<b>A Glittering Globular Cluster</b>
<p>A Glittering Globular Cluster
</p><p>This star-studded image from the NASA/ESA Hubble Space Telescope depicts NGC 6717, which lies more than 20 000 light-years from Earth in the constellation Sagittarius. NGC 6717 is a globular cluster, a roughly spherical collection of stars tightly bound together by gravity. Globular clusters contain more stars in their centres than their outer fringes, as this image aptly demonstrates; the sparsely populated edges of NGC 6717 are in stark contrast to the sparkling collection of stars at its centre.
</p><p>The centre of the image also contains some interlopers from closer to home. Bright foreground stars close to Earth are surrounded by criss-cross diffraction spikes formed by starlight interacting with the structures supporting Hubble’s secondary mirror.
</p><p>The area of the night sky which contains the constellation Sagittarius also contains the centre of the Milky Way, which is filled with light-absorbing gas and dust. This absorption of light — which astronomers refer to as extinction — makes studying globular clusters near the Galactic centre a challenging endeavour. 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.
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Credit:
</p><p>ESA/Hubble and NASA, A. Sara
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<pre>Coordinates
Position (RA):  	18 55 5.84
Position (Dec): 	-22° 42' 4.33"
Field of view:  	2.52 x 1.93 arcminutes
Orientation:    	North is 36.7° right of vertical

Colours &amp; filters Band	Wavelength	Telescope
Ultraviolet UV  	275 nm	Hubble Space Telescope WFC3
Optical U       	336 nm	Hubble Space Telescope WFC3
Optical B       	438 nm	Hubble Space Telescope WFC3
Optical V       	606 nm	Hubble Space Telescope ACS
Optical I      	814 nm	Hubble Space Telescope ACS
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<p>Credit: 
</p>
ESA/Hubble and NASA, A. Sara
CC BY 4.0
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