A star-filled sky is magnificently displayed in this week’s image from the Hubble Space Telescope . The image shows a structure called a globular cluster, which is an enormous collection of tens of thousands or even millions of stars that are tightly bound and densely packed together by gravity.
This particular globular cluster is called NGC 6638 and is located in the constellation Sagittarius. The image was taken with two of Hubble’s instruments operating primarily in the visible light wavelength. Studying these puzzling objects before the Hubble launch was difficult because it takes very high resolution imaging with very little interference to see each star as distinct from the others .
Hubble’s Position Makes Stars Viewable
Hubble scientists describe the image as follows:
“Hubble has revolutionized the study of globular clusters, as stars in spherical clusters are nearly impossible to clearly distinguish with ground-based telescopes. The blurring of Earth’s atmosphere makes it impossible to distinguish one star from another, but from Hubble’s low-Earth-orbit position, the atmosphere is no longer a problem. it doesn’t.”
Globular clusters will soon be studied by another instrument, as such a cluster, named Messier 92 , is the target of an early science program using the James Webb Space Telescope. The project will study star-forming regions using Webb’s NIRCam and NIRISS instruments, which look at the infrared range as opposed to Hubble’s predominantly visible light observations.