日期:2022/09/18   IAE 

“太陽為什麼會發光？”是好奇的孩子提出的問題之一，成年人很難提供令人信服的答案。漢斯·貝特 (Hans Bethe) 獲得 1967 年諾貝爾物理學獎，因為他揭示了太陽如何像一個巨大的核反應堆一樣產生大量的熱量和光來支持地球上的生命。

Bethe 的突破性工作源於英國天文學家 Arthur Eddington 爵士在 1920 年代的假設，即太陽內部的高溫和高壓可以迫使原子核融合併產生更重的原子，並在此過程中釋放出巨大的能量。貝特利用他的系列文章全面介紹了原子的中心成分以及這些原子核相互作用的方式，將這些知識應用於理解恆星。

在 1938 年和 1939 年的兩篇論文中，貝特描述了恆星用來產生能量的兩種核反應，並展示了一種如何在內部條件下占主導地位。對於太陽大小（包括太陽大小）的恆星來說，主要的能量供應是通過將四個氫核擠壓在一起形成一個氦核來產生的。在比我們的太陽重的恆星中發現的更極端的溫度和壓力中，主要的能量供應也將氫轉化為氦，但這涉及更複雜的核反應循環，其中碳充當催化劑。阿爾伯特愛因斯坦最著名的方程 E=mc2 表明質量和能量是可以互換的，解釋了為什麼這些聚變反應會產生熱和光。氦的質量小於氫原子核的總和，質量的差異轉化為大量的能量。

根據貝特的理論，這些反應確保有足夠的能量讓太陽照耀數十億年，這比之前的估計要長得多。貝特的理論也幫助我們想像恆星以一種生命週期的形式存在。恆星誕生，它們通過燃燒燃料成長和發展，但在某些時候這種能源必須燃燒殆盡，最終它們會死亡。

“Why does the Sun shine?” is one of those questions asked by curious children to which adults struggle to provide a convincing answer. Hans Bethe received the 1967 Nobel Prize in Physics for revealing how the Sun behaves like a giant nuclear reactor to produce the vast amount of heat and light that supports life on Earth.

Bethe’s breakthrough work stems from the British astronomer Sir Arthur Eddington’s hypothesis in the 1920s that the intense temperatures and pressures within the Sun can force the nuclei of atoms to fuse and create heavier atoms, releasing a tremendous amount of energy in the process. Drawing upon his series of articles that provided a comprehensive account of the central components of atoms and the manner in which these atomic nuclei interact with each other, Bethe applied this knowledge to understanding the stars.

In two papers in 1938 and 1939 Bethe described the two nuclear reactions that stars use to produce energy, and showed how one predominates over the other depending on the internal conditions. For stars up to and including the size of the Sun, the more dominant energy supply is generated by squeezing four hydrogen nuclei together to form one helium nucleus. In the more extreme temperatures and pressures found in stars that are heavier than our Sun, the dominant energy supply also transforms hydrogen into helium, but this involves a more complex cycle of nuclear reactions in which carbon acts as a catalyst. Albert Einstein‘s most famous equation, E=mc2, showing that mass and energy are interchangeable, explains why these fusion reactions create heat and light. The mass of helium is less than the sum of the hydrogen nuclei, and the difference in mass is converted into large quantities of energy.

According to Bethe’s theories, these reactions ensure there is enough energy to allow the Sun to shine for billions of years, considerably longer than previous estimates had predicted. Bethe’s theories have also helped us to imagine stars existing in a form of life cycle. Stars are born, they grow and develop by burning fuel, but at some point this energy source must burn out, and eventually they die.