan

2024年1月4日 Zeta Oph: Runaway Star Image Credit: NASA, JPL-Caltech, Spitzer Space Telescope Explanation: Like a ship plowing through cosmic seas, runaway star Zeta Ophiuchi produces the arcing interstellar bow wave or bow shock seen in this stunning infrared portrait. In the false-color view, bluish Zeta Oph, a star about 20 times more massive than the Sun, lies near the center of the frame, moving toward the left at 24 kilometers per second. Its strong stellar wind precedes it, compressing and heating the dusty interstellar material and shaping the curved shock front. What set this star in motion? Zeta Oph was likely once a member of a binary star system, its companion star was more massive and hence shorter lived. When the companion exploded as a…

新西兰上空的稳定极光红弧

新西兰上空的稳定极光红弧

BySamuel Chan

2024年1月3日 A SAR Arc from New Zealand Image Credit & Copyright: Tristian McDonald; Text: Tiffany Lewis (Michigan Tech U.) Explanation: What is that unusual red halo surrounding this aurora? It is a Stable Auroral Red (SAR) arc. SAR arcs are rare and have only been acknowledged and studied since 1954. The featured wide-angle photograph, capturing nearly an entire SAR arc surrounding more common green and red aurora, was taken earlier this month from Poolburn, New Zealand, during an especially energetic geomagnetic storm. Why SAR arcs form remains a topic of research, but is likely related to Earth’s protective magnetic field, a field created by molten iron flowing deep inside the Earth. This magnetic field usually redirects incoming charged particles from the Sun’s wind toward the…

火箭凌越波纹月

火箭凌越波纹月

BySamuel Chan

2024年1月2日 Rocket Transits Rippling Moon Image Credit & Copyright: Steven Madow Explanation: Can a rocket make the Moon ripple? No, but it can make a background moon appear wavy. The rocket, in this case, was a SpaceX Falcon Heavy that blasted off from NASA‘s Kennedy Space Center last week. In the featured launch picture, the rocket’s exhaust plume glows beyond its projection onto the distant, rising, and nearly full moon. Oddly, the Moon’s lower edge shows unusual drip-like ripples. The Moon itself, far in the distance, was really unchanged. The physical cause of these apparent ripples was pockets of relatively hot or rarefied air deflecting moonlight less strongly than pockets of relatively cool or compressed air: refraction. Although the shot was planned, the timing of…

NGC 1232: 宏伟的螺旋星系

NGC 1232: 宏伟的螺旋星系

BySamuel Chan

2024年1月1日 NGC 1232: A Grand Design Spiral Galaxy Image Credit: FORS, 8.2-meter VLT Antu, ESO Explanation: Galaxies are fascinating not only for what is visible, but for what is invisible. Grand spiral galaxy NGC 1232, captured in detail by one of the Very Large Telescopes, is a good example. The visible is dominated by millions of bright stars and dark dust, caught up in a gravitational swirl of spiral arms revolving about the center. Open clusters containing bright blue stars can be seen sprinkled along these spiral arms, while dark lanes of dense interstellar dust can be seen sprinkled between them. Less visible, but detectable, are billions of dim normal stars and vast tracts of interstellar gas, together wielding such high mass that they dominate…