Ou4: A Giant Squid in a Flying Bat
Image Credit & Copyright: Yannick Akar
Explanation: A very faint but very large squid-like nebula is visible in planet Earth’s sky — but inside a still larger bat. The Giant Squid Nebula cataloged as Ou4, and Sh2-129 also known as the Flying Bat Nebula, are both caught in this cosmic scene toward the royal royal constellation Cepheus. Composed with 55 hours of narrowband image data, the telescopic field of view is 3 degrees or 6 Full Moons across. Discovered in 2011 by French astro-imager Nicolas Outters, the Squid Nebula’s alluring bipolar shape is distinguished here by the telltale blue-green emission from doubly ionized oxygen atoms. Though apparently completely surrounded by the reddish hydrogen emission region Sh2-129, the true distance and nature of the Squid Nebula have been difficult to determine. Still, a more recent investigation suggests Ou4 really does lie within Sh2-129 some 2,300 light-years away. Consistent with that scenario, Ou4 would represent a spectacular outflow driven by HR8119, a triple system of hot, massive stars seen near the center of the nebula. The truly giant Squid Nebula would physically be nearly 50 light-years across.
Tomorrow’s picture: pixels in space
影像提供与版权: Yannick Akar
说明: 在地球的天空中，极为昏暗、巨大、编录号为Ou4的乌贼星云和编录号为Sh2-129的飞蝠星云，同时出现在这幅远眺仙王座天区的影像里。这幅使用总曝光时数55小时的窄波段数据，所组合成的望远镜影像，其跨幅约为3度，相当为6个满月的宽度。在此图中，2011年由法国天文摄影者Nicolas Outters所发现的乌贼星云，为其赢得令名的双瓣结构，因双电离氧原子的特征蓝绿辐射而变得明显易辨。虽然乌贼星云看似完全包覆在Sh2-129的氢泛红发射区之内，但是它真实的距离和本质却一直难以测定。不论如何，一项最近的研究指出，Ou4的确位在距离约2,300光年远的发射星云Sh2-129之内。如此为真，那Ou4应是位在星云中心、编录号为HR8119的炽热大质量三合星系统外泛的大片物质。因此，乌贼星云庞大的身躯绵延了将近50光年。 （Squid Nebula 乌贼星云; Flying Bat Nebula 飞蝠星云）
明日的图片: pixels in space