银河系最暗的星团（图）  

                               The Milky Way's DimmestStar Cluster

Bright stars may dazzle us, but it's the faint ones that test an astronomer's skill. After all, they're the hardest to detect, making their discovery a greater achievement. Now researchers report that a newfound star cluster in the constellation Pegasus is the dimmest ever seen. Whereas the Milky Way's greatest star clusters radiate millions of times more light than the sun, Segue 3, shown here in an image spanning 64 light-years, ekes out a mere 90 suns' worth of light. As astronomers will report in a future issue of The Astronomical Journal, the dim cluster is ancient, having formed 12 billion years ago. Located 55,000 light-years from Earth and 22,000 light-years below our galaxy's plane, Segue 3 resides in the Milky Way's halo, the population of old stars that surrounds the spiral-sculpted disk housing the sun. The cluster has cast most of its original stars into the halo and is destined to disintegrate completely.

明亮的恒星光彩夺目，然而只有发现暗淡的恒星才能够反映出一个天文学家的技能，毕竟暗淡的恒星是最难以发现的，做出这样的发现才算是获得了较大的成就。目前，研究人员报道说，飞马座一个新发现的星团在所观察到的星团中是最暗淡的。尽管银河系中最大的星团所散发的光亮是太阳的几百万倍，图中所显示的“西格3”星团横跨64光年，勉强发出相当于90个太阳的光亮。正如天文学家们在未来一期《天文学杂志》上即将报道的那样，这个暗淡的星团很古老，形成于120亿年前。西格3星团距离地球55,000光年，位于我们这个星系的平面以下22,000光年。西格3处于银晕中，银晕是包围着螺旋状银盘的一群古老的恒星，而太阳位于银盘中。该星团将绝大多数原始恒星抛至银晕内，并且终将彻底瓦解掉。