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.
Text credit: European Space Agency
影像来源：ESA/Hubble & NASA, A. Sarajedini
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。