2026年1月23日
Planetary Nebula Abell 7
Image Credit & Copyright: Martin Pugh
Explanation: Very faint planetary nebula Abell 7 is about 1,800 light-years distant. It lies just south of Orion in planet Earth’s skies toward the constellation Lepus, The Hare. Posing with scattered Milky Way stars, its generally simple spherical shape about 8 light-years in diameter is revealed in this deep telescopic image. The beautiful and complex shapes seen within the cosmic cloud are visually enhanced by the use of long exposures and narrowband filters that capture emission from hydrogen and oxygen atoms. Otherwise Abell 7 would 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. But its central star, seen here as a fading white dwarf, is some 10 billion years old.
Tomorrow’s picture: Earthset
行星状星云Abell 7
影像提供与版权: Martin Pugh
说明: 极为黯淡的行星状星云Abell 7距离我们约1,800光年。在天球中，它位于猎户座以南、朝向天兔座的方向。这张深空望远镜影像中包含了Abell 7与零散分布的银河系恒星，其整体轮廓呈现出简单的球状结构，直径约8光年。利用长时间曝光与窄频滤镜，有效捕捉到氢与氧原子的发射光谱，使得这团宇宙云气内部美丽而复杂的细节更加鲜明可见，否则Abell 7的亮度过于微弱，几乎无法以肉眼欣赏。行星状星云代表恒星演化中非常短暂的最后阶段，约50亿年后，我们的太阳也将经历这样的过程，位于星云中心那颗类似太阳的恒星会抛散其外层物质，形成发光的星云壳层。Abell 7的年龄估计为2万年；然而，其中心已演化为逐渐黯淡的白矮星的恒星，已经有大约100亿年的历史了。
明日的图片: Earthset
