Black holes are common. But actually counting them is no easy task. Even the brightest can be hard to see. Of course, “bright black holes” is a bit of an oxymoron. But when supermassive black holes at the center of a galaxy feed, the material falling into them heats up, giving off a bright glow across the electromagnetic spectrum.
黑洞是普遍存在的现象。但实际上要统计黑洞的数量并非易事。即使最耀眼的地方也很难看见。当然,用明亮来修饰黑洞有点矛盾。然而,当星系中心质量超级大的黑洞“吞食”时,落入其中的物质便会升温,发出一道明亮的光,通过电磁波频谱可以显示出来。
Infrared light in particular is good to look for when black-hole hunting. Some feasting black holes are obscured by gas and dust, which absorbs much of their glow—but they still shine in the infrared.
在黑洞“捕捉”物质时,红外线尤其容易被找到。一些正在“享受盛宴”的黑洞被气体和灰尘所遮蔽,它们吸收掉大多数光线——但仍会发出红外光线。
It's no surprise, then, that NASA's infrared WISE spacecraft found a bunch. WISE launched in 2009 to survey the entire sky in the infrared. Now researchers have used WISE data to count the luminous black holes in a well-known corner of the sky called the COSMOS field. In just that tiny region, WISE found about 130 glowing black holes, or active galactic nuclei. The study will appear in the Astrophysical Journal.
美国宇航局的“智慧号”红外探测器发现了许多这类光线,这并不足以为奇。“智慧号”发射于2009年,用以探测整个天空的红外线。现在研究人员已经使用“智慧号”发送的数据计算著名的天空一角——被叫做COSMOS领域里的黑洞数量。在这块微小的区域,智慧号发现了130个发光的黑洞或活动星系核。这项研究将出现在天文物理期刊上。
Extrapolating from this small area, at least two million active black holes dot the sky, confirming that these extreme astrophysical objects are common indeed.
根据这块小区域可以推断,天空中至少散步着200万个活跃的黑洞,这也证实了这些极端天体的存在确实很普遍。
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