The NASA/ESA Hubble Space Telescope has taken a very detailed image of the bulge globular cluster NGC 6638.
This Hubble image shows the bulge metal-rich globular cluster NGC 6638. Image credit: NASA / ESA / Hubble / R. Cohen.
Globular clusters are dense 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.
It is thought that every galaxy has a population of globular clusters. Some, like our the Milky Way, have a few hundred, while elliptical galaxies can have several thousand.
“Hubble revolutionized the study of globular clusters, as it is almost impossible to clearly distinguish the stars in globular clusters with ground-based telescopes,” Hubble astronomers said.
“The blurring caused by Earth’s atmosphere makes it impossible to tell one star from another, but from Hubble’s location in low Earth orbit the atmosphere no longer poses a problem.”
“As a result, Hubble has been used to study what kind of stars globular clusters are made up of, how they evolve, and the role of gravity in these dense systems.”
NGC 6638, otherwise known as C 1827-255 or GCl 95, is located in the constellation of Sagittarius.
This globular cluster was discovered on July 12, 1784 by the German-born British astronomer William Herschel with his 18.7-inch telescope.
It belongs to the Milky Way’s bulge, a very massive and dense region of stars at the heart of our Galaxy.
To capture the data in this image of NGC 6638, the astronomers used Hubble’s Advanced Camera for Surveys (ACS) and Wide Field Camera 3 (WFC3) instruments.
“The NASA/ESA/CSA James Webb Space Telescope will further our understanding of globular clusters by peering into those globular clusters that are currently obscured by dust,” the researchers said.
“Webb will predominantly observe at infrared wavelengths, which are less affected by the gas and dust surrounding newborn stars.”
“This will allow astronomers to inspect star clusters that are freshly formed, providing insights into stellar populations before they have a chance to evolve.”
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