天文学家发现了地狱般的火山外星系的迹象

天文学家发现了地狱般的火山外星系的迹象

Given the extravagant profusion of moons in our own Solar System, it seems likely that there are way more exomoons out there in the Universe than there are exoplanets. We're yet to conclusively find one - but astronomers just found a signal that could mean the presence of an exomoon.

考虑到太阳系中大量的卫星，似乎宇宙中有比外行星更多的外行星。我们还没有最终找到一个——但天文学家刚刚发现了一个信号，这可能意味着外行星的存在。

Not just any exomoon, either, but something akin to a jacked-up version of the Jovian moon Io, the most volcanically active object in the Solar System.

不仅是任何外行星，而是类似于木星的卫星木卫一的升级版，木卫一是太阳系中火山活动最活跃的天体。

And we really do mean jacked. Not only would the exomoon itself be covered in volcanoes spewing lava, it would be orbiting a hot planet - WASP-49b, a massive gas giant planet known as a hot Jupiter, hurtling around yellow dwarf star WASP-49 once every 2.8 days.

我们的意思是被劫持。这颗外行星不仅会被喷涌熔岩的火山所覆盖，还会围绕着一颗热行星WASP-49b运行。WASP-49b是一颗巨大的气态巨行星，被称为热木星，每2.8天绕黄色矮星WASP-49旋转一次。

"It would be a dangerous volcanic world with a molten surface of lava, a lunar version of close-in Super Earths like 55 Cancri-e," said astrophysicist Apurva Oza of the Physics Institute of the University of Bern.

伯尔尼大学物理研究所的天体物理学家阿普尔瓦·奥扎说：“这将是一个危险的火山世界，熔岩的熔融表面，类似于月球上的近地天体，如55 Cancri-e。”

But don't go packing your lava suits just yet. The team didn't detect the exomoon directly. They have inferred it exists based on data from the planet itself - from stuff detected in its upper atmosphere.

但现在不要去收拾你的熔岩服。研究小组没有直接探测到外行星。他们根据行星本身的数据推断出它的存在，这些数据来自于在其高层大气中探测到的物质。

When a paper describing the atmosphere of WASP-49b was published in 2017, researchers noted the presence of a thick layer of sodium at unusually high altitudes free of clouds. This sodium layer made Oza's international team look more closely.

2017年，当一篇描述WASP-49B大气的论文发表时，研究人员注意到在异常高的高度上存在着一层厚厚的钠，没有云层。这一钠层使奥扎的国际团队看起来更近。

"The neutral sodium gas is so far away from the planet that it is unlikely to be emitted solely by a planetary wind," he said.

他说：“中性的钠气体离地球太远，不太可能仅仅由行星风排放。”

We know, based on observations closer to home, that volcanic activity on Io produces pretty hefty amounts of potassium and sodium (among a few other things). These do not cling in significant quantities to the moon, but get swept up into Jupiter's complex magnetosphere, resulting in a torus of material ringing the planet.

我们知道，根据离地球较近的观测，木卫一上的火山活动产生了相当多的钾和钠(以及其他一些物质)。这些物质并不会大量地附着在月球上，而是会被卷入木星复杂的磁层中，形成一个环绕着行星的物质环面。

We also know that, without the intense gravitational interplay between Io and Jupiter generated by the moon's elliptical orbit - the varying tidal forces that create friction and thus heat in the moon - it would not be volcanically active.

我们还知道，如果没有月球椭圆轨道产生的木卫一和木星之间的强烈引力相互作用——月球上产生摩擦和热量的潮汐力各不相同——它就不会有火山活动。

In 2006, a different team of researchers extrapolated that the presence of a torus of material around a planet could imply the presence of a moon or other orbiting body.

2006年，另一组研究人员推断，行星周围存在一个物质环面，可能意味着存在一个月球或其他轨道物体。

So, the team crunched some numbers. And they found that a volcanically active exomoon could actually release more potassium and sodium than the planet it orbits.

所以，小组计算了一些数字。他们发现，火山活动的太阳系外行星，实际释放的钾和钠比它所运行的行星多。

The sodium and potassium around WASP-49b, in the quantities and at the strange altitude detected, Oza's team concluded, could have plausibly been spewed out by a volcanic hell-moon. But it's also plausible that other processes or phenomena are responsible - a ring of ionised gas, for example.

奥扎的研究小组得出结论，WASP-49b周围的钠和钾的含量，以及在这个奇怪的高度所探测到的含量，都有可能是由一个火山地狱般的月亮喷发出来的。但也有可能是其他过程或现象造成的，比如电离气体环。

Once again, more observation would help find answers - analysing the planet's spectrum in greater detail. Sodium and potassium lines on the spectrum are both very strong; by searching more closely, the researchers hope to find the weaker signals of other volcanic volatiles in the planet's atmosphere, such as sulphur and oxygen.

再一次，更多的观察将有助于找到答案——更详细地分析行星的光谱。钠和钾的光谱线都很强;通过更仔细的搜索，研究人员希望能找到地球大气中其他火山挥发物质的微弱信号，如硫和氧。

In addition, it provides yet another excellent reason to probe the atmospheres of exoplanets - a task at which we hope the next generation of telescopes will excel.

此外，它还为探测系外行星的大气层提供了另一个很好的理由——我们希望下一代望远镜，能够在这项任务上取得卓越的成就。

"While the current wave of research is going towards habitability and biosignatures, our signature is a signature of destruction," Oza said. "The exciting part is that we can monitor these destructive processes in real time, like fireworks."

奥扎说:“虽然目前的研究浪潮正在向宜居性和生物特征发展，但我们的特征是破坏的特征。令人兴奋的是，我们可以实时监控这些破坏性的过程，就像烟花一样。”

The research has been accepted into The Astrophysical Journal.

这项研究已被《天体物理学杂志》接受。