简单的回答是，因为系外行星是根据它们围绕的恒星命名的，小写字母表示被发现的顺序。
The simple answer is that exoplanets are named after the stars they orbit, with lowercase letters tacked on in the order the planets are discovered.
天文学家将这颗行星环绕运行的恒星命名为HIP13044，它距离地球2,000光年，目前已经接近生命的尾声。
The star, called HIP 13044, is nearing the end of its life and is 2000 light years from Earth.
例如，在2007年，HARPS发现了另一个命名为葛利斯581的超级地球，它可能处于宿主恒星的宜居区。
In 2007, for instance, HARPS discovered another super-Earth, called Gliese 581d, that may lie within the habitable zone of its star.
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