The Sun, Moon, and the planets formed from a huge spinning gas cloud that collapsed into a gyrating disc.
太阳、月亮和这些星球形成于倒塌进一个旋转盘状物的一团巨大旋转汽云。
They shunned the belief that there is a link between the alignment of the planets and events on the Earth.
他们回避了在行星的排列和地球上发生的事件之间有联系的看法。
Science fiction writers have long dreamed that humans might one day quit the earth to colonize other planets.
科幻小说作家们长期以来一直梦想着人类有一天可以离开地球移居到其它星球上。
They are aliens on other planets.
它们是其他星球上的外星人。
The planets revolve around the sun.
行星绕着太阳运转。
Hence, the Jovian planets are often called giants.
因此，木星行星通常被称为巨行星。
It is the gravitational interaction with planets, right?
这是引力与行星的相互作用，对吧？
If they were shadows of the planets, they would be circular, right?
如果它们是行星的影子，它们就会是圆形的，对吧？
In 1997, they saw evidence of planets near other stars like the sun.
1997年，他们发现了太阳等其他恒星附近有行星存在的证据。
By comparison, the terrestrial planets have meager atmospheres at best.
相比之下，类地行星最多只有稀薄的大气层。
Most known extrasolar planets reside in highly elongated, not circular, orbits.
大多数已知的太阳系外行星都居住在高度拉长而非圆形的轨道上。
Mercury is known to have a high density in comparison with other rocky planets.
众所周知，与其他岩石行星相比，水星的密度很高。
However, many of these planets are either too near to the star or too far away.
然而，这些行星中有许多都离恒星太近或太远。
The team found that at some positions in the disk, planets would be pushed inward.
这个研究小组发现在盘状物的某些位置上行星会被向内推。
No-one had found a way to calculate accurate distances to the planets from the Earth.
还没有人找到方法来计算从地球到行星的精确距离。
"Regions of outward migration allow planets and planetoids to survive, " Mac Low said.
麦克·劳说：“向外迁移的地区使行星和小行星得以生存。”
Since the earliest times, people have looked up at the stars, the moon and the planets.
自人类诞生之初起，人们就仰望星星、月亮和行星。
American scientists have been using instruments for years to look for earth-like planets.
美国科学家多年来一直在使用仪器寻找类地行星。
They will likely then travel close enough to neighboring planets to disturb their orbits also.
然后，它们很可能会飞得离邻近的行星足够近，从而扰乱它们的轨道。
However, unlike Jupiter, the terrestrial planets today are nearly void of light gases and ices.
然而，如今的类地行星与木星不同，几乎没有轻气体和冰。
Variations in the composition of the planets are largely responsible for the density differences.
行星构成成分的不同是造成密度差异的主要原因。
The terrestrial planets are mostly rocks: dense rocky and metallic material, with minor amounts of gases.
类地行星主要是岩石：密度大的石块和金属物质，同时会有少量的气体。
The absence of oxygen on other planets means that those planets lack an ozone shield to protect life forms against UV radiation.
其他行星上没有氧气，这意味着这些行星缺乏保护生命体免受紫外线辐射的臭氧层。
The nearly circular orbits of planets in our solar system led scientists to expect that planets around other stars would also reside in circular orbits.
在我们的太阳系中，行星的轨道几乎是圆形的，这使得科学家们预测，其他恒星周围的行星也会位于圆形轨道上。
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