光辉的太阳上面常常出现黑色的斑点,这种斑点叫做“黑子”。黑子有时候单独存在,有时候成双结对,有时候形成一群。大黑子的中心部分总是比较黑一些,叫做“本影”或“核”;近边缘的部分比较淡一点,叫做“半影”(图1)。本影和半影都可能单独存在。在一个大黑子群里面常常会发现在一片半影中有几个大小不同的本影。大的黑子群,在日出或日落的时候,用肉眼也能够看见。黑子在我国历史上就有不少的记载。“汉书”中的“五行志”里说:“汉成帝河平元年(公元前28年)三月乙未,日出黄,有黑气,大如钱,居日中央。“这段话 Black spots often appear on the bright sun. This kind of spot is called “black sun”. Sunspots sometimes exist alone, sometimes in pairs, and sometimes in groups. The central part of the big sunspot is always darker, called “Umbra” or “nuclear”; the near edge is a bit lighter, called “penumbra” (Figure 1). Umbra and penumbra may exist separately. In a large sunspot group, it is often found that there are several different umbras in a penumbra. Large sunspots can be seen with the naked eye at sunrise or sunset. Sunspot has many records in the history of our country. The “Five Elements” in the “Han Book” states: “In the first year of Hanping Emperor Heping (28 BC), March B was not a sunrise. It was yellowish and black, and it was as big as money.