哈勃太空望远镜拍摄到了云中的一个星团

NASA’s Hubble Space Telescope can resolve individual stars in the densely-packed cores of globular clusters like NGC 2210.
Imagine credit: ESA/Hubble & NASA, A. Sarajedini

This striking Hubble Space Telescope image shows the densely packed globular cluster known as NGC 2210, which is situated in the Large Magellanic Cloud (LMC). The LMC lies about 157,000 light-years from Earth and is a so-called satellite galaxy of the Milky Way, meaning that the two galaxies are gravitationally bound. Globular clusters are very stable, tightly bound clusters of thousands or even millions of stars. Their stability means that they can last a long time, and therefore globular clusters are often studied to investigate potentially very old stellar populations.

In fact, 2017 research using some of the data that were also used to build this image revealed that a sample of LMC globular clusters were incredibly close in age to some of the oldest stellar clusters found in the Milky Way’s halo. They found that NGC 2210 specifically probably clocks in at around 11.6 billion years old. Even though this is only a couple of billion years younger than the universe itself, it made NGC 2210 by far the youngest globular cluster in their sample. All other LMC globular clusters studied in the same work were found to be even older, with four of them over 13 billion years old. This tells astronomers that the oldest globular clusters in the LMC formed contemporaneously with the oldest clusters in the Milky Way, even though the two galaxies formed independently.

As well as being a source of interesting research, this old-but-relatively-young cluster is also extremely beautiful, with its highly concentrated population of stars. The night sky would look very different from the perspective of an inhabitant of a planet orbiting one of the stars in a globular cluster’s center: the sky would appear to be stuffed full of stars, in a stellar environment that is thousands of times more crowded than our own.

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Text credit: European Space Agency

NASA的哈勃太空望远镜可以分辨出像NGC 2210这样的球状星团致密核心中的单个恒星。
影像来源：ESA/Hubble & NASA, A. Sarajedini

这张引人注目的哈勃太空望远镜图像显示了位于大麦哲伦云中的被称为NGC 2210的致密球状星团。LMC距离地球约157,000光年，是银河系的一个卫星星系，这意味着这两个星系在引力上相互束缚。球状星团是由数千甚至数百万颗恒星组成的非常稳定、紧密结合的星团。它们的稳定性意味着它们可以持续很长时间，因此球状星团经常被用来研究潜在的非常古老的恒星群体。

事实上，2017年的研究使用了一些同样用于构建这张图像的数据，结果显示，LMC球状星团的样本与银河系晕中发现的一些最古老的星团在年龄上非常接近。他们发现NGC 2210的年龄可能在116亿年左右。尽管这只比宇宙本身年轻几十亿年，但它使NGC 2210成为迄今为止样本中最年轻的球状星团。在同一项研究中，发现所有其他LMC球状星团的年龄更大，其中4个超过130亿年。这告诉天文学家，LMC中最古老的球状星团与银河系中最古老星团同时形成，尽管这两个星系是独立形成的。

这个古老但相对年轻的星团不仅是有趣研究的来源，而且非常美丽，拥有高度集中的恒星群。从围绕球状星团中心一颗恒星运行的行星上的居民的角度来看，夜空看起来会大不相同：天空中似乎充满了恒星，恒星环境比我们的拥挤数千倍。

除了作为有趣研究的来源，这个古老但相对年轻的星团也非常美丽，拥有高度集中的恒星群。从围绕球状星团中心一颗恒星运行的行星上的居民的角度来看，夜空看起来会大不相同：在比我们自己拥挤数千倍的恒星环境中，天空似乎充满了恒星。

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文字来源：欧洲航天局