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Building a Better Mirror for Telescopes

为望远镜打造更优质镜面

To study the heavens, it's all about the photons. "We in astronomy are always greedy. We want every photon we can collect." Drew Phillips, astronomer¹ at University of California Observatories². More photons, he says, basically means more science about incredibly faint, distant objects.

研究天空，就是研究光子。“研究天文学的人都很贪婪，因为我们总是奢望能收集到每一个光子。”加州大学天文台的天文学家德鲁·菲利普斯如是说。他所说的想要收集更多光子，基本上意味着收集关于那些极其微弱且遥远的物体更多科学信息。

And that's where the optics problem comes in. Because incoming light reflects off several mirrors before it comes out the business end of a telescope. And mirrors aren't perfectly³ reflective. The traditional mirror coating, aluminum⁴, reflects only about 90 percent of light. Bounce that light around a few times in a telescope, and you lose valuable photons.

就是这样才引发了光学问题的出现。因为入射光在射出望远镜的尖端之前，会反射出好几个镜面。而镜面却无法完全反射。传统镜面镀膜的材质是铝，它只能反射90%的光。光线在望远镜里来回反射几次，就会失去有价值的光子。

"The throughput, the actual number of photons that are detected in the end in a modern spectrograph, you're doing good if you get thirty percent."

“在现代光谱仪中最终能检测到的光子数量能达到30%就已经很不错了。”

So you want the most reflective material for your mirrors. Like silver, which reflects 97 to 99 percent of visible and infrared⁵ light, respectively. Big improvement over aluminum. But silver's got problems too. "It is finicky. It's subject to tarnish⁶, and oxidation, and corrosion⁷."

因此我们需要反射能力最好的材质来做镜面。比如银，它能分别反射97%的可见光和99%的红外光。比铝的反射率要高出许多。但银也有它的问题。“它很难掌控，易于失去光泽、被氧化和腐蚀。”

So Phillips and his team have borrowed a trick from the computer industry, called atomic layer deposition⁸. The technique allows them to take a silver-coated mirror—and coat it with extremely uniform layers of transparent⁹ aluminum oxide¹⁰, to protect against corrosion.

因此，菲利普斯和他的团队借用了计算机行业中的一个技巧，即“原子层沉积”技术。这种技术可以让他们采用镀银镜，并为其涂上极其均匀的透明氧化铝层，以防止其被腐蚀。

And unlike the small-scale atomic deposition used in the electronics industry, this new machine--recently installed in a lab at U.C. Santa Cruz—is scaled up to coat mirror segments up to a meter in diameter. Meaning you could coat all 500 mirrors of a state-of-the-art telescope—like the planned Thirty Meter Telescope—in a matter of months.

与电子工业中使用的小规模原子沉积不同，最近安装在加州大学圣克鲁兹分校的实验室里的这台新机器，镜面被放大到直径为一米。也就是说，你可以在短短几个月内，将一台最先进的望远镜——比如那台30米长的望远镜中的500个镜面全部涂上一层透明氧化铝层。

When put to use, these better mirrors might allow astronomers¹¹ to capture more photons… and shed more light—literally—on faraway galaxies¹² and stars.

如果它被投入使用，天文学家将能够利用这些更优质的镜面采集到遥远的星系和恒星上的更多光子，并分出更多光线发现更多奥秘。