After that it is expected to become a red giant, as the hydrogen that presently comprises it is exhausted and the sun switches to burning helium instead.
之后，据推测太阳会成变成一颗红巨星，因为到那时候现在构成太阳的氢气燃烧殆尽，太阳转而燃烧氦气。
2
Red giants exist for only a short time—perhaps just a billion years compared with the ten billion the same star may already have spent burninghydrogen like our own sun.
红巨星只在短期内存在——可能只有十亿年，相比起来，像太阳这样的恒星将在百亿年中持续燃烧它们的氢。
3
As the star condenses and compacts it heats up even further, burning the last of its hydrogen and causing the star's outer layers to expand outward.