太陽系中你不知道的10個怪異物體(下)
5.2008 KV42
5.2008 KV42Why do so many astronomical objects have annoying names? Luckily, this comet was nicknamed "Drac," after Dracula—due to his ability to walk on walls—which is much easier to say. What does walking on walls have to do with a comet? Well, Drac was the first trans-Neptunian object discovered to orbit the Sun backward—albeit slowly, taking 306 years. (We still don't quite see the link to walking on walls, either.) While there were already a few objects known to orbit the Sun backward—you may have heard of Halley's Comet—they get very close to the Sun in their orbit. Drac, however, never gets any closer than roughly 20 times the distance from the Sun to Earth—equal to the orbit of Uranus. This means that the comet could be the missing link between objects like Halley's Comet and other debris in the far-out Oort Cloud of comets past Pluto, helping to explain their formation, which is currently a mystery to science.
看到這一名字您是不是在想爲什麼天體就不能好好取名字呢？還好這顆彗星有個更簡單的別名——德拉庫彗星。這個名字來源於德拉庫拉星體。這是第一個被發現的圍繞太陽逆轉的外海王星天體，儘管它速度很慢——306年才能轉一圈。（但我們還是不知道這和能在牆上行走有什麼關係）。其實現在已經發現有好幾個天體圍着太陽逆行——比如哈雷彗星——它們的運轉軌道和太陽都離得非常近。但德拉庫到太陽的距離卻非常遠——甚至超過地球到太陽的距離的20倍，和天王星的運行軌道相近。這意味着這顆彗星可能是類似哈雷彗星這樣的天體與冥王星附近的歐特星雲中天體碎片的失聯環節，這對研究那些天體碎片的形成過程具有重要意義。可這至今還是科學上的一個未解之謎。
There are many ideas out there attempting to explain why the orbit of Drac is so unlike almost all others. One of the most interesting prospects is that it might not have formed together with our solar system at all—otherwise it would orbit in the same direction as everything else. It is entirely possible that the comet could have gotten trapped in our solar system from interstellar space, providing us with an unprecedented amount of information about the cosmos.
有許多學說都嘗試解釋爲什麼德庫拉的公轉方式如此與衆不同。其中最有趣的一個設想是德庫拉可能根本就不是隨着太陽系而形成的，否則它的運行方向應該和其他衛星一樣。這顆彗星完全有可能是突然"闖進來"的，這能給我們帶來大量關於宇宙的信息。
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4.特里同
While it isn't a household name, some of you have probably heard of Triton before. But hear us out—there is more than meets the eye with this fantastic specimen. Comprising more than 99 percent of all the mass known to orbit Neptune, it's as if all the gas giant's awe was condensed into one moon. As shown by the Voyager 2 probe in 1989, Triton is rare among known moons in that it is geologically active: Volcanoes pepper the surface, but they do not spew ash and lava when they erupt, like those on Earth. Instead, they spew water and ammonia.
雖然特里同並不是個家喻戶曉的名字，但還是有人聽過它的。您請稍安勿躁，聽我們說完，這個夢幻般的星球絕不僅僅是隻能滿足視覺感受這樣簡單。特里同一個星體的質量就佔據了海王星所有衛星質量總和的99%以上，彷彿所有能在氣體巨星上看到的壯觀景象都聚集在一顆衛星上。1989年"航行者2號"發回的探測數據顯示，特里同和其他已知衛星不一樣，雖然它也是遍地火山 ，但噴發的是水和氨而不是火山灰和熔岩。Being just a bit smaller than our own Moon, Triton is the only large moon in the solar system to orbit backward. Also, being one of the largest known moons in our solar system—larger than Pluto—it has just enough gravity to support a thin atmosphere. Seriously thin. With surface air pressure 50,000 times lower than that of Earth, you couldn't fly a kite on Triton's surface. Yet, incredibly, Voyager 2 photographed clouds flying just a few kilometers above the lly, Triton is one of the most reflective objects known to science, reflecting 60–95 percent of all light that hits it. To put that into perspective, the Moon—which is able to cast shadows on Earth at night—reflects only 11 percent.
特里同僅比我們的衛星（月亮）小一點，是太陽系中唯一一顆與主星旋轉方向相反的大衛星。此外，作爲太陽系中已知的大衛星（大於冥王星），它有足夠的重力來支撐稀薄的大氣層——真的非常薄。特里同的表面氣壓是地球氣壓的1/50000，你根本無法在那裏放風箏。但不可思議的是，旅行者2號還是拍攝到了在它地表幾千米之上的雲層。最後，特里同是科學界公認的反射能力最強的天體之一，反射率約爲60%~95％。爲了正確理解這一概念，我們以月球爲例說明，月球的反射率只有11%。rn's Extra Ring
3.土星巨型外環
We've mentioned Saturn a few times so far, but it is certainly an incredibly interesting place. While the planet is known for its staggering ring system, only recently did we find out just how far it extended out into space. In 2009, we discovered an enormous ring around Saturn, the farthest and largest band around the ringed world. The ring is tilted 27 degrees from the main rings and starts roughly 128 times the planet's radius from its surface, extending to 207 times its radius into space. It is so diffuse that it can only be detected in infrared, but it may be the reason behind the two-toned moon, Iapetus.
