MyCn 18: 沙漏星云

MyCn 18: 沙漏星云

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2023年10月3日 MyCn 18: The Engraved Hourglass Planetary Nebula Image Credit & Copyright: NASA, ESA, Hubble, HLA; Processing & Copyright: Harshwardhan Pathak Explanation: Do you see the hourglass shape — or does it see you? If you can picture it, the rings of MyCn 18 trace the outline of an hourglass — although one with an unusual eye in its center. Either way, the sands of time are running out for the central star of this hourglass-shaped planetary nebula. With its nuclear fuel exhausted, this brief, spectacular, closing phase of a Sun-like star’s life occurs as its outer layers are ejected – its core becoming a cooling, fading white dwarf. In 1995, astronomers used the Hubble Space Telescope (HST) to make a series of images of…

NGC 1360：知更鸟蛋星云

NGC 1360：知更鸟蛋星云

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2023年8月5日 NGC 1360: The Robin’s Egg Nebula Image Credit & Copyright: Dong Liang Explanation: This pretty nebula lies some 1,500 light-years away, its shape and color in this telescopic view reminiscent of a robin’s egg. The cosmic cloud spans about 3 light-years, nestled securely within the boundaries of the southern constellation Fornax. Recognized as a planetary nebula, egg-shaped NGC 1360 doesn’t represent a beginning though. Instead it corresponds to a brief and final phase in the evolution of an aging star. In fact, visible at the center of the nebula, the central star of NGC 1360 is known to be a binary star system likely consisting of two evolved white dwarf stars, less massive but much hotter than the Sun. Their intense and otherwise invisible…

M15: 紧实的球状星团

M15: 紧实的球状星团

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2023年6月15日 M15: Dense Globular Star Cluster Image Credit: NASA, ESA, Hubble Legacy Archive; Processing: Ehsan Ebrahimian Explanation: Messier 15 is an immense swarm of over 100,000 stars. A 13 billion year old relic of the early formative years of our galaxy it’s one of about 170 globular star clusters that still roam the halo of the Milky Way. Centered in this sharp reprocessed Hubble image, M15 lies some 35,000 light-years away toward the constellation Pegasus. Its diameter is about 200 light-years, but more than half its stars are packed into the central 10 light-years or so, making one of the densest concentrations of stars known. Hubble-based measurements of the increasing velocities of M15’s central stars are evidence that a massive black hole resides at the…

M27: 哑铃星云

M27: 哑铃星云

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2023年5月30日 M27: The Dumbbell Nebula Image Credit & Copyright: Patrick A. Cosgrove Explanation: Is this what will become of our Sun? Quite possibly. The first hint of our Sun‘s future was discovered inadvertently in 1764. At that time, Charles Messier was compiling a list of diffuse objects not to be confused with comets. The 27th object on Messier’s list, now known as M27 or the Dumbbell Nebula, is a planetary nebula, one of the brightest planetary nebulae on the sky and visible with binoculars toward the constellation of the Fox (Vulpecula). It takes light about 1000 years to reach us from M27, featured here in colors emitted by sulfur (red), hydrogen (green) and oxygen (blue). We now know that in about 6 billion years, our…

猫眼星云的大视野深场影像

猫眼星云的大视野深场影像

ByNASA中文

2023年5月25日 Cat’s Eye Wide and Deep Image Credit & Copyright: Jean-François Bax, Guillaume Gruntz Explanation: The Cat’s Eye Nebula (NGC 6543) is one of the best known planetary nebulae in the sky. Its more familiar outlines are seen in the brighter central region of the nebula in this impressive wide-angle view. But this wide and deep image combining data from two telescopes also reveals its extremely faint outer halo. At an estimated distance of 3,000 light-years, the faint outer halo is over 5 light-years across. Planetary nebulae have long been appreciated as a final phase in the life of a sun-like star. More recently, some planetary nebulae are found to have halos like this one, likely formed of material shrugged off during earlier episodes in…

