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Searching the Heavens for Mountains

In the last few decades, astronomers¹ have discovered thousands of exoplanets orbiting other stars. Now, scientists want to know what they look like. Do they have oceans? Atmospheres? Researchers have even searched for signs of plant life and the glow of alien city lights—although they haven’t found any yet.

在过去的几十年里，天文学家发现了数千颗围绕其他恒星运行的系外行星。现在，科学家们想知道它们长什么样。那里有海洋吗?有大气?研究人员甚至还寻找植物生命的迹象和外星城市的光芒——尽管他们还没有找到。

“We’ve moved on from being excited about finding exoplanets to now having to get our kicks out of characterizing them.”

“我们已经从寻找系外行星的兴奋转向我们要去描述这些星球上。”

Moiya McTier, a graduate student at Columbia University and the host of the podcast So You Think You Can Science.

麦蒂尔是哥伦比亚大学的研究生，也是《你眼中的科学》(So You Think You Can Science)播客主持人。

Last year, McTier’s advisor² challenged her to find something else on exoplanets: evidence of extraterrestrial mountains. Because mountains could offer clues about what’s going on inside these planets.

去年，麦蒂尔的顾问向她提出挑战，要求她在太阳系外行星上找到其他的东西。因为山脉可以提供关于这些行星内部情况的线索。

“The way that those form is through the collision of tectonic plates or through lava³ building up in the same place over millions of years. And so that’s one of the most exciting things, in my opinion, that can come out of this project, is actually being able to figure out what’s underneath⁴ the surface of an exoplanet.”

“这些形态是通过构造板块的碰撞，或在数百万年的同一地点通过熔岩形成的。”所以这是最令人兴奋的事情之一，在我看来，可以从这个角度出发，就能够找出一颗系外行星表面之下的东西。

The trick was how to do it. Modern telescopes are powerful, but they can’t capture pictures of exoplanets. Instead, a common way astronomers detect them is by watching as they pass in front of their star, blotting⁵ out some of the light. McTier riffed on this idea to find a way to look for mountains.

方法在于如何去做。现代的望远镜是强大的，但它们不能捕捉系外行星的照片。取而代之的是，天文学家通过观察行星在恒星前经过时，遮挡光的情况。麦蒂尔在这个想法中，找到了寻找山脉的方法。

“And so, what we are doing with this mountains project is saying, okay, if a planet has a mountain on it and if that planet is rotating, then the mountain will show up in silhouette⁶. And the silhouette will change, because the planet’s rotating. So, we can study that changing silhouette—that changing shadow—to get an idea of what the surface of the planet looks like.”

“所以，我们在这个山脉项目中所做的就是说，好的，如果一个行星上有一座山，如果这个行星正在旋转，那么这座山就会出现轮廓。而轮廓出现改变，是因为这个星球正在旋转。因此，我们可以研究这种不断变化的轮廓即阴影的改变，来了解这个星球表面的样子。”

McTier tested the technique by modeling how the rocky planets of our solar system would look through modern telescopes like the James Webb if they were far away.

麦蒂尔通过建模太阳系的岩石行星，是如何通过詹姆斯韦伯等现代望远镜来观察这些技术，如果他们很远的话，我们会对这种技术进行测试。

“And we were pretty heartbroken when found out that it wouldn’t be possible.”

But McTier calculated that it might be doable with something like the Extremely Large Telescope, which is currently under construction in Chile. Even this telescope probably wouldn’t be able to measure the topography of a Mars-like body if it orbited a large star like our Sun. But if that planet circled a smaller star, like a white dwarf⁷, it would block out enough light to be detectible. The research is in the Monthly Notices of the Royal Astronomical⁸ Society.

“当发现这是不可能的时候，我们非常伤心。”但是麦蒂尔计算出，它可能适用于智利目前正在建设的极大望远镜。即使这个望远镜可能无法测量火星般的地形，如果它绕着像我们的太阳这样的大型恒星旋转。但是如果这颗行星围绕着一颗小矮星，就像一颗白矮星一样，它会挡住足够的光线以被探测到。这项研究结果发表在《皇家天文学会月刊》中。

So, one day soon we may be able to confirm the existence of exoplanetary mountains. And with even better telescopes, maybe molehills. Or even moles⁹.

所以，很快有一天，我们可以确认外行星山脉的存在。可能是用更先进的望远镜，也许是摩尔望远镜。