Hubble Observations Give “Missing” Globular Cluster Time to Shine

Tracy Vogel

July 3, 2025

Bright stars cluster against a black background. The stars are more densely concentrated in the center of the image. The stars appear mostly white, but bright red and blue stars are also visible sprinkled throughout the image.

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Hubble Observations Give “Missing” Globular Cluster Time to Shine

This NASA Hubble Space Telescope image features a dense and dazzling array of blazing stars that form globular cluster ESO 591-12.NASA, ESA, and D. Massari (INAF — Osservatorio di Astrofisica e Scienza dello Spazio); Processing: Gladys Kober (NASA/Catholic University of America)

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A previously unexplored globular cluster glitters with multicolored stars in this NASA Hubble Space Telescope image. Globular clusters like this one, called ESO 591-12 or Palomar 8, are spherical collections of tens of thousands to millions of stars tightly bound together by gravity. Globular clusters generally form early in the galaxies’ histories in regions rich in gas and dust. Since the stars form from the same cloud of gas as it collapses, they typically hover around the same age. Strewn across this image of ESO 591-12 are a number of red and blue stars. The colors indicate their temperatures; red stars are cooler, while the blue stars are hotter.

Hubble captured the data used to create this image of ESO 591-12 as part of a study intended to resolve individual stars of the entire globular cluster system of the Milky Way. Hubble revolutionized the study of globular clusters since earthbound telescopes are unable to distinguish individual stars in the compact clusters. The study is part of the Hubble Missing Globular Clusters Survey, which targets 34 confirmed Milky Way globular clusters that Hubble has yet to observe.

The program aims to provide complete observations of ages and distances for all of the Milky Way’s globular clusters and investigate fundamental properties of still-unexplored clusters in the galactic bulge or halo. The observations will provide key information on the early stages of our galaxy, when globular clusters formed.

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Media Contact:

Claire AndreoliNASA’s Goddard Space Flight Center, Greenbelt, MDclaire.andreoli@nasa.gov