哈勃太空望远镜观测到一个闪烁的星团

The densely packed globular cluster NGC 6325 glistens in this image from the NASA/ESA Hubble Space Telescope. This concentrated group of stars lies around 26,000 light-years from Earth in the constellation Ophiuchus.

Globular clusters like NGC 6325 are tightly bound collections of stars with anywhere from tens of thousands to millions of members. They can be found in all types of galaxies and act as natural laboratories for astronomers studying star formation. This is because the constituent stars of globular clusters tend to form at roughly the same time and with similar initial composition, meaning astronomers can use them to fine-tune their theories of how stars evolve.

Astronomers inspected this particular cluster not to understand star formation, but to search for a hidden monster. Though it might look peaceful, astronomers suspect this cluster could contain an intermediate-mass black hole that is subtly affecting the motion of surrounding stars. Previous research found that the distribution of stars in some highly concentrated globular clusters – those with stars packed relatively tightly together – was slightly different from what astronomers expected.

This discrepancy suggests that at least some of these densely packed globular clusters – including perhaps NGC 6325 – could have a black hole lurking at the center. To explore this hypothesis further, astronomers turned to Hubble’s Wide Field Camera 3 to observe a larger sample of densely populated globular clusters, which included this star-studded image of NGC 6325. Additional data from Hubble’s Advanced Camera for Surveys was also incorporated into this image.

Text credit: European Space Agency (ESA)
Image credit: ESA/Hubble & NASA, E. Noyola, R. Cohen

这张由NASA/ESA哈勃太空望远镜拍摄的照片中，密集的球状星团NGC 6325闪闪发光。这个密集的恒星群位于蛇夫座，距离地球大约26,000光年。

像NGC 6325这样的球状星团是由数万到数百万个成员组成的紧密星系团。它们可以在所有类型的星系中找到，是天文学家研究恒星形成的天然实验室。这是因为球状星团的组成恒星往往在大致相同的时间形成，初始成分相似，这意味着天文学家可以利用它们来微调恒星演化的理论。

天文学家检查这个特殊的星团并不是为了了解恒星的形成，而是为了寻找一个隐藏的怪物。尽管它看起来很平静，但天文学家怀疑这个星团可能包含一个中等质量的黑洞，它正在微妙地影响周围恒星的运动。先前的研究发现，一些高度集中的球状星团中，恒星的分布（那些恒星相对紧密地聚集在一起的星团）与天文学家的预期略有不同。

这种差异表明，这些密集的球状星团中，至少有一些（可能包括NGC 6325）可能在中心潜伏着一个黑洞。为了进一步探索这一假设，天文学家利用哈勃望远镜的广角相机3号观测了一个更大的密集球状星团样本，其中包括这张星光熠熠的NGC 6325图像。来自哈勃高级巡天相机的额外数据也被纳入了这张照片中。

文稿来源：European Space Agency (ESA)
影像来源：ESA/Hubble & NASA, E. Noyola, R. Cohen