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Astronomers have found a giant planet orbiting so close to its parent star that it's bound to spiral inward to its doom or else be ripped to shreds by the star's gravity. Either way, the planet called WASP-18b should provide astronomers with a mother lode of data about the delicate gravitational balancing act that affects all solar systems. |
天文学家们发现了一颗巨大的行星在很近的距离上围绕着其主恒星旋转，该行星正在盘旋着向内靠拢，注定要走向灭亡，或者要被主恒星的引力撕成碎片。不管是哪一种下场，这颗叫做“WASP-18b”的行星可以为天文学家们提供丰富的资料来源，使他们了解影响所有恒星系统的微妙的引力平衡作用。 |
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Stars and their planets can influence one another in subtle but inevitable ways. Even though Jupiter orbits about 500 million kilometers away from our sun, for example, the planet's huge mass can shift the sun's center of gravity by more than 10,000 kilometers, enough to possibly reveal the planet's presence to alien astronomers. The moon's pull on Earth raises and lowers sea levels in the form of tides. And conversely, Earth's gravity has slowed the moon's rotation so that it always presents the same face to its parent planet. |
恒星及其行星以一种微妙而必然的方式产生相互影响。例如，尽管木星在大约5亿公里之外围绕着太阳旋转，但该行星的巨大质量可以使太阳的引力中心产生1万多公里的偏差，足以向太阳系以外的天文学家展示该行星的存在。月球对地球的引力使海平面时升时降，表现形式为涨潮和退潮；反过来，地球的引力减慢了月球的自转速度，结果月球总是将其相同的一面展现给地球。 |
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Now researchers have found an extreme version of tidal forces at work. WASP-18b is roughly 10 times the mass of Jupiter, and it orbits only about 3 million kilometers from its star. WASP-18b, which was discovered with twin telescopes located in the Canary Islands and South Africa, is located about 400 light-years away in the constellation Phoenix. |
现在，研究人员发现一种极端形式的潮汐力在起作用。行星WASP-18b大约是木星的10倍，它在距其主恒星仅约300万公里的轨道上运行。WASP-18b位于大约400光年之外的凤凰座，是利用座落在加那利群岛和南非的一对望远镜发现的。 |
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WASP-18b and its star are so close to each other that it takes the planet, which is described in tomorrow's issue of Nature, less than a day to complete a revolution. As it orbits, WASP-18b drags bulges tens of kilometers high around the star's equator, making it spin faster. Those same forces also cost the planet its angular momentum, pulling it inward, eventually to the point where it will smash into the star's surface. Or perhaps it will be shredded to form a Saturn-like ring system. In either case, WASP-18b appears doomed to die within half a million years. |
研究人员在明天出版的《自然》杂志上描述道：行星WASP-18b距其主恒星非常近，仅用不到一天的时间就绕行一周。在做环绕运行时，WASP-18b的引力使主恒星的赤道周围隆起高达几十公里，并使主恒星的自转加速。这种相互作用使得该行星的角动量减小，因而不断向内靠拢，最终会撞入恒星的表面。或者，该行星也可能会被撕碎，形成象土星那样的光环系统。不管属于哪一种情况，WASP-18b似乎在50万年以内注定要灭亡。 |
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Or maybe not. Astronomer and co-author Andrew Collier Cameron of the University of St. Andrews in Fife, U.K., says there could be a third alternative: Some as-yet-unknown manifestation of tidal forces could prolong the planet's life by as much as 500 million years. That's because the close and fierce interaction between two large and essentially gaseous bodies could produce turbulence or other effects that could somehow cancel out WASP-18b's orbital deterioration. Astronomers may know whether that's happening within a decade or so, Collier Cameron says. By then, they will have collected enough data to determine whether WASP-18b's orbit has degraded and by how much. If WASP-18b somehow escapes imminent destruction by tidal forces, then astronomers will know that "our understanding of orbital dynamics, particularly tidal interactions, needs revision," says lead author Coel Hellier of Keele University in the United Kingdom. |
或者，也有可能不会灭亡。该研究的发起人之一、英国法夫市圣安德鲁斯大学天文学家安德鲁·科利尔·卡梅伦说，可能存在第三种情况：到目前为止仍不为人所知的某种潮汐力现象，可能会将该行星的寿命延长达5亿年之久。这是由于两个本质为气态的大型天体在近距离上发生剧烈的相互作用，这种作用会产生动荡或其他效应，也许会莫名其妙地修正WASP-18b走形的轨道。卡梅伦说，在十年左右的时间内，天文学家们可能会知道是否正在发生上述情况。到那个时候，他们将收集到足够的资料来确定WASP-18b的轨道是否发生了退化变形，以及在多大程度上发生了变形。“如果WASP-18b以某种方式靠潮汐力逃脱了即将灭亡的命运，那么天文学家们将会认识到我们对轨道动力学的理解需要改变了，特别是对潮汐作用的理解更需要改变，”该研究的首要发起人、英国基尔大学的科尔·赫利尔说。 |
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"It's the find of a lifetime," says astronomer Douglas Hamilton of the University of Maryland, College Park. "The beauty of this discovery is that we will be able to know [how WASP-18b will meet its end] within 5 to 10 years," Hamilton says. "I think that it could go either way--which makes it very exciting." |
“通常，这需要用一生的时间去发现，”马里兰大学帕克分校的天文学家道格拉斯·汉密尔顿说。“该发现的魅力在于：在5至10年之内，我们将能够知道WASP-18b是否会灭亡，”汉密尔顿说，“而我认为，两种可能性都有，这使得该行星非常令人激动。” |
