| 1. | Planetologists believe comets are the oldest relics in the solar system .
行星学家们认为，彗星是太阳系中最古老的残余物。 |
| 2. | Perhaps at an early stage the solar system consisted of comet-sized objects .
也许，早期阶段的太阳系是由彗星那么大小的天体所构成的。 |
| 3. | Most stars probably have their quota of planets, meteorids, comets, and asteroids .
多数恒星也许还拥有若干行星、流星、彗星和小行星。 |
| 4. | The night sky is occasionally host to the transient visitors known as comets and meteors .
夜空有时还接待如彗星和流星那样的过路来访者。 |
| 5. | It was a comet, and maria had been the first person to see it and report on it .
它就是彗星，玛利是世界上第一个看到并报导了这颗星的人。 |
| 6. | If you are fortunate enough to see a comet, don't give it just a casual glance and then vanish indoors .
倘若你有幸看到彗星，不要随意扫上一眼就进到屋里。 |
| 7. | Scientists want to study comets because they may be the oldest objects in our solar system .
科学家之所以要研究彗星，是因为它们可能是太阳系中最古老的星球。 |
| 8. | In the far reaches of the solar system comets range from a few km to a few hundred km across .
在太阳系的广阔空间范围里，彗星的大小一般从几千米到几十万米。 |
| 9. | Many scientists believe that lunar craters were formed by the collision of meteors and comets against the moon .
许多科学家相信，月球坑穴是流星和彗星碰撞月球所造成的。 |
| 10. | Celestial mechanics enables astronomers to calculate the positions of the planets at any time in the post or future and to predict the movements of comets .
天体力学使文学家能计算出行星在过去或将来任何时候的位置，并能预报彗星的运行位置。 |
