2025年7月5日
Ou4: The Giant Squid Nebula
Image Credit & Copyright: Massimo Di Fusco
Explanation: Difficult to capture, this mysterious, squid-shaped interstellar cloud spans nearly three full moons in planet Earth’s sky. Discovered in 2011 by French astro-imager Nicolas Outters, the Squid Nebula’s bipolar shape is distinguished here by the telltale blue emission from doubly ionized oxygen atoms. Though apparently surrounded by the reddish hydrogen emission region Sh2-129, the true distance and nature of the Squid Nebula have been difficult to determine. Still, one investigation suggests Ou4 really does lie within Sh2-129 some 2,300 light-years away. Consistent with that scenario, the cosmic squid would represent a spectacular outflow of material driven by a triple system of hot, massive stars, cataloged as HR8119, seen near the center of the nebula. If so, this truly giant squid nebula would physically be over 50 light-years across.
Tomorrow’s picture: north pole of Mars
Ou4: 巨乌贼星云
影像提供与版权: Massimo Di Fusco
说明: 在地球的天空中，这团绵延将近3个满月宽度的神秘乌贼状星际云气，相当难以捕捉拍摄。由法国天文摄影者奥特斯（Nicolas Outters）发现于2011年的乌贼星云（Ou4），其双极瓣的结构，因这幅影像所记录的特征性双电离氧原子之蓝绿辐射而变得清晰可辨。虽然乌贼星云看似外头包覆着泛红的氢辐射区Sh2-129，然而，其真实的距离及本质至今仍难以确认。不过，不久前的一项研究指出，Ou4的确是在距离约2,300光年远的发射星云SH2-129之内。在此情境下，这尾宇宙级的乌贼，可能是从炽热大质量的三合星系统（编录号为HR8119）外泛的物质。如此为真，这团庞大的乌贼星云之身宽会超过50光年。（Giant Squid Nebula 巨乌贼星云）
明日的图片: north pole of Mars
