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甄枝強 香港天文學會
要說星星的故事，當然不能不提最接近我們的恆星──太陽。附圖是探測器所拍得的太陽影像，太陽表面不規則的黑斑就是「太陽黑子」。其實太陽黑子並不黑，只是太陽面的溫度高達絕對溫度5,800度，而黑子中心的溫度比正常表面低1,500度，於是較冷的黑子相形之下看起來黑暗，如果有方法把黑子從太陽分離出來，它的亮度比滿月還要光。漢朝《淮南子》有「日中有踆烏」的記載（「踆烏」是有3隻腳的鳥），算是最早的黑子觀測記錄。歐洲要等到17世紀初伽利略透過望遠鏡的觀測才確證太陽有黑子，不過，通過望遠鏡觀看太陽會導致永久失明，讀者千萬不可嘗試。我們現在知道太陽黑子有一個11年的循環活動周期，這原來是一位德國藥劑師施瓦布在1843年所發現的。
Spots on the sun
The sun is the nearest and therefore most observed star. The inset SOHO image shows dark spots on the solar surface. These are called sunspots. The solar surface is as hot as 5800 Kelvin (absolute temperature). Sunspots appear dark because they are cooler than the surrounding by as much as 1500 Kelvin. If we can remove a sunspot to the night sky, it would outshine the full moon! The earliest sunspot record is found in The Huainanzi which mentioned a three-legged bird in the sun. It was 1700 years later, when Galelio pointed his telescope at the sun that the West came to know about sunspots. It is interesting to learn that an apothecary, S. H. Schwabe, who discovered the 11-year solar cycle in 1843.Readers are reminded NEVER to look at the sun through a telescope, as doing so will result in unrecoverable damages of the eye.
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