Hubble Space Telescope NGC 6717 Globular Cluster Star
Photo credit: ESA/Hubble and NASA, A. Sarajedini
NASA / ESA’s Hubble Space Telescope has imaged NGC 6717, a dazzling globular cluster of stars located over 20,000 light-years from Earth in the constellation Sagittarius. This spherical collection of stars are tightly bound together by gravity, with more in the centers than its outer fringes. When looking at NGC 6717, we see sparsely populated edges instead of the massive collection of stars at its center. Read more for two videos on globular clusters and additional information.

If you look closely at the center of this image, you’ll also see some interlopers from closer to home. More specifically, the bright foreground stars that reside between Earth and the cluster. These can be easily seen by the crisscross diffraction spikes that form when their light interacts with the structures supporting the Hubble Space Telescope’s secondary mirror.

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The constellation Sagittarius is in the same area of the night sky as the center of the Milky Way, which is filled with light-absorbing gas and dust. This absorption of light – which astronomers call “extinction” – makes studying globular clusters near the galactic center challenging. To determine the properties of NGC 6717, astronomers relied on a combination of Hubble’s Wide Field Camera 3 and the Advanced Camera for Surveys,” said NASA.