NASA·APOD每日天文一图2022.5.21 [超高清]

Very faint planetary nebula Abell 7 is some 1,800 light-years distant, just south of Orion in planet Earth's skies in the constellation Lepus, The Hare. Surrounded by Milky Way stars and near the line-of-sight to distant background galaxies, its generally simple spherical shape, about 8 light-years in diameter, is outlined in this deep telescopic image. Within its confines are beautiful, more complex details enhanced by the use of narrowband filters. Emission from hydrogen is shown in reddish hues with oxygen emission mapped to green and blue colors, giving Abell 7 a natural appearance that would otherwise be much too faint to be appreciated by eye. A planetary nebula represents a very brief final phase in stellar evolution that our own Sun will experience 5 billion years hence, as the nebula's central, once sun-like star shrugs off its outer layers. Abell 7 itself is estimated to be 20,000 years old. Its central star is seen here as a fading white dwarf some 10 billion years old. 

非常暗淡的行星状星云Abell 7距离我们大约1800光年远，就在猎户座以南，猎户座位于兔子星座的地球天空中。在这张深度望远镜图像中，它被银河系恒星包围，靠近遥远背景星系的视线，通常是简单的球形，直径约8光年。在它的范围内是美丽的，更复杂的细节通过窄带滤波器的使用而增强。氢的发射以微红色显示，而氧的发射则映射为绿色和蓝色，这给了阿贝尔7一个自然的外观，否则它会太微弱而无法被眼睛欣赏。行星状星云代表了恒星演化的一个非常短暂的最后阶段，我们自己的太阳将在50亿年后经历这一阶段，因为该星云的中心，曾经类似太阳的恒星摆脱了外层。阿贝尔7号本身估计有20000年的历史。它的中心恒星在这里被视为一颗大约100亿年前正在衰退的白矮星。