韋恩食記

Until the early to mid-twentieth century, scientists believed that stars generate energy by shrinking.
直到20世紀中葉以前，科學家們一直都相信恆星是通過收縮產生能量的。
☐ As stars contracted, it was thought, they would get hotter and hotter, giving off light in the process.
科學家們認為，隨著恆星收縮，它們會變得越來越熱，在這個過程中它們會發光。
☐ This could not be the primary way that stars shine, however.
然而，這可能不是恆星發光的主要方式。
☐ If it were, they would scarcely last a million years, rather than the billions of years in age that we know they are.
假如是這樣的話，它們幾乎不可能存在一百萬年，而據我們所知，它們一直存在了幾十億年。
☐ We now know that stars are fueled by nuclear fusion.
我們現在知道恆星是從核聚變中獲得能量的。
Each time fusion takes place, energy is released as a by-product.
每當核聚變發生時，能量就會作為副產品被釋放。
This energy, expelled into space, is what we see as starlight.
這些能量，被噴射到太空中，就成了我們所看到的星光。
The fusion process begins when two hydrogen nuclei smash together to form a particle called the deuteron (a combination of a positive proton and a neutral neutron).
核聚變的過程開始時，兩個氫原子碰撞在一起，形成了一個被稱作氘核（正質子和中性中子的結合）的原子。
Deuterons readily combine with additional protons to form helium.
氘核很容易與其他的質子結合形成氦。
Helium, in turn, can fuse together to form heavier elements, such as carbon.
氦，又會融合在一起形成更重的元素，比如碳。
In a typical star, merger after merger takes place until significant quantities of heavy elements are built up.
在一個典型的恆星中，合併融合的過程會不停地上演，直到形成大量的重元素。

We must distinguish, at this point, between two different stellar types: Population I and Population II, the latter being much older than the former.
就此，我們必須區分兩種不同的恆星類型：星族I和星族II，後者比前者的年齡要更大。
These groups can also be distinguished by their locations.
這些恆星群也可以根據它們所在的位置來區分。
Our galaxy, the Milky Way, is shaped like a flat disk surrounding a central bulge.
我們的星系，銀河系，它的形狀就像一個圍繞著中央凸起的扁平圓盤。
Whereas Population I stars are found mainly in the galactic disk, Population II stars mostly reside in the central bulge of the galaxy and in the halo surrounding this bulge.
星族I的恆星主要位於銀盤之上，而星族II的恆星大部分都位於銀河系中央凸起的部分，以及凸起部分周圍的光暈中。

Population II stars date to the early stages of the universe.
星族II的恆星可以追溯到宇宙的早期階段。
Formed when the cosmos was filled with hydrogen and helium gases, they initially contained virtually no heavy elements.
這些恆星是在宇宙充滿氫氣和氦氣的情況下形成的，它們最初幾乎不含重元素。
They shine until their fusible material is exhausted.
它們發光直到耗盡易熔物質。
When Population II stars die, their material is spread out into space.
當星族II的恆星死亡的時候，它們所含的物質會分散到宇宙中。
Some of this dust is eventually incorporated into newly formed Population I stars.
其中一些塵埃物質最終併入了新形成的星族I的恆星中。
Though Population I stars consist mostly of hydrogen and helium gas, they also contain heavy elements (heavier than helium), which comprise about 1 or 2 percent of their mass.
雖然星族I的恆星的組成物質大部分是氫氣和氦氣，它們也含有重元素（比氦更重），這些重元素約佔其質量的1%或2%。
These heavier materials are fused from the lighter elements that the stars have collected.
這些較重的物質是由恆星所積聚的較輕的元素融合而成的。
Thus, Population I stars contain material that once belonged to stars from previous generations.
因此，星族I的恆星包含了屬於前代恆星的物質。
The Sun is a good example of a Population I star.
太陽就是一個很好的星族I恆星的例子。

What will happen when the Sun dies?
當太陽死亡的時候會發生什麼？
In several billion years, our mother star will burn much brighter.
幾十億年後，我們的母星將燃燒變得更亮。
It will expend more and more of its nuclear fuel, until little is left of its original hydrogen.
它將消耗越來越多的核燃料，直到它原來所含的氫都所剩無幾。
Then, at some point in the far future, all nuclear reactions in the Sun's center will cease.
然後，在遙遠未來的某個時刻，太陽中心所有的核反應都將停止。

Once the Sun passes into its "postnuclear" phase, it will separate effectively into two different regions: an inner zone and an outer zone.
一旦太陽進入“後原子”階段，它將明顯分解成兩個區域：內區和外區。
While no more hydrogen fuel will remain in the inner zone, there will be a small amount left in the outer zone.
儘管內區不會再有氫燃料，外區還會有少量殘留。
Rapidly, changes will begin to take place that will serve to tear the Sun apart.
很快，將發生分解太陽的變化。
The inner zone, its nuclear fires no longer burning, will begin to collapse under the influence of its own weight and will contract into a tiny hot core, dense and dim.
原子火不再燃燒的內區將在自己的重力下坍塌，收縮成高密度、低亮度的微小熱核。
An opposite fate will await the outer region, a loosely held-together ball of gas.
相反的命運在等待著外區，這是一個鬆散聯繫在一起的氣球。
A shock wave caused by the inner zone's contraction will send ripples through the dying star, pushing the stellar exterior's material farther and farther outward.
內區收縮造成的衝擊波在死去的恆星中造成波紋，把恆星的外部材料進一步向外推。
The outer envelope will then grow rapidly, increasing, in a short interval, hundreds of times in size.
外圍將快速增大，在短期內增大數百倍。
As it expands, it will cool down by thousands of degrees.
在擴展的同時，太陽的溫度將下降幾千度。
Eventually, the Sun will become a red giant star, cool and bright.
最終，太陽將變成一個紅巨星，寒冷而明亮。
It will be so large that it will occupy the whole space that used to be the Earth's orbit and so brilliant that it would be able to be seen with the naked eye thousands of light-years away.
它將變得很巨大，並佔據曾經是地球軌道的空間，又如此明亮，在幾千光年以外都能用肉眼看到。
It will exist that way for millions of years, gradually releasing the material of its outer envelope into space.
它將以這樣的方式存在幾百萬年，逐漸把外圍的物質釋放到太空。
Finally, nothing will be left of the gaseous exterior of the Sun; all that will remain will be the hot, white core.
最終，太陽的外圍氣體跑得一絲不剩；剩下的只有白色的熱核。
The Sun will have become a white dwarf star.
這樣，太陽就變成了一個白矮星。
The core will shrink, giving off the last of its energy, and the Sun will finally die.
它的內核也會收縮，釋放出最後的能量，太陽最終死去。