1. 【題目】 All the metals made by a star through nuclear syntheses will be trapped in the core by its own strong gravitational potential. We will never see absorption lines of metals in any stellar spectra. All the metals (A > 4) on the Earth should be made at the moment when the Universe was created and have nothing to do with what stars are doing. 【瓶頸】 查過 Carroll & Ostile 的書，和資料了，還是找不出哪裡不正確... 2. 【題目】 Speaking of a similar phenomenon, a fantastic planetary nebula (PN) appears as a glowing circular ring around its central relic star, i.e. a white dwarf. PNe should be expanding "rings" of hot gas in the space. 【瓶頸】 這是一題反證題，planetary nebula 很明顯不是"ring" ，可是題目有說不能 單純說哪裡不對，要用反證法說如果XX成立，則...，實在沒有頭緒 3. 【題目】 I know those dark lines in the solar (or stellar) spectrum. They are absorption lines caused by molecules above the photosphere, whose emission is characterized by a blackbody radiation at Te = 5777 K. Similarly,emission lines in the solar spectrum must come from molecules ""below"" the photosphere. 【瓶頸】這題也知道不是"below",可是怎麼反證又難倒小弟了... 因為很少寫關係，實在不太會反證法，也許是太習慣只有算式的題目了吧...想想真是 慚愧 不好意思，問題有點多，麻煩各位前輩了，感恩! --

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