Hubble telescope captures stunning images of star clusters.
NASA's Hubble Space Telescope has captured a stunning image of Messier 55 (M55), a globular cluster in the constellation Sagittarius that contains around 100,000 stars. The cluster is about 17,000 light-years from Earth and is 100 light-years in diameter. The combined gravity of M55's stars pulls the cluster into a spherical shape, a common trait shared by more than 150 such objects that occupy the Milky Way galaxy. The Hubble Space Telescope can resolve individual stars in the cluster, which is relatively bright but hard to observe from Earth due to its lack of a dense core and faint stars.