加法夏望远镜的螺旋星云

加法夏望远镜的螺旋星云

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2023年5月7日 The Helix Nebula from CFHT Image Credit: CFHT, Coelum, MegaCam, J.-C. Cuillandre (CFHT) & G. A. Anselmi (Coelum) Explanation: Will our Sun look like this one day? The Helix Nebula is one of brightest and closest examples of a planetary nebula, a gas cloud created at the end of the life of a Sun-like star. The outer gasses of the star expelled into space appear from our vantage point as if we are looking down a helix. The remnant central stellar core, destined to become a white dwarf star, glows in light so energetic it causes the previously expelled gas to fluoresce. The Helix Nebula, given a technical designation of NGC 7293, lies about 700 light-years away towards the constellation of the Water Bearer…

M2-9: 蝴蝶星云的翅膀

M2-9: 蝴蝶星云的翅膀

ByNASA中文

2023年4月16日 M2-9: Wings of a Butterfly Nebula Image Credit: Hubble Legacy Archive, NASA, ESA; Processing: Judy Schmidt Explanation: Are stars better appreciated for their art after they die? Actually, stars usually create their most artistic displays as they die. In the case of low-mass stars like our Sun and M2-9 pictured here, the stars transform themselves from normal stars to white dwarfs by casting off their outer gaseous envelopes. The expended gas frequently forms an impressive display called a planetary nebula that fades gradually over thousands of years. M2-9, a butterfly planetary nebula 2100 light-years away shown in representative colors, has wings that tell a strange but incomplete tale. In the center, two stars orbit inside a gaseous disk 10 times the orbit of Pluto….

银河中心的电波弧

银河中心的电波弧

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2023年4月3日 The Galactic Center Radio Arc Image Credit: Ian Heywood (Oxford U.), SARAO; Explanation: What causes this unusual curving structure near the center of our Galaxy? The long parallel rays slanting across the top of the featured radio image are known collectively as the Galactic Center Radio Arc and point out from the Galactic plane. The Radio Arc is connected to the Galactic Center by strange curving filaments known as the Arches. The bright radio structure at the bottom right surrounds a black hole at the Galactic Center and is known as Sagittarius A*. One origin hypothesis holds that the Radio Arc and the Arches have their geometry because they contain hot plasma flowing along lines of a constant magnetic field. Images from NASA’s Chandra…

哈勃影像: 环状星云M57

哈勃影像: 环状星云M57

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2023年4月2日 M57: The Ring Nebula from Hubble Image Credit: NASA, ESA, Hubble Legacy Archive; Processing: Judy Schmidt Explanation: It was noticed hundreds of years ago by stargazers who could not understand its unusual shape. It looked like a ring on the sky. Except for the rings of Saturn, the Ring Nebula (M57) may be the most famous celestial circle. We now know what it is, and that its iconic shape is due to our lucky perspective. The recent mapping of the expanding nebula’s 3-D structure, based in part on this clear Hubble image,indicates that the nebula is a relatively dense, donut-like ring wrapped around the middle of an (American) football-shaped cloud of glowing gas. Our view from planet Earth looks down the long axis of…

蛇妖星云

蛇妖星云

ByNASA中文

2023年3月17日 The Medusa Nebula Image Credit & Copyright: Martin Bradley Chesterfield Astronomical Society Explanation: Braided and serpentine filaments of glowing gas suggest this nebula’s popular name, The Medusa Nebula. Also known as Abell 21, this Medusa is an old planetary nebula some 1,500 light-years away in the constellation Gemini. Like its mythological namesake, the nebula is associated with a dramatic transformation. The planetary nebula phase represents a final stage in the evolution of low mass stars like the sun as they transform themselves from red giants to hot white dwarf stars and in the process shrug off their outer layers. Ultraviolet radiation from the hot star powers the nebular glow. The Medusa’s transforming star is the faint one near the center of the overall bright…