The light that the NASA/ESA Hubble Space Telescope collected to create this image reached the telescope after a journey of 250 million years. Its source was the spiral galaxy UGC 11397, which resides in the constellation Lyra (The Lyre). At first glance, UGC 11397 appears to be an average spiral galaxy: it sports two graceful spiral arms that are illuminated by stars and defined by dark, clumpy clouds of dust.
What sets UGC 11397 apart from a typical spiral lies at its center, where a supermassive black hole containing 174 million times the mass of our Sun grows. As a black hole ensnares gas, dust, and even entire stars from its vicinity, this doomed matter heats up and puts on a fantastic cosmic light show.
Material trapped by the black hole emits light from gamma rays to radio waves, and can brighten and fade without warning. But in some galaxies, including UGC 11397, thick clouds of dust hide much of this energetic activity from view in optical light. Despite this, UGC 11397’s actively growing black hole was revealed through its bright X-ray emission — high-energy light that can pierce the surrounding dust. This led astronomers to classify it as a Type 2 Seyfert galaxy, a category used for active galaxies whose central regions are hidden from view in visible light by a donut-shaped cloud of dust and gas.
Using Hubble, researchers will study hundreds of galaxies that, like UGC 11397, harbor a supermassive black hole that is gaining mass. The Hubble observations will help researchers weigh nearby supermassive black holes, understand how black holes grew early in the universe’s history, and even study how stars form in the extreme environment found at the very center of a galaxy.
Text credit: ESA
Image credit: ESA/Hubble & NASA, M. J. Koss, A. J. Barth
为了拍摄这张图像，NASA/ESA哈勃太空望远镜所收集的光经历了长达2.5亿年的旅程才到达望远镜。这束光的源头是螺旋星系UGC 11397，它位于天琴座内。乍一看，UGC 11397似乎是一颗普通的螺旋星系：它拥有两条优雅的旋臂，由恒星照亮，并被暗淡、簇状的尘埃云勾勒出形状。
然而，UGC 11397与典型螺旋星系不同之处在于它的中心，那里存在着一个质量相当于1.74亿个太阳的超大质量黑洞。随着黑洞捕获周围的气体、尘埃，甚至整颗恒星，这些注定被吞噬的物质会被加热，随之上演一场壮观的宇宙光影秀。
被黑洞俘获的物质会发出从伽玛射线到无线电波的各种光，并可能毫无预兆地变亮或变暗。但在包括UGC 11397在内的一些星系中，厚厚的尘埃云在可见光波段隐藏了大部分能量活动。尽管如此，UGC 11397中心活跃增长的黑洞通过明亮的X射线辐射显露了踪迹——这种高能光能够穿透周围的尘埃。这使天文学家将其归类为2型西佛星系，这是一种中心区域在可见光下被甜甜圈状尘气环遮挡的活跃星系。
研究人员将利用哈勃望远镜研究数百个像UGC 11397这样拥有超大质量黑洞并正在增重的星系。哈勃的观测将帮助科学家测定近邻星系中超大质量黑洞的质量，理解早期宇宙中黑洞是如何增长的，甚至研究恒星如何在星系最中心这样极端的环境中形成。
文字来源: ESA
图片来源: ESA/Hubble & NASA, M. J. Koss, A. J. Barth
