数千颗奇怪的行星围绕着一个超大质量黑洞旋转

In the immediate vicinity of a supermassive black hole's event horizon, conditions are pretty wild. But travel a little farther out, and other objects can be snared in its gravitational influence - like the stars orbiting the supermassive black hole at the centre of our galaxy, Sagittarius A*.

在一个超大质量黑洞的视界附近，条件相当恶劣。但是，如果再往外走一点，其他物体就会受到它的引力影响——就像环绕银河系中心特大质量黑洞人马座a *的恒星一样。

According to a new paper, it's not just stars. There could be oodles of planets orbiting supermassive black holes, caught in their gravitational hold, but far out beyond immediate danger - up to tens of light-years away.

根据一篇新论文，不仅仅是明星。在超大质量黑洞的引力作用下，可能会有大量的行星绕其轨道运行，但它们远远超出了当前的危险范围——距离我们几十光年远。

Using planetary formation models, a team of astronomers led by Keiichi Wada of Kagoshima University in Japan have shown, for the first time, a new class of planets that can directly form around a black hole.

利用行星形成模型，由日本鹿儿岛大学的和田圭一(Keiichi Wada)领导的一组天文学家首次发现了可以直接围绕黑洞形成的一类新行星。

And these planets would not be subject to the same limitations as planets forming around a baby star.

而且这些行星不会受到与围绕小星星形成的行星相同的限制。

Our calculations show that tens of thousands of planets with 10 times the mass of the Earth could be formed around 10 light-years from a black hole, said astronomer Eiichiro Kokubo of the National Astronomical Observatory of Japan.

日本国家天文台的天文学家Eiichiro Kokubo说:“我们的计算显示，在距离黑洞约10光年的地方，可能会形成数万颗质量是地球10倍的行星。”

Around black holes there might exist planetary systems of astonishing scale.

“黑洞周围可能存在规模惊人的行星系统。”

Like baby stars, black holes can often be surrounded by a large, dense disc of dust and gas. In the case of a star, this rotating disc is left over from the matter that formed the star; out of that protoplanetary disc, planets can then form and continue spinning around their home star.

就像小恒星一样，黑洞经常会被一个巨大而稠密的尘埃和气体圆盘所包围。对于恒星来说，这个旋转的圆盘是由形成恒星的物质遗留下来的;在原行星盘之外，行星可以形成并继续围绕它们的母星旋转。

The fluffy dust aggregate that makes up the disc starts to cling together due to electrostatic forces, then collisions, and then gradually accumulating more and more grains until it's massive enough for gravitational forces to take over, et voilà - after a few million years, you have a planet.

由于静电力的作用，构成圆盘的蓬松的灰尘聚集在一起，然后碰撞，然后逐渐积累越来越多的颗粒，直到它的质量足够大，让重力来接管，瞧，几百万年后，你就有了一个行星。

Now, when it comes to supermassive black holes, their discs contain a lot more dust - up to a billion times more than a protoplanetary disc, according to the researchers. Similar planet formation dynamics are likely at play in the outer reaches of the black hole discs as you see in a protoplanetary disc.

现在，当涉及到超大质量黑洞时，它们的星盘包含更多的尘埃——根据研究人员的说法，是原行星星盘的十亿倍。类似的行星形成动力学很可能在黑洞盘的外围发挥作用，就像你在原行星盘中看到的那样。

It's even possible that black hole discs are, at great distances, more efficient at planet formation than protoplanetary discs. This is because the planet 'seeds' - called planetesimals - wouldn't be subject to a protoplanetary disc phenomenon called the radial drift barrier.

甚至有可能，在很远的距离上，黑洞盘比原行星盘更能有效地形成行星。这是因为行星的“种子”——即所谓的星子——不会受到一种叫做径向漂移障壁的原行星盘现象的影响。

According to dynamical modelling, this occurs when a planetesimal accumulates so much mass that its orbit is no longer stable, and it starts to rapidly migrate towards an accreting star, meeting its eventual demise.

根据动力学模型，当一个星子积累了如此多的质量以至于它的轨道不再稳定，它开始快速地向一个吸积恒星迁移，最终遭遇它的死亡。

In a disc around a black hole, the radial drift velocity would be negligible compared to the orbital velocity of the rotating disc. The inertia of this orbital velocity would keep the planetesimal from migrating towards the black hole in any meaningful time frame.

在黑洞周围的圆盘上，径向漂移速度与旋转圆盘的轨道速度相比可以忽略不计。这个轨道速度的惯性将使星子在任何有意义的时间范围内都不会向黑洞移动。

Planets also start to form in cooler regions of a protoplanetary disc, where the dust grains are coated with ice. In a disc around an active black hole, blasting radiation from the intense heat generated by the friction of the swirling gas falling into it, the outer regions could be protected from this radiation by the dust itself.

行星也开始在原行星盘的较冷区域形成，那里的尘埃颗粒被冰覆盖。在一个活跃的黑洞周围的圆盘中，由于旋转的气体落入黑洞时产生的摩擦产生了强烈的热量，从而产生了爆炸辐射，尘埃本身可以保护外围区域不受这种辐射的影响。

Because the dust is so dense, it would block the radiation, creating cool, planet-formation-safe pockets.

因为尘埃密度太大，它会阻挡辐射，形成凉爽的、对行星形成安全的口袋。

While the researchers' finding is tantalising, sadly we can't currently detect such black-hole-hosted planets. Nevertheless, this research could one day lead to an entire new way of discovering alien worlds - and they might be quite a sight to behold.

虽然研究人员的发现很诱人，但遗憾的是，我们目前还无法探测到这种黑洞行星。尽管如此，这项研究总有一天会带来一种发现外星世界的全新方式——它们可能会成为一道亮丽的风景线。

The research has been published in The Astrophysical Journal.

这项研究发表在《天体物理学杂志》上。