NGC 6397 (also known as Caldwell 86) is a globular cluster in the constellation Ara that was discovered by French astronomer Nicolas-Louis de Lacaille in 1752. It is located about 7,800 light-years from Earth, making it one of the two nearest globular clusters to Earth (the other one being Messier 4). The cluster contains around 400,000 stars, and can be seen with the naked eye under good observing conditions. NGC 6397 is one of at least 20 globular clusters of the Milky Way Galaxy that have undergone a core collapse, meaning that the core has contracted to a very dense stellar agglomeration.
