地球离最近的恒星大约为4光年。
银河系由1千亿颗恒星组成。
北极星似乎由一颗脉动的恒星衍变而来。
The Pole Star appears to be changing from a star that pulsates.
这些恒星一定形成于100亿至150亿年前。
我们可以期待在一颗恒星位置上的一个微小晃动。
这个价值6.17亿美元的人造卫星将研究宇宙中活动最剧烈的恒星所发出的辐射能。
The $617 million satellite will study energy radiation from the most violent stars in the universe.
它使得分析恒星发出的光成为可能。
It makes it possible to analyze the light emitted from stars.
首先，天文学家要寻找一颗恒星。
这三颗尖尖的恒星位于我们的银河系。
它是格利泽581g，它在一颗恒星附近。
视差原理可以扩展到测量地球到恒星的距离。
The parallax principle can be extended to measure the distances to the stars.
然而，这些行星中有许多都离恒星太近或太远。
However, many of these planets are either too near to the star or too far away.
我们在地球上看到的其实是来自恒星的电磁辐射。
What we are seeing from earth is actually electromagnetic radiation that's coming from stars.
他突然想到，烟火也许可以有效地展现恒星是如何形成的。
It occurred to him that fireworks might provide an effective way of demonstrating how stars were formed.
即使是我们银河系附近的恒星发出的光，也无法与之抗衡。
Light from stars, even nearby in our own galaxy, doesn't stand a chance against that.
当天文学家发现了这颗恒星，他们就会观察它周围的行星。
When astronomers have found the star, they look at the planets around it.
它来自射手座的方向；那个方向最近的恒星距离220光年。
It came from the direction of Sagittarius; the nearest star in that direction is 220 light-years away.
如果你观察其他恒星的光谱，你会发现它们的颜色是一样的。
If you were looking at the spectrum of some other star, the colors would be the same.
近年来，天文学家已经发现了近400颗新的有行星的恒星。
In recent years, astronomers have found nearly 400 new planets with stars.
1997年，他们发现了太阳等其他恒星附近有行星存在的证据。
In 1997, they saw evidence of planets near other stars like the sun.
光谱显示，这些恒星在膨胀的红巨星阶段肯定曾经吞没过这些行星。
The spectra show that the stars must have swallowed such planets during their expansive, red-giant stage.
如果该恒星的旋转加快仅仅20%，那么离心力就会将其甩得粉碎。
If the fixed star spun just 20% faster, the centrifugal force would fling it apart.
大体上，所有靠近地球的这些物体所反射的光都比来自恒星的要亮。
Basically the light bouncing off all these objects close to earth is brighter than what's coming from the stars.
在光学天文学中，在用望远镜观察恒星时，我们依靠的是可见光波。
In optical astronomy, using a telescope and observing the stars that way, we rely on visible light waves.
相反，它们之所以是黑暗的，是因为星际尘埃将恒星隐藏在它的后面。
Rather, they are dark because of interstellar dust that hides the stars behind it.
我们怎么知道地球是一个更小的球，绕着其中一颗恒星——太阳转呢？
How do we know that the Earth is a smaller ball turning around one of those stars, the Sun?
其母体恒星就像是一个红色的小矮人——比起太阳来实在是又小又模糊。
Its parent star is a red dwarf--a far smaller and fainter object than the sun.
还有一个问题：在与恒星相撞之前，是什么阻止了这颗行星继续螺旋运动？
Another question remains: what prevents the planet from continuing its spiral until it collides with the star?
行星被认为是由围绕恒星旋转的气体和尘埃组成的圆盘中的粒子累积而成。
Planets are believed to emerge from the accretion of particles in a disk of gas and dust as they whirl around the star.
最后，科学家测量了由于行星的引力拖拉而产生的恒星摆动，这就是径向速度。
Finally, scientists measure the star's wobble due to the planet's gravitational tug, known as the radial velocity.
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