科学美国人60秒 宇宙模拟显示了缺乏暗物质的星系如何对抗巨人并生存下来（在线收听）

Cosmic Simulation Shows How Dark-Matter-Deficient Galaxies Confront Goliath and Survive

宇宙模拟显示了缺乏暗物质的星系如何对抗巨人并生存下来

Joanna Thompson: This is Scientific American’s 60 second science. I’m Joanna Thompson.

In 2018, a group of astronomers from Yale discovered something odd: two galaxies that had almost no dark matter. The observation caused a commotion in scientific circles, because it seemed to fly in the face of everything that astrophysicists thought they knew about galaxy formation. But researchers may have just discovered the mechanism that makes these so-called “dark matter deficient galaxies” possible.

乔安娜·汤普森：这是《科学美国人》的60秒科学。我是乔安娜·汤普森。

2018年，耶鲁大学的一群天文学家发现了一些奇怪的东西：两个几乎没有暗物质的星系。这一观测结果在科学界引起了轩然大波，因为它似乎与天体物理学家认为他们知道的关于星系形成的一切都背道而驰。但研究人员可能刚刚发现了使这些所谓的“暗物质缺乏星系”成为可能的机制。

In astronomy, matter comes in two flavors: dark matter and baryons.

Adams: Baryons is a fancy way of saying regular matter.

Thompson: That’s Betsey Adams, an astronomer at Astron, the Netherlands’s Institute for Radio Astronomy who was not involved in the research. Unlike baryonic matter, dark matter is invisible.

在天文学中，物质有两种类型：暗物质和重子。

亚当斯：重子是一种表达常规物质的奇特方式。

汤普森：这是贝齐·亚当斯，荷兰射电天文学研究所天文学家，他没有参与这项研究。与重子物质不同，暗物质是看不见的。

Adams: The point of dark matter is that we can't see it, you know, there's no radiation from it, we don't observe it with our telescopes. What we observe is the baryons, the regular stuff. And so to infer the presence of Dark Matter, we look for its effects gravitationally.

亚当斯：暗物质的意义在于我们看不到它，你知道，它没有辐射，我们没有用望远镜观察它。我们观察到的是重子，普通物质。因此，为了推断暗物质的存在，我们寻找它的引力效应。

Thompson: Dark matter acts like the invisible glue that holds galaxies together. Around 85% of an average galaxy consists of dark matter, and without it, astronomers think that most galaxies wouldn’t have enough gravity to take shape.

汤普森：暗物质就像把星系粘在一起的无形胶水。平均约85%的星系由暗物质组成，没有暗物质，天文学家认为大多数星系都没有足够的引力来形成。

Stumbling across a galaxy without dark matter is a little like finding a hurricane with no wind. So, where the heck did the Yale astronomers’ dark matter-less galaxies come from? That question caught the attention of Jorge Moreno, an astronomer at Pomona College in Claremont, California.

在没有暗物质的星系中蹒跚前行，有点像在无风的飓风中发现自己。那么，耶鲁天文学家的无暗物质星系究竟从何而来？这个问题引起了加州克莱蒙特波莫纳学院天文学家豪尔赫·莫雷诺的注意。

Moreno: Many of us were freaking out. It was like a major challenge to our paradigm.

Thompson: Moreno is part of a team working on an expansive, highly detailed computer program designed to simulate merging galaxies. [Jorge Moreno et al., Galaxies lacking dark matter produced by close encounters in a cosmological simulation]

莫雷诺：我们很多人都吓坏了。这就像是对我们范式的重大挑战。

汤普森：莫雷诺是一个团队的成员，该团队正在开发一个扩展的、高度详细的计算机程序，用于模拟合并星系。

Moreno: This is what we call a cosmological simulation. You simulate a big chunk of the universe, you create a mini-universe in your computer.

Thompson: The simulation he works with follows the standard model of physics, which is rich in dark matter. But not every physicist is convinced that the standard model is correct.

莫雷诺：这就是我们所说的宇宙模拟。你模拟了宇宙的一大块，在你的电脑里创造了一个小宇宙。

汤普森：他所做的模拟工作遵循的是标准的物理模型，其中含有丰富的暗物质。但并不是每个物理学家都相信标准模型是正确的。

Moreno: There was another camp of people who said, you know what, it's time to just get rid of this model, this dark matter. It's a nice idea, but it's not really consistent with observations, that it's time to put it in the bin and think about something else. Maybe we need to modify the laws of physics or something like that.

莫雷诺：还有一个阵营的人说，你知道吗，是时候摆脱这个模型了，这个暗物质。这是一个好主意，但它与观察结果并不完全一致，是时候把它放进垃圾箱，考虑其他事情了。也许我们需要修改物理定律之类的东西。

Thompson: Hai-Bo Yu, a theoretical particle physicist at the University of California, Riverside, fell into that camp.

Yu: My group also got interested in this, so we wrote a paper saying that maybe the new physics, which is beyond the standard kind of dark matter theory, is needed. It's better to explain these two galaxies.

