周期彗星 meaning in English
periodic comet
Examples
- Overlap between the second hand and minute hand , or the 11th overlap between the minute hand and hour hand , which is 12 hours later . actually it is easy to see this must be one of the answers . but it is a bit surprising that they simply do not overlap at other times
天文学家斯特格及奥尔特在1950年提出在太阳以外五万个天文单位的地方，有一个包围著太阳系，以太阳为中心旋转的云团，我们所见的长周期彗星，就是从这个彗星云又称为奥尔特云而来，估计那里有1 , 000亿颗彗星，其总质量比地球质量小，绕太阳公转一周需时数百万年。