科学家发现了没有任何暗物质的神秘星系

True to its name, dark matter has long been one of the universe's biggest mysteries. It is, after all, invisible, emitting no light whatsoever. And yet, we know it exists by the gravitational strings it pulls. Stars, literally, dance to the beat of dark matter.

正如其名，暗物质一直是宇宙中最大的谜团之一。毕竟，它是看不见的，不发出任何光。然而，我们知道它是通过它所拉动的引力弦而存在的。毫不夸张地说，恒星会随着暗物质的节奏起舞。

We have never seen a speck of it, but scientists say the universe is oozing with dark matter. (Photo: pixelparticle/Shutterstock)

"Motions of the stars tell you how much matter there is," Yale University researcher Pieter van Dokkum noted in 2016. "They don't care what form the matter is, they just tell you that it's there."

2016年，耶鲁大学研究员Pieter van Dokkum指出:“恒星的运动告诉你有多少物质。”“他们不关心物质的形式，他们只告诉你物质就在那里。”

At the time, van Dokkum was hailing the discovery of a galaxy with unusually high levels of dark matter — a place that boasts 99.99 percent of the stuff. On average, dark matter is estimated to make up around 27 percent of the universe.

当时，范多克姆正在为发现一个暗物质含量异常高的星系而欢呼——这个星系拥有99.99%的暗物质。据估计，暗物质平均占宇宙的27%左右。

But now researchers have made a discovery that could shatter our existing theory about how the universe is formed: No less than 19 galaxies seem to be missing dark matter altogether. Instead, dark matter's nemeses, called baryons, seem to dominate these dwarf galaxies.

但现在研究人员有了一项发现，可能会颠覆我们现有的关于宇宙形成的理论:至少有19个星系似乎完全没有暗物质。相反，暗物质的对手——重子——似乎主宰着这些矮星系。

Baryonic matter, comprising protons and neutrons, is the stuff we're more accustomed to — the matter scientists can relatively easily detect and measure. These newly discovered galaxies may be entirely composed of ordinary, run-of-the-mill baryonic matter.

重子物质，包括质子和中子，是我们更熟悉的物质——科学家可以相对容易地探测和测量这些物质。这些新发现的星系可能完全由普通的，运行的重子物质组成。

Dark matter is typically detected by the influence of its gravity on stars. (Photo: Vladimir Arndt/Shutterstock)

In the research paper, published in the journal Nature Astronomy, measured the swirl of 19 galaxies. That swirl factor tells scientists how much dark matter a galaxy contains. More specifically, they looked at the H1 rotation factor in these galaxies. That's the motion of hydrogen atoms as they're being swished around under dark matter's inexorable influence.

发表在《自然天文学》杂志上的研究论文测量了19个星系的旋涡。旋流因子告诉科学家星系中有多少暗物质。更具体地说，他们研究了这些星系中H1旋转因子。这是氢原子在暗物质不可阻挡的影响下被甩来甩去的运动。

And to their surprise, they found those hydrogen atoms were completely free from dark matter's sway. How is it possible that an ingredient so essential in the formation of galaxies could be missing? (Dark matter pulls atoms of gas together to form stars.)

令他们惊讶的是，他们发现这些氢原子完全不受暗物质的影响。星系形成中如此重要的成分怎么可能消失呢?(暗物质将气体原子聚集在一起形成恒星。)

Well, if their findings prove accurate, prevailing theories on how galaxies are formed from the interplay of dark and baryonic matter would need a complete reset.

好吧，如果他们的发现被证明是正确的，那么关于星系是如何由暗物质和重子物质相互作用而形成的流行理论将需要一个彻底的重置。

And it wouldn't be the first time scientists noted a galaxy seemingly bereft of dark matter. Last year, Yale researchers detected a similar phenomenon in a faraway galaxy known as NGC 1052–DF2.

这也不是科学家们第一次发现一个星系似乎没有暗物质。去年，耶鲁大学的研究人员在一个名为NGC 1052-DF2的遥远星系中发现了类似的现象。

What does it all mean for astrophysicists? There are still plenty of variables that may have thrown off their findings. For one thing, measuring the H1 rotation of a distant galaxy is easily skewed if its angle from Earth isn't calculated just right.

这对天体物理学家来说意味着什么?他们的研究结果仍然有很多变数。首先，测量一个遥远星系的H1旋转很容易发生偏斜，如果它与地球的角度计算不正确的话。

Another wildcard could be the presence of a supernova, which can have a profound effect on a galaxy's rotation. But if their findings are confirmed, then that ever-elusive material known as dark matter may have once again thrown science for a loop — and forced us to rethink how the universe came to be in the first place.

另一个未知因素可能是超新星的存在，它会对星系的旋转产生深远的影响。但如果他们的发现得到证实，那么被称为暗物质的难以捉摸的物质可能会再次把科学抛入一个循环——并迫使我们重新思考宇宙最初是如何形成的。