'Galaxy-sized' observatory sees potential hints of gravitational waves

“银河大小”的天文台看到了引力波的潜在提示

by University of Colorado at Boulder

科罗拉多大学博尔德分校

This illustration shows the NANOGrav project observing cosmic objects called pulsars in an effort detect gravitational waves - ripples in the fabric of space. The project is seeking a low-level gravitational wave background signal that is thought to be present throughout the universe.Credit: NANOGrav/T. Klein

此图显示了NANOGrav项目，该项目观察被称为脉冲星的宇宙物体，以力图检测引力波-空间结构中的波纹。该项目正在寻找被认为存在于整个宇宙中的低水平引力波背景信号。图片来源：NANOGrav / T。克莱因

Scientists have used a "galaxy-sized" space observatory to find possible hints of a unique signal from gravitational waves, or the powerful ripples that course through the universe and warp the fabric of space and time itself.

科学家们使用了一个“银河大小”的太空天文台，来寻找引力波中独特信号的可能提示，或者是贯穿宇宙的强大涟漪，扭曲了时空结构。

The new findings, which appeared recently in The Astrophysical Journal Letters, hail from a U.S. and Canadian project called the North American Nanohertz Observatory for Gravitational Waves (NANOGrav).

这一新发现最近发表在《天体物理学杂志快报》上，该发现来自美国和加拿大一个名为“北美纳赫兹引力波纳米天文台”（NANOGrav）的项目。

For over 13 years, NANOGrav researchers have pored over the light streaming from dozens of pulsars spread throughout the Milky Way Galaxy to try to detect a "gravitational wave background." That's what scientists call the steady flux of gravitational radiation that, according to theory, washes over Earth on a constant basis. The team hasn't yet pinpointed that target, but it's getting closer than ever before, said Joseph Simon, an astrophysicist at the University of Colorado Boulder and lead author of the new paper.

十三年来，NANOGrav研究人员仔细研究了遍布整个银河系的数十个脉冲星发出的光，以试图检测“引力波背景”。这就是科学家所说的稳定的重力辐射通量，根据理论，它不断地在地球上冲洗。科罗拉多大学博尔德分校的天体物理学家，新论文的主要作者约瑟夫·西蒙说，研究小组尚未确定这个目标，但是比以往任何时候都更加紧密。

"We've found a strong signal in our dataset," said Simon, a postdoctoral researcher in the Department of Astrophysical and Planetary Sciences. "But we can't say yet that this is the gravitational wave background."

天体物理与行星科学系的博士后研究员西蒙说：“我们在数据集中发现了一个强烈的信号。” “但是我们还不能说这就是引力波的背景。”

In 2017, scientists on an experiment called the Laser Interferometer Gravitational-Wave Observatory (LIGO) won the Nobel Prize in Physics for the first-ever direct detection

2017年，科学家在一项名为``激光干涉仪引力波天文台（LIGO）''的实验中首次获得了诺贝尔物理学奖

of gravitational waves. Those waves were created when two black holes slammed into each other roughly 130 million lightyears from Earth, generating a cosmic shock that spread to our own solar system.

引力波。这些波是在两个黑洞从地球大约1.3亿光年相互撞击时产生的，并产生了宇宙冲击，并传播到了我们自己的太阳系。

That event was the equivalent of a cymbal crash—a violent and short-lived blast. The gravitational waves that Simon and his colleagues are looking for, in contrast, are more like the steady hum of conversation at a crowded cocktail party.

那件事相当于a坠毁-剧烈而短暂的爆炸。相比之下，西蒙和他的同事正在寻找的引力波更像是在一个拥挤的鸡尾酒会上持续的嗡嗡声。

Detecting that background noise would be a major scientific achievement, opening a new window to the workings of the universe, he added. These waves, for example, could give scientists new tools for studying how the supermassive black holes at the centers of many galaxies merge over time.

他补充说，检测到背景噪声将是一项重大的科学成就，从而为宇宙的运转打开了一个新窗口。例如，这些波可以为科学家提供新的工具，以研究许多星系中心的超大质量黑洞如何随时间融合。

"These enticing first hints of a gravitational wave background suggest that supermassive black holes likely do merge and that we are bobbing in a sea of gravitational waves rippling from supermassive black hole mergers in galaxies across the universe," said Julie Comerford, an associate professor of astrophysical and planetary science at CU Boulder and NANOGrav team member.

“引力波背景的这些诱人的第一暗示表明，超大质量黑洞可能会合并，并且我们正处于由整个银河系中的超大质量黑洞合并引起的引力波海中摇曳，”朱莉·科默福德说， CU Boulder和NANOGrav团队成员的天体物理学和行星科学。

Simon will present his team's results at a virtual press conference on Monday at the 237th meeting of the American Astronomical Society.

