Astronomers spot 1st coronal mass ejection from an alien star — and that's bad news in the search for life

天文学家们观察到恒星第一次日冕物质抛射——此乃寻找生命起源的噩耗

Thanks to the European Space Agency (ESA) spacecraft XMM-Newton, astronomers have seen a powerful explosion of plasma erupting from a distant star for the first time. We have seen (and felt) plenty of these coronal mass ejections (CMEs) from the sun, but even though we have long thought other stars expel such powerful outflows of superheated gas and magnetic field, astronomers had never before spotted them in any convincing way.

在欧洲航天局（ESA）航天器XMM-Newton帮助，天文学家首次发现了遥远恒星喷发的强大等离子体的爆炸现象。我们已观察（并感觉）了大量来自太阳的日冕物质抛射(CME)，但一直以来我们都认为其他恒星的确会排出如此强大的过热气体和磁场，但天文学家们以前从未以如此令人信服的方式发现它们。

This first extra-solar CME, which erupted from a red dwarf star, wasn't any run-of-the-mill stellar blast either. This CME was dense enough and carried enough energy to strip away the atmosphere of any closely orbiting planet, with the ejected material traveling at 5.4 million miles per hour (2,400 kilometers per second). That speed, around 3,500 times as fast as a Lockheed Martin F-16 jet fighter, is something that is only observed in around 1 in 2,000 CMEs from our sun.

这首次发现从红矮星爆发的太阳系外日冕物质抛射，它并非普通的恒星爆炸。这种高密度日冕物质抛射，携带的能量足以剥离任一近距离轨道行星的大气层，喷射的物质以高达每小时540万英里（每秒2400公里）的速度迅速扩散。这个速度有洛克希德·马丁公司F-16喷气式战斗机的3,500倍，只有在大约1/2000的日冕物质抛射中才能观察到。

The atmosphere-stripping potential of this outburst means the observation of this CME could help astronomers better refine which extrasolar planets, or exoplanets, orbiting distant stars are capable of supporting life.

这次爆发的巨大大气剥离潜力意味着对这次日冕物质抛射的观测可助天文学家们更好地确定哪些围绕遥远恒星运行的太阳系外行星或系外行星能够支持生命的存在。

"Astronomers have wanted to spot a CME on another star for decades," team member Joe Callingham of the Netherlands Institute for Radio Astronomy (ASTRON) said in a statement. "Previous findings have inferred that they exist, or hinted at their presence, but haven’t actually confirmed that material has definitively escaped out into space. We’ve now managed to do this for the first time."

荷兰射电天文学研究所(ASTRON)的团队成员乔·卡林厄姆(Joe Callingham)声明：“几十年来，天文学家们一直期望在另一颗恒星上发现日冕物质抛射," “之前的发现已推断出它们的确存在，或暗示了它们的存在，但实际上该证实物质已经明确逃逸到太空中。我们现在首次成功做到了。”

The team's research was published on Wednesday (Nov. 12) in the journal Nature.

该研究用于周三（11月12日）的《自然》杂志上。

The discovery of this extra-solar CME was aided by the Low-Frequency Array (LOFAR) radio telescope, which is capable of detecting radio signals that are created by CMEs when they ripple through the outer layers of stars and emerge into interplanetary space. This creates a shock wave and an associated telltale burst of light in the radio wave region of the electromagnetic spectrum.

这种太阳系外日冕物质抛射的研究在低频阵列（LOFAR）射电望远镜的帮助，能够探测日冕物质抛射穿过恒星外层并进入行星际空间时产生的射电信号。这在电磁波谱的无线电波区域冲击波和相关的指示性光线。

"This kind of radio signal just wouldn’t exist unless material had completely left the star’s bubble of powerful magnetism," Callingham said. "In other words, it's caused by a CME."

卡林厄姆说：“除非物质完全离开恒星的强大磁性气泡，否则这种无线电信号绝无存在的可能。”，“就是，它是由CME引起的。”

This extra-solar CME was first spotted in data from LOFAR thanks to a new data processing technique. XMM-Newton was then used to determine the temperature of the star that created it, its rotational speed, and its brightness in X-ray light. This revealed that this red dwarf, located around 130 light-years away, has around half the mass of the sun, but rotates around 20 times faster than our star and has a magnetic field around 300 times more powerful than the solar magnetic field.

