This new image from the NASA/ESA Hubble Space Telescope is one of the best ever views of Terzan 9, one of the most central globular clusters in our Milky Way Galaxy.
This Hubble image shows the globular cluster Terzan 9, a relic of a generation of long-lived stars that formed in the early Galaxy. The color image was made from separate exposures taken in the visible and infrared regions of the spectrum with Hubble’s Advanced Camera for Surveys (ACS) and Wide Field Camera 3 (WFC3). Three filters were used to sample various wavelengths. The color results from assigning different hues to each monochromatic image associated with an individual filter. Image credit: NASA / ESA / Hubble / R. Cohen.
Globular clusters are densely packed systems of very ancient stars, gravitationally bound into a single structure about 100-200 light-years across.
They are among the oldest known objects in the Universe and are relics of the first epochs of galaxy formation.
Globular clusters contain hundreds of thousands or perhaps a million stars. The large mass in the rich stellar center of a cluster pulls the stars inward to form a ball of stars. The word globulus, from which these clusters take their name, is Latin for small sphere.
It is thought that every galaxy has a population of globular clusters. Some, like the Milky Way, have a few hundred, while elliptical galaxies can have several thousand.
“As the new image of Terzan 9 demonstrates, the hearts of globular clusters can be densely packed with stars,” Hubble astronomers said.
“The night sky in this image is strewn with so many stars that it resembles a sea of sequins or a vast treasure chest crammed with gold.”
Terzan 9 is located in the constellation of Sagittarius, about 700 parsecs (2,283 light-years) from the Milky Way’s center.
Also known as GCl 80.1, it belongs to the inner bulge volume and is among the globular clusters closest to the Galactic center.
“The image of Terzan 9 is from a Hubble program investigating globular clusters located towards the heart of the Milky Way,” the researchers said.
“The central region of our home Galaxy contains a tightly packed group of stars known as the Galactic bulge, which is also rich in interstellar dust,” they added.
“This dust has made globular clusters near the Galactic center difficult to study, as it absorbs starlight and can even change the apparent colors of the stars in these clusters.
“Hubble’s sensitivity at both visible and infrared wavelengths has allowed astronomers to measure how the colors of these globular clusters have been changed by interstellar dust, and thereby to establish their ages.”
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