西蒙（Simon）将于周一在美国天文学会（American Astronomicalnomic Society）的第237次会议上举行的虚拟新闻发布会上介绍其团队的研究结果。

Galactic lighthouses

银河灯塔

Through their work on NANOGrav, Simon and Comerford are part of a high stakes, albeit collaborative, international race to find the gravitational wave background. Their project joins two others out of Europe and Australia to make up a network called the International Pulsar Timing Array.

通过他们在NANOGrav上的工作，Simon和Comerford成为了一场颇有争议的赛事，尽管这是一场国际合作，旨在寻找引力波背景。他们的项目与来自欧洲和澳大利亚的其他两个国家一起组成了一个名为“国际脉冲星计时阵列”的网络。

Simon said that, at least according to theory, merging galaxies and other cosmological events produce a steady churn of gravitational waves. They're humungous—a single wave, Simon said, can take years or even longer to pass Earth by. For that reason, no other existing experiments can detect them directly.

西蒙说，至少根据理论，合并的星系和其他宇宙事件会产生稳定的引力波。它们实在太小了，西蒙说，单浪过地球可能需要几年甚至更长的时间。因此，其他现有实验无法直接检测到它们。

"Other observatories search for gravitational waves that are on the order of seconds," Simon said. "We're looking for waves that are on the order of years or decades."

西蒙说：“其他天文台都在搜索几秒钟的引力波。” “我们正在寻找数年或数十年量级的波浪。”

He and his colleagues had to get creative. The NANOGrav team uses telescopes on the ground not to look for gravitational waves but to observe pulsars. These collapsed stars are the

他和他的同事们必须有创造力。 NANOGrav小组在地面上使用望远镜不是寻找引力波而是观察脉冲星。这些坍塌的恒星是

lighthouses of the galaxy. They spin at incredibly fast speeds, sending streams of radiation hurtling toward Earth in a blinking pattern that remains mostly unchanged over the eons.

银河的灯塔。它们以令人难以置信的快速旋转，以闪烁的模式向地球发送辐射流，这些辐射流在整个世代几乎保持不变。

Simon explained that gravitational waves alter the steady pattern of light coming from pulsars, tugging or squeezing the relative distances that these rays travel through space. Scientists, in other words, might be able to spot the gravitational wave background simply by monitoring pulsars for correlated changes in the timing of when they arrive at Earth.

西蒙解释说，引力波改变了来自脉冲星的光的稳定模式，拉扯或挤压了这些射线在太空中传播的相对距离。换句话说，科学家可能仅通过监视脉冲星到达地球时机的相关变化，就能发现引力波背景。

"These pulsars are spinning about as fast as your kitchen blender," he said. "And we're looking at deviations in their timing of just a few hundred nanoseconds."

他说：“这些脉冲星的旋转速度与厨房搅拌机一样快。” “而且我们正在研究它们的时间偏差只有几百纳秒。”

Something there

那里的东西

To find that subtle signal, the NANOGrav team strives to observe as many pulsars as possible for as long as possible. To date, the group has observed 45 pulsars for at least three years and, in some cases, for well over a decade.

为了发现这种微妙的信号，NANOGrav小组努力在尽可能长的时间内观察尽可能多的脉冲星。迄今为止，该小组至少在三年中观测到了45个脉冲星，在某些情况下，已经观测了十多年。

The hard work seems to be paying off. In their latest study, Simon and his colleagues report that they've detected a distinct signal in their data: Some common process seems to be affecting the light coming from many of the pulsars.

艰苦的工作似乎正在得到回报。西蒙和他的同事们在最新研究中报告说，他们在数据中检测到了一个明显的信号：一些共同的过程似乎正在影响许多脉冲星发出的光。

"We walked through each of the pulsars one by one. I think we were all expecting to find a few that were the screwy ones throwing off our data," Simon said. "But then we got through them all, and we said, 'Oh my God, there's actually something here.'"

西蒙说：“我们逐一遍历了每个脉冲星。我认为我们都希望找到一些不可靠的脉冲星。” “但是后来我们经历了所有的一切，我们说，'哦，我的上帝，这里确实有东西。'”

The researchers still can't say for sure what's causing that signal. They'll need to add more pulsars to their dataset and observe them for longer periods to determine if it's actually the gravitational wave background at work.

研究人员仍然不能确定是什么引起了该信号。他们将需要向其数据集中添加更多的脉冲星，并对其进行更长时间的观察，以确定其是否实际上是引力波背景。

"Being able to detect the gravitational wave background will be a huge step but that's really only step one," he said. "Step two is pinpointing what causes those waves and discovering what they can tell us about the universe."

他说：“能够检测到引力波背景将是巨大的一步，但这实际上只是第一步。” “第二步是找出导致这些波动的原因，并发现它们可以告诉我们有关宇宙的信息。”

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