哈勃望远镜研究了一个神秘的星团

Like Sherlock Holmes’s magnifying glass, the NASA/ESA Hubble Space Telescope can peer into an astronomical mystery in search of clues. The enigma in question concerns the globular cluster Ruprecht 106, pictured here. Unlike most globular clusters, Ruprecht 106 may be what astronomers call a single population globular cluster. While the majority of stars in a globular cluster formed at approximately the same location and time, it turns out that almost all globular clusters contain at least two groups of stars with distinct chemical compositions. The newer stars will have a different chemical make-up that includes elements processed by their older, massive cluster companions. A tiny handful of globular clusters do not possess these multiple populations of stars, and Ruprecht 106 is a member of this enigmatic group.

Hubble captured this star-studded image using one of its most versatile instruments, the Advanced Camera for Surveys (ACS). Much like the stars in globular clusters, Hubble’s instruments also have distinct generations: ACS is a third-generation instrument which replaced the original Faint Object Camera in 2002. Some of Hubble’s other instruments have also gone through three iterations: The Wide Field Camera 3 replaced the Wide Field and Planetary Camera 2 (WFPC2) during the last servicing mission to Hubble. WFPC2 itself replaced the original Wide Field and Planetary Camera, which was installed on Hubble prior to its launch.

Astronauts on the space shuttle serviced Hubble in orbit a total of five times and were able to either upgrade aging equipment or replace instruments with newer, more capable versions. This high-tech tinkering in low Earth orbit has helped keep Hubble at the cutting edge of astronomy for more than three decades.

Text credit: European Space Agency (ESA)
Image credit: ESA/Hubble & NASA, A. Dotter

就像夏洛克·福尔摩斯的放大镜一样，NASA/ESA的哈勃太空望远镜可以窥视天文奥秘，寻找线索。这次所讨论的谜团与球状星团Ruprecht 106有关，如图所示。与大多数球状星团不同，Ruprecht 106可能是天文学家所说的单一种群球状星团。虽然球状星团中的大多数恒星形成于大致相同的位置和时间，但事实证明，几乎所有球状星团都包含至少两组具有不同化学成分的恒星。较新的恒星将具有不同的化学组成，其中包括由其较老的大质量星团伴星处理过的元素。极少数球状星团并不拥有如此多的恒星群，Ruprecht 106就是这个神秘星团的一员。

哈勃望远镜使用其最通用的仪器之一——高级巡天相机（ACS）拍摄到了这张星图。与球状星团中的恒星非常相似，哈勃的仪器也有不同的世代：ACS是第三代仪器，于2002年取代了原来的微弱物体照相机。哈勃的其他一些仪器也经历了三次迭代：在哈勃的最后一次维修任务中，广角相机3号取代了广角行星2号相机（WFPC2）。WFPC2本身取代了发射前安装在哈勃望远镜上的原始广角和行星照相机。

航天飞机上的宇航员在轨道上总共为哈勃维修了五次，并能够对老化的设备进行升级，或者用更新、功能更强的版本替换仪器。这种在低地球轨道上进行的高科技修补，帮助哈勃在30多年来一直处于天文学的前沿。

文字来源：欧洲航天局 (ESA)
图片来源：ESA/Hubble & NASA, A. Dotter