汤普森：加利福尼亚大学滨海分校的理论粒子物理学家海波郁落入了标准杆数。

余：我的团队也对这一点感兴趣，所以我们写了一篇论文说，也许需要新的物理学，它超越了暗物质理论的标准类型。最好解释一下这两个星系。

Thompson: But Moreno’s simulation offers a solution without throwing away conventional physics. Initially, his team was focused on massive galaxies. But when they looked more closely at the simulation’s tiny dwarf galaxies, a surprise popped out: seven of them lacked dark matter.

Each of these low-dark matter dwarves orbited a supermassive galaxy, the way a moon might orbit a planet. Moreno found that the seven galaxies hadn’t formed without dark matter; instead, their dark matter had been gradually stripped away as they crossed paths with their supermassive counterpart.

汤普森：但是莫雷诺的模拟提供了一个解决方案，而不抛弃传统物理。最初，他的团队专注于大质量星系。但当他们更仔细地观察模拟的微小矮星系时，一个惊喜突然出现：其中有七个缺乏暗物质。

每一个低暗物质矮星都围绕一个超大质量星系运行，就像月球绕行星运行一样。莫雷诺发现这七个星系的形成离不开暗物质；相反，当它们与超大质量的同类相遇时，它们的暗物质逐渐被剥离。

Moreno: We didn't design the simulation to find for these things. With it, they just appeared.

It preserves a paradigm. We, we basically say, you don't need to throw away the idea of dark matter, because we use a simulation with dark matter. And we were able to create galaxies without it.

莫雷诺：我们设计模拟不是为了找到这些东西。有了它，他们就出现了。

它保留了一种范式。我们，我们基本上说，你不需要抛弃暗物质的概念，因为我们使用暗物质的模拟。我们能够在没有它的情况下创造星系。

Thompson: For Yu, it was an exciting find.

Yu: I would say, congratulations, to the authors. It's a remarkable [piece of] work. And also, their results actually do not exclude the possibility to have new physics.

Thompson: The next step, according to Adams of Astron, is to verify Moreno’s results with observations.

对于Yu来说，汤普森的发现很令人兴奋。

余：我要向作者们表示祝贺。这是一件了不起的作品。而且，他们的结果实际上并不排除产生新物理的可能性。

汤普森：根据Astron的亚当斯的说法，下一步是通过观察来验证莫雷诺的结果。

Adams: The authors of the paper, that's something that I very much liked, which is they made a prediction, they said: we think that up to 30% of central galaxies in this mass range should have dark matter deficient satellite galaxies. So it would be a lot of work observationally, but you could then go test that.

亚当斯：这篇论文的作者，这是我非常喜欢的，他们做了一个预测，他们说：我们认为在这个质量范围内，多达30%的中心星系应该有缺乏暗物质的卫星星系。所以从观测角度来说，这将是一个很大的工作，但你可以去测试它。

Thompson: And for Moreno, the research takes on a personal dimension.

Moreno: I have indigenous roots, especially on the border of the U.S. and Mexico. And I have a friend, he's a professor of physics in Texas. And he's Cherokee. And he told me that the Cherokee tribe has seven clans. So I asked, Hey, can you ask the elders if they give me permission to use their names? And they said, Yes.

汤普森：对莫雷诺来说，这项研究涉及个人层面。

莫雷诺：我有自己的根，尤其是在美国和墨西哥边境。我有一个朋友，他是德克萨斯州的物理教授。他是切诺基人。他告诉我切罗基部落有七个部落。所以我问，嘿，你能问问长老们，他们是否允许我使用他们的名字吗？他们说，是的。

Thompson: He named the seven dark matter deficient galaxies after these clans: Bird, Deer, Long Hair, Paint, Wild Potato, Wolf, and Blue.

汤普森：他以鸟类、鹿、长发、颜料、野土豆、狼和蓝色等族命名了七个缺乏暗物质的星系。

Moreno: The reason this resonates with me and I think would resonate with any person of Indigenous ancestry is because that's basically what happened to us. Like, are we in the process of colonization, we lost our language, we lost our traditions/I don't know what my music is, I have a European name, I speak European languages. 

莫雷诺：这件事引起我的共鸣，我认为会引起任何有土著血统的人的共鸣，是因为这基本上就是发生在我们身上的事情。比如，我们是否在殖民地化的过程中，我们失去了我们的语言，我们失去了我们的传统/我不知道我的音乐是什么，我有一个欧洲名字，我说欧洲语言。

But I'm still here. And we're still here. These galaxies felt like that. They didn't assimilate. And they weren't destroyed, they confronted the Goliath, and they're surviving.

Thompson: For 60-second Science, I’m Joanna Thompson

但我还在这里。我们还在这里。这些星系就是这样的感觉。他们没有同化。他们没有被摧毁，他们对抗了歌利亚，他们活了下来。

汤普森：60秒科学，我是乔安娜·汤普森