數(shù)千顆奇怪的行星圍繞著一個超大質(zhì)量黑洞旋轉(zhuǎn)

數(shù)千顆奇怪的行星圍繞著一個超大質(zhì)量黑洞旋轉(zhuǎn)

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*.

在一個超大質(zhì)量黑洞的視界附近，條件相當惡劣。但是，如果再往外走一點，其他物體就會受到它的引力影響——就像環(huán)繞銀河系中心特大質(zhì)量黑洞人馬座a *的恒星一樣。

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.

根據(jù)一篇新論文，不僅僅是明星。在超大質(zhì)量黑洞的引力作用下，可能會有大量的行星繞其軌道運行，但它們遠遠超出了當前的危險范圍——距離我們幾十光年遠。

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，由日本鹿兒島大學的和田圭一(Keiichi Wada)領(lǐng)導的一組天文學家首次發(fā)現(xiàn)了可以直接圍繞黑洞形成的一類新行星。

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

而且這些行星不會受到與圍繞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.

日本國家天文臺的天文學家Eiichiro Kokubo說:“我們的計算顯示，在距離黑洞約10光年的地方，可能會形成數(shù)萬顆質(zhì)量是地球10倍的行星。”

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

“黑洞周圍可能存在規(guī)模驚人的行星系統(tǒng)。”

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.

就像小恒星一樣，黑洞經(jīng)常會被一個巨大而稠密的塵埃和氣體圓盤所包圍。對于恒星來說，這個旋轉(zhuǎn)的圓盤是由形成恒星的物質(zhì)遺留下來的;在原行星盤之外，行星可以形成并繼續(xù)圍繞它們的母星旋轉(zhuǎn)。

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.

由于靜電力的作用，構(gòu)成圓盤的蓬松的灰塵聚集在一起，然后碰撞，然后逐漸積累越來越多的顆粒，直到它的質(zhì)量足夠大，讓重力來接管，瞧，幾百萬年后，你就有了一個行星。

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.

現(xiàn)在，當涉及到超大質(zhì)量黑洞時，它們的星盤包含更多的塵埃——根據(jù)研究人員的說法，是原行星星盤的十億倍。類似的行星形成動力學很可能在黑洞盤的外圍發(fā)揮作用，就像你在原行星盤中看到的那樣。

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，在很遠的距離上，黑洞盤比原行星盤更能有效地形成行星。這是因為行星的“種子”——即所謂的星子——不會受到一種叫做徑向漂移障壁的原行星盤現(xiàn)象的影響。

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.

根據(jù)動力學模型，當一個星子積累了如此多的質(zhì)量以至于它的軌道不再穩(wěn)定，它開始快速地向一個吸積恒星遷移，最終遭遇它的死亡。

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.

在黑洞周圍的圓盤上，徑向漂移速度與旋轉(zhuǎn)圓盤的軌道速度相比可以忽略不計。這個軌道速度的慣性將使星子在任何有意義的時間范圍內(nèi)都不會向黑洞移動。

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.

行星也開始在原行星盤的較冷區(qū)域形成，那里的塵埃顆粒被冰覆蓋。在一個活躍的黑洞周圍的圓盤中，由于旋轉(zhuǎn)的氣體落入黑洞時產(chǎn)生的摩擦產(chǎn)生了強烈的熱量，從而產(chǎn)生了爆炸輻射，塵埃本身可以保護外圍區(qū)域不受這種輻射的影響。

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

因為塵埃密度太大，它會阻擋輻射，形成涼爽的、對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.

雖然研究人員的發(fā)現(xiàn)很誘人，但遺憾的是，我們目前還無法探測到這種黑洞行星。盡管如此，這項研究總有一天會帶來一種發(fā)現(xiàn)外星世界的全新方式——它們可能會成為一道亮麗的風景線。

The research has been published in The Astrophysical Journal.

這項研究發(fā)表在《天體物理學雜志》上。