In Earth's formative years, it was hit by thousands of comets like this.
在地球的最初岁月中，它曾被成千上万个这样的彗星撞击。
It could have come from the impacts of comets, for instance, or from within the Moon.
这些水可能是来自撞击的彗星，或来自月球内部。
The big planet throws a lot of comets out of the solar system, but it also throws them in.
这个大魔头向太阳系外扔了很多扫帚星，但又把它们引向了太阳系内部。
Edmond Halley, English astronomer and mathematician, renowned for studies of comets, was born in London.
以研究彗星称著的英国天文学家、数学家埃德蒙·哈雷生于伦敦。
This radiation pressure is thought to shape the tails of comets and is useful for pushing solar sails in space.
这种辐射压力被认为是彗尾形成的原因。 另外，它也是太阳帆在太空中前进的动力来源。
There is statistically significant evidence that this concentration of comets could be caused by a companion to the Sun.
他说，「大量统计证据表明，密集的彗星事件应该是由一颗太阳的伴星导致的。
Meteors, also called shooting stars, normally begin as bits of dust from the tails of comets or even small pieces chipped off asteroids.
流星群，也称流星雨，通常是慧星慧尾的尘埃或者从小行星上脱落的小块物质引起的。
The rings—there are thousands—are made up of billions of ice and rock particles, thought to be pieces of comets, asteroids, or shattered moons
这些环，有成千上万个，是由数十亿个冰和岩石的粒子所组成，这些粒子被认为是彗星、小行星和粉碎卫星的碎片。
Their explanation: a faint, far-off companion star to the Sun was sending down a rain of comets when it reached just the right point in its orbit.
他们的解释是这样的：遥远的地方，太阳有一颗微弱的伴星，当它到达轨道的某个定点时，就会产生大量彗星。
Quite a large number of comets are discovered every century, but most of them are extremely faint objects, far below the limits of the unaided eye.
每一个世纪都发现相当多的彗星，但大多数彗星都是非常微弱的天体，远不能为肉眼所见。
One leading theory: it came from a fusillade of comets that came screaming back in toward the sun a half-billion years or so after our planet formed.
有一种前沿理论认为：这些水是地球形成约5亿年之后，一连串呼啸撞向太阳的彗星所带来的。
The researchers say that there remains the possibility that other ancient sightings of comets could be uncovered from Chinese and Babylonian records.
研究人员说，人们还是有可能从中国和巴比伦的记录中，发现其他古人观测哈雷彗星的描述。
Note: Since astronomers have not fully understood the mechanism account for the brightening of comets, they can only predict by referring to past comets.
注：由于天文学家还未完全掌握彗星增光的机制，因此只能参考过去其他彗星的情况作出预报。
Every so often a comet gets flung out of the Oort Cloud, a swarm of comets on the fringes of the solar system, and gets close enough to Earth for us to see it.
经常有彗星被甩出奥尔特云(在太阳系边缘的彗星群)，并靠近地球到肉眼可以观测的距离。
Who, by vigor of mind almost divine, the motion and figure of the plants, the paths of comets, and the tides of the seas first demonstrated. the epitaph of Sir I.
靠着他近乎神圣的智力，行星的运动和轮廓，彗星的轨道，大海的潮汐第一次得到了论证。
It was learned that in the world of comets, the most famous is Halley's, and one of the four major meteor showers is from Aquarius, with its parent comet Halley's comet.
据介绍，在彗星世界里，最著名的就是哈雷彗星了，四大流星雨之一的宝瓶座流星雨的母体彗星就是哈雷彗星。
The cloud starts from a point about 93 billion miles from the Sun and stretches for around three light years and contains billions of comets, most of them small and hidden.
这个云团从距离太阳930亿英里外的一个点扩展到大约三光年的规模，同时包含了数以亿计的彗星，其中大部分彗星很小，而且是隐藏的。
Most of it is still there, frozen solid in, among other things, the rings of Saturn, Jupiter's moon Europa, the bodies of Neptune and Uranus and billions upon billions of comets.
这些水分至今还以冰冻的形式存在于土星环，木星的卫星欧罗巴，海王星、天王星以及数以十亿计的彗星之中。
We can see a number of comets with the naked eye when they pass close to the sun because their comas and tails reflect sunlight or even glow because of energy they absorb from the sun.
很多彗星接近太阳时，我们可以用肉眼看见，因为它们的彗发和彗尾可以反射阳光，甚至因为受阳光激发而自发光。
The comet currently headed for the sun may be part of the so-called Kreutz group of comets, which are known for having orbits that bring them within a few hundred thousand miles of the sun.
这颗冲向太阳的彗星可能是所谓的克鲁兹彗星家族的一员，这个彗星家族以其特殊的运行轨道而闻名于世，该轨道会将其带入太阳附近。
Brian explains how its greatest power, gravity, reaches out for hundreds of billions of kilometres, where the lightest gravitational touch encircles our solar system in a mysterious cloud of comets.
布莱恩解释了它最大的权力，重力，达到数千亿公里，轻的重力碰环绕太阳系的彗星的神秘的云。
Brian explains how its greatest power, gravity, reaches out for hundreds of billions of kilometres, where the lightest gravitational touch encircles our solar system in a mysterious cloud of comets.
布莱恩解释了如何最大的动力，重力，达到了对公里，其中最轻的引力触摸包围在一个神秘的彗星云太阳系千亿。
Roids are, for the most part anyway, they are just smaller bits of asteroids and comets.
在很大程度上，Roids只是小行星和彗星的小碎片。
The solar system also has two analogous classes of objects, smaller than planets—namely, asteroids and comets.
太阳系也有两类类似的物体，比行星还小——即小行星和彗星。
We think meteors that crashed into the moon or tails of passing comets may have introduced water molecules.
我们认为，撞击月球的流星或经过的彗星尾巴可能会留下一些水分子。
Soaring through the moonlight with Ellen in his arms, the pair of them shooting like comets into eternity while the clock in the parlor stops.
抱着埃伦在月光中飞翔，他们像彗星一样射入永恒，客厅里的钟停了。
Let's continue our discussion now by talking about orbits, especially those of the so-called periodic-orbit comets.
现在我们继续讨论，谈谈轨道，特别是那些所谓的周期轨道彗星。
Let's continue our discussion now by talking about orbits, especially those of the so-called periodic-orbit comets.
现在我们继续讨论，谈谈轨道，特别是那些所谓的周期轨道彗星。
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