我們已多次提到土星，因爲它真的是一個非常有趣的地方。雖然我們早已對這個星球驚人的外環系統有所瞭解，可最近才發現這個環向太空延伸得有多遠。2009年，我們發現了土星的巨大外環，它是宇宙中已知最大的、延伸得最遠的環，該環與主環成27度，分佈在距土星表面128倍半徑到207倍半徑之間。雖然它如此彌散，只能被紅外線檢測到，但它很可能是雙色衛星——伊阿珀託斯形成的原因。Saturn's moon Phoebe orbits within the ring and at the same inclination, so it is very likely that it is the culprit. Dust disperses from Phoebe and falls onto the larger Iapetus, which orbits on the edge of this colossal new ring. Every time Iapetus passes through it, matter collects on its equator. After hundreds of thousands of years, this matter seems to have built up, creating the moon's striking appearance. Now it is just a question of whether it is black with white stripes or white with black stripes.
土星的菲比衛星的運行軌道也在該環內，並且傾斜角度也相同，所以它很可能也是伊阿珀託斯呈現雙色的另一個原因。宇宙塵埃從菲比衛星散射出來並落到更大的伊阿珀託斯星周圍。而伊阿珀託斯在這巨大新環的邊緣運轉，每次伊阿珀託斯經過菲比衛星，這些物質就在伊阿珀託斯的赤道上不斷積累。經過成千上萬年，這些堆積的物質創造了壯觀的外環。現在的問題是，它到底是黑色參雜白色條紋還是白色參雜黑色條紋呢？。ese Moons
2.暹羅雙星
The moons Janus and Epimetheus are known as the "Siamese moons," because they share the same orbit and are separated by only 50 kilometers (31 mi)—that's less than the radius of the moons themselves. Because of this, they are locked in a gravitational tango that causes them to literally swap places every four years. Due to their complex relationship, they will never crash into each other.
雅努斯和厄庇墨透斯是人們熟知的"暹羅雙星"，它們在同一軌道上運行而且僅僅相隔50千米（31英里）——這距離比它們本身的半徑還要短。它們複雜的關係使它們永遠不可能互撞，也正因爲如此，它們才能在重力影響下每四年跳一次探戈，交換一次位置。Originally, scientists were puzzled as to why data did not match their expectations of the moon they had named "Janus." In 1978, 12 years after the discovery of their common orbit, we realized that what we had called Janus was actually two separate moons. This was confirmed by the Voyager flyby in 1980. Interestingly, a faint ring of dust is present in the region of their orbits. This suggests that the two moons were once a single larger one that has since broken up, leaving behind trace amounts of rubble.
起初，科學家們很困惑爲何他們所測出的數據和它們所取的名字並不契合，"Janus"在古羅馬語裏是雙面神的意思。而在1978年，也就是發現兩星共行同一軌道的12年後，我們發現這並不是"雙面"，而是"雙星"，這也在1980年被"航行者號"近地探測所證實。有趣的是，該軌道上有一層淡淡的灰塵，這意味着這兩個衛星原本是合體的一個大衛星，分裂後留下了大量的碎片。thne
1.克魯坦
After taking a look at stuff way out there in our solar system, let's head home to Earth and discuss the largely disputed matter of our planet's second moon. Since 1846, astronomers have been searching for a second moon of Earth. Frederic Petit was the first to claim he had found one. He proposed that it orbited Earth in less than three hours at just 11 kilometers (7 mi) above our planet's surface. Ever since, many other astronomers have claimed to find a second moon—but to no avail. However, there is one weird exception.
讓我們把目光從太陽系別的天體上稍稍收回來，重返地球家園來討論一下我們飽受爭議的第二衛星（第一衛星是月亮）。從1846年以來，天文學家就着力尋找地球的第二個衛星。弗雷德裏克是第一個聲稱自己找到第二衛星的人。他認爲這顆衛星圍繞地球運行，運行週期不足三小時，距離地球表面最近距離爲11千米（7英里）。從那以後，很多天文學家也都聲稱自己發現了第二衛星——但都是徒勞的。不過，也有一個例外。Cruithne is an alien asteroid that orbits the Sun in 364 days, with perfect resonance to that of Earth. This means that, for a short time every year, the 5-kilometer (3 mi) asteroid is part of the Earth system. It reaches its closest point to Earth every November. Technically, it does not count as a moon, since it leaves Earth. But it's still nice to think that every year, an alien object comes to visit.
克魯坦是一顆外來小行星，繞太陽公轉週期爲364天，與地球有着完美的共振。這意味着，在每年的一段短暫的時間裏，這顆5千米（3英里）的小行星是地球系統的一部分。每年11月它和地球距離最近。確切來說，既然它能離開地球，那麼它就不能被看作是地球的衛星。但是想想每年都有一個外來物體光臨地球。這也是一件很美好的事情。審校：哈利 來源：前十網
