This is a globular cluster, a sphere of tens of thousands of stars. Most of them are a whitish color, but there are many bright red, yellow, and blue stars mixed in. The stars are more concentrated in the center of the sphere. As you move farther from the center, there are fewer stars.

C73 (NGC 1851)

Caldwell 73 is a densely-packed globular cluster of stars. Unlike the stars in many known globular clusters, which are about the same age, indicating that the stars formed at roughly the same time, C73 hosts stellar populations with different ages. The cluster is also encircled by a diffuse halo of stars. Although the origins of the halo and multiple star populations are unknown, one idea is that Caldwell 73 is a remnant of two clusters that collided within a dwarf galaxy that once hosted them both.

Credits: NASA, ESA, and G. Piotto (Università degli Studi di Padova); Processing: Gladys Kober (NASA/Catholic University of America)
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Image CreditNASA, ESA, and G. Piotto (Università degli Studi di Padova); Processing: Gladys Kober (NASA/Catholic University of America)
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