由于一种新的数据处理技术，这种太阳外CME首次在LOFAR的数据中被发现。然后，XMM-Newton被用来确定产生它的恒星的温度、旋转速度和X射线亮度。这表明，这颗红矮星距离我们大约130光年，质量大约是太阳的一半，但自转速度比我们的恒星快20倍，磁场比太阳磁场强300倍。

"We needed the sensitivity and frequency of LOFAR to detect the radio waves," team member David Konijn, a PhD student at ASTRON, explained. "And without XMM-Newton, we wouldn’t have been able to determine the CME’s motion or put it in a solar context, both crucial for proving what we’d found. Neither telescope alone would have been enough – we needed both."

“我们利用LOFAR的灵敏度和频率的技术来检测无线电波，”团队成员ASTRON的博士生David Konijn解释说，“如果没有XMM-Newton这项技术，我们就无法确定CME的运动轨迹或将其置于太阳环境中进行研究，这两者都对于证明我们的发现是否正确都至关重要。仅靠两台望远镜都不够我们用——我们两台都需要。”

This research could also help us better understand the CMEs launched by the sun and how they drive space weather around Earth.

这项研究还能帮助我们深刻明白太阳发射的日冕物质抛射物和它们如何驱动地球周围的空间天气。

"XMM-Newton is now helping us discover how CMEs vary by star, something that’s not only interesting in our study of stars and our sun, but also our hunt for habitable worlds around other stars," said Erik Kuulkers, an ESA XMM-Newton Project Scientist. "It also demonstrates the immense power of collaboration, which underpins all successful science. The discovery was a true team effort, and resolves the decades-long search for CMEs beyond the sun."

“XMM-Newton现在正在帮助我们发现日冕物质抛射是如何因恒星而异的，这不仅对我们研究恒星和太阳很有趣，而且对我们寻找其他恒星周围的宜居世界也很有趣，”ESA XMM-Newton项目科学家Erik Kuulkers说。“它还展示了协作的巨大力量，这是所有成功科学的基础。这一发现是真正的团队努力，解决了数十年来寻找太阳以外日冕物质抛射体的问题。”

The fact that the CME was fast and dense enough to strip away a planetary atmosphere also adds additional information to the criteria that define what a habitable planet is.

使CME会剥离行星大气层的是其巨大的速度和密度，这一事实也为定义可居住行星的标准提供了额外的信息。

"This work opens up a new observational frontier for studying and understanding eruptions and space weather around other stars," Henrik Eklund, an ESA at the European Space Research and Technology Centre (ESTEC) in Noordwijk, The Netherlands, said. "We're no longer limited to extrapolating our understanding of the sun's CMEs to other stars. It seems that intense space weather may be even more extreme around smaller stars – the primary hosts of potentially habitable exoplanets. This has important implications for how these planets keep hold of their atmospheres and possibly remain habitable over time."

荷兰诺德韦克欧洲空间研究与技术中心（ESTEC）欧空局成员亨里克·埃克伦德（Henrik Eklund）表示：“这项工作为研究和了解其他恒星周围的喷发和空间天气开辟了一个新的观测前沿。”，“我们不再局限于将我们对太阳日冕物质抛射到其他恒星。似乎在较小的恒星周围，强烈的太空天气可能会更加极端——潜在可居住系外行星的主要宿主。这对这些行星如何保持大气层并可能随着时间的推移保持可居住性具有重要意义。”

Currently, to be considered habitable, a planet has to sit in the zone around its star that is neither too hot nor too cold to support liquid water, known as the habitable or "Goldilocks" zone. But, if the star at the heart of that zone is particularly active and is throwing out violent and frequent CMEs, not even a stable orbit in the Goldilocks zone will help it sustain an atmosphere, and thus the conditions needed for life to prosper.

目前，要被认为一颗可居住的行星必须位于其恒星周围既不可太热也不太冷而无法支持液态水的区域，即所谓的可居住区域或“金发姑娘”区域。但位于该区域中心的恒星表现得特别活跃，并且正在抛出迅猛而频繁的日冕物质抛射，那么即使是金发姑娘区域的稳定轨道也无法协助其保持大气层，从而维持生命繁荣所需的条件。

That is a significant discovery because red dwarf stars like this one are the most common stars in the Milky Way. Thus, more of these stars than was previously believed may be stripping their orbiting planets of their atmospheres.

这是重要的发现，因为像这样的红矮星是银河系中最常见的恒星之一。因此，比以前认为的更多的这些恒星可能会剥夺它们轨道行星的大气层。

Correction 11/12: The star is located around 130 light-years away, not 40 light-years away, and the estimated speed of the CME is only seen in 1 out of 2000 CMEs, not in 1 out of 20. This article has been updated to reflect that.

更正于11月12日有：这颗恒星位约130光年之外，而不是40光年之外，CME的估计速度只在2000个CME中的1个中看到，而不是20个中的1个。本文更新以反映这点。