Ring Nebula

"The NASA Hubble Space Telescope has captured the sharpest view yet of the most famous of all planetary nebulae, the Ring Nebula (M57). In this October 1998 image, the telescope has looked down a barrel of gas cast off by a dying star thousands of years ago. This photo reveals elongated dark clumps of material embedded in the gas at the edge of the nebula; the dying central star floating in a blue haze of hot gas. The nebula is about a light-year in diameter and is located some 2,000 light-years from Earth in the direction of the constellation Lyra. The colors are approximately true colors. The color image was assembled from three black-and-white photos taken through different color filters with the Hubble telescope's Wide Field and Planetary Camera 2. Blue isolates emission from very hot helium, which is located primarily close to the hot central star. Green represents ionized oxygen, which is located farther from the star. Red shows ionized nitrogen, which is radiated from the coolest gas, located farthest from the star. The gradations of color illustrate how the gas glows because it is bathed in ultraviolet radiation from the remnant central star, whose surface temperature is a white-hot 216,000 degrees Fahrenheit (120,000 degrees Celsius). " (NASA description).

NASA哈勃太空望远镜捕捉到了迄今为止最清晰的图像，展示了所有行星状星云中最著名的那个，即环状星云（M57）。在这张1998年10月的图像中，望远镜望向了数千年前一颗垂死恒星抛出的气体柱。这张照片揭示了嵌入星云边缘的延伸暗团块，其中一颗垂死的中心恒星漂浮在蓝色的热气体中。星云直径约为一个光年，位于天琴座方向约2000光年之外。颜色大致是真实颜色。这张彩色图像是由使用哈勃空间望远镜的广域和行星相机2拍摄的三张黑白照片通过不同颜色滤光片组合而成。蓝色代表非常热的氦的发射，主要位于靠近热中心恒星的区域。绿色代表电离的氧，位于更远的区域。红色显示电离的氮，来自最冷的气体，位于最远的区域。颜色的渐变说明了气体因受到中心恒星残留部分的紫外辐射而发光，该恒星的表面温度高达216,000华氏度（120,000摄氏度）。