When a comet orbits the Sun, the ice on it turns to gas, dislodging dust and gravel mixed in.

当彗星绕太阳公转时，它上面的冰会变成气体，把混合在一起的尘埃和砾石带走。

Presumably, supermassive black holes have stars, planets, asteroids and comets orbiting around them.

据推测，超大质量黑洞有恒星、行星、小行星和彗星围绕它们运行。

Now, this comet orbits the sun in such a way that it appears near the Earth every 75 years.

现在，这颗彗星绕太阳公转，每 75 年在地球附近出现一次。

Some believe that there are a number of large comets or dust orbiting the star while some actually think that there could be an alien race using advanced technology to siphon energy from it.

一些人认为有许多大彗星或尘埃围绕着恒星运行，而另一些人实际上认为可能有一个外星种族使用先进技术从它身上吸取能量。