Hubble captures a sparkling cluster

This starry image from the NASA / ESA Hubble Space Telescope shows NGC 6717, which is more than 20,000 light years from Earth in the constellation Sagittarius. NGC 6717 is a globular cluster, a roughly spherical collection of stars closely linked by gravity. Globular clusters contain more stars in their centers than their outer fringes, as this image clearly demonstrates; the sparsely populated edges of NGC 6717 contrast sharply with the sparkling collection of stars at its center.

The center of the image also contains intruders closer to the house. These bright stars in the foreground reside between the Earth and the cluster. They are easily spotted by the intersecting diffraction peaks that form when their light interacts with the structures supporting the Hubble secondary mirror.

The constellation Sagittarius is in the same area of ​​the night sky as the center of the Milky Way, which is filled with gas and dust absorbing light. This absorption of light, which astronomers call “extinction,” makes it difficult to study globular clusters near the galactic center. To determine the properties of NGC 6717, astronomers relied on a combination of the Hubble Wide-Field Camera 3 and the Advanced Survey Camera.

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