Astronomical and Imaging Data

Useful Informations

NGC 6638 is a dense, “metal-rich” globular cluster located in the constellation Sagittarius. As a member of the Milky Way’s galactic bulge, it is a stable, tightly bound collection of stars held together by mutual gravitational attraction. It was discovered by William Herschel in 1784.

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Key Characteristics and Location

• Location: NGC 6638 is situated in the constellation Sagittarius, a half degree east of the star Lambda Sagittarii (Kaus Borealis). It is part of the Milky Way’s galactic bulge, a high-density region of stars at the center of our galaxy.
• Distance and Apparent Magnitude: It is approximately 31,300 light-years (9.6 kiloparsecs) from Earth. It has an apparent visual magnitude of 9.5, which means it’s too faint to be seen with the naked eye but can be observed with binoculars or a small telescope.
• Physical Properties: NGC 6638 has a classification of VI on the Shapley-Sawyer concentration scale, which indicates a moderately concentrated cluster with a noticeable density increase toward the center. Its mass is estimated to be about 1.89 × 10^5 solar masses. The cluster’s angular diameter from Earth is about 2 arc minutes.

Scientific Significance

• NGC 6638 is a subject of scientific study, particularly for its location and metallicity. Researchers have used telescopes like the Hubble Space Telescope to analyze its stellar population, which is crucial for understanding the formation and evolution of globular clusters and the galactic bulge. The dense nature of globular clusters makes it difficult to distinguish individual stars from ground-based telescopes, but orbital telescopes provide clearer images, allowing astronomers to study the types of stars within the cluster, how they evolve, and the role of gravity in these highly condensed systems.