C100 – Caldwell 100

Caldwell 100 (also called Collinder 249) is a loose collection of stars, known as an open cluster, that’s embedded within a large nebula (named IC 2944) about 6,000 light-years away from Earth. The reddish glow of hydrogen gas surrounding the cluster is typical of emission nebulae found in massive star-forming regions. These dense, opaque dust clouds — known as "globules" — are silhouetted against nearby bright stars in IC 2944. They were first found in IC 2944 by astronomer A.D. Thackeray in 1950, and are known as "Thackeray's Globules". Although globules like these have been known since Dutch-American astronomer Bart Bok first drew attention to such objects in 1947, little is still known about their origin and nature, except that they are generally associated with areas of star formation, called "HII regions" because of the presence of hydrogen gas. This Hubble image, taken in visible light in February 1999 using the Wide Field and Planetary Camera 2, shows a small portion of this region. Additional images that helped to establish the true color of the stars in the field were taken in February 2001.