最後，當然是由於人類終於發現了核能，同時結合量子力學和愛因斯坦的 E = mc^2，科學界才對恆星的能量來源有了定案：恆星之所以能夠持續釋放出這麼巨大的能量，是因為恆星上的原子核結合在一起的過程會釋出非常多的能量 (叫做核聚變反應)，這些能量變成光、熱，形成一種向外的壓力，與恆星本身的重力抵消，所以恆星可以穩定地照耀億萬年之久。
“We today recognize the antiquity of astrology in words disaster, which is Greek for ‘bad star,’ influenza, Italian for (astral) ‘influence’; mazeltov, Hebrew — and, ultimately, Babylonian — for ‘good constellation,’ or the Yiddish word shlamazel, applied to someone plagues by relentless ill-fortune, which again traces to the Babylonian astronomical lexicon. According to Pliny, there were Romans considered sideratio, ‘planet-struck.’ Planets were widely thought to be a direct cause of death. Or consider consider: it means ‘with the planets,’ evidently a prerequisite for serious reflection.”
“Astrology can be tested by the lives of twins. There are many cases in which one twin is killed in childhood, in a riding accident, say, or struck by lightning, while the other lives to a prosperous old age. Each was born in precisely the same place and within minute of the other. Exactly the same planets were rising at their births. If astrology were valid, how could two such twins have such profoundly different fates?”
“… Ptolemy [古希臘天文及占星學家] believed not only that behavior patterns were influenced by the planets and the stars but also that questions of stature, complexion, national character and even congenital physical abnormalities were determined by the stars… But modern astrologers have forgotten about the precession of the equinoxes, which Ptolemy understood. They ignore atmospheric refraction, about which Ptolemy wrote. They pay almost no attention to all the moons and planets, asteroids and comets, quasars and pulsars, exploding galaxies, symbiotic stars, cataclysmic variables and X-ray sources that have been discovered since Ptolemy’s time.”
“Astronomy is a science — the study of the universe as it is. Astrology is a pseudoscience — a claim, in the absence of good evidence, that the other planets affect our everyday lives. In Ptolemy’s time the distinction between astronomy and astrology was not clear. Today it is.”
卡爾．薩根 (Carl Sagan, 1934 – 1996) 是著名的天文學家，同時亦是一位出色的教育家，終生致力向社會推廣科學。儘管大家可能從未聽過他的名字，但其實大部分人都會聽過他所說的名句：「我們都是星塵。」(“We are all star stuff.”) 其實他就是當年一部著名天文科學電影《超時空接觸》(Contact) 原著小說的作者。
卡爾．薩根一生致力於科學普及和教育工作，著有三十多部作品，曾獲頒普立茲獎。其代表作就是第一代《宇宙：個人遊記》(Cosmos: A Personal Voyage) 系列一共十三集電視紀錄片。第二代《宇宙時空之旅》(Cosmos: A Spacetime Odyssey) 於 2014 年播放，由 Neil deGrasse Tyson 主持，他於節目中講述當年卡爾．薩根如何鼓勵他成為科學家，令人感動。
低質量恆星介乎 0.8 至 8 倍太陽質量，即大約有 26 萬至 260 萬個地球那麼重。我們的太陽就是其中一員。這類低質量恆星的壽命大概為 100 億年左右。當它們接近生命終點時，會開不斷膨脹、脈動，把自己的外殼一層又一層的拋向黑暗的太空深處，最後變成白矮星，被豔麗的「行星狀星雲」包裹著而慢慢地死去。
