An Etymological Dictionary of Astronomy and Astrophysics
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One of the three → Galactic center clusters supposed to be the densest young → massive star cluster in the Milky Way. It contains the richest collection of → O stars and → WN Wolf-Rayet stars in any cluster in the Galaxy, thus representing the largest collection of the most massive stars in the Galaxy. With its estimated age of 2-3 million years, the Arches cluster is the youngest of the massive clusters in the Galactic center. → Quintuplet cluster; → Central cluster (Figer et al. 2002, ApJ 581, 258; and 1999, ApJ 525, 750).

Arches, from the presence of Galactic center thermal → arched filaments, about 100 → light-years in projection from the Galactic center (Morris & Yusef-Zadeh, 1985, AJ 90, 2511), from M.E. arche, O.Fr. arche "arch of a bridge," from L. arcus, → arc; → cluster.

Same as the → Coathanger and Collinder 399.

Named after the American amateur astronomer D. F. Brocchi who created a map of the cluster in the 1920s for calibrating photometers; → cluster.

A small, irregular → cluster of galaxies with fewer than 100 galaxies in its core. It has no strongly dominant central galaxy and is notable for the high proportion of spirals. It lies some 500 million → light-years away in the constellation → Hercules; also known as Abell 2151.

→ Hercules; → cluster.

A → galaxy cluster of about 12,000 members about 250 million → light-years (→ redshift z = 0.0176) away, covering 4° of sky in the constellation → Perseus. It is dominated by elliptical galaxies. At its center lies the → radio source→ Perseus A. Also known as Abell 426 (→ Abell catalog).

→ Perseus; → cluster.

A → star cluster situated within an arcsecond, or 0.04 pc, from the → Galactic Center, in the vicinity of the → supermassive black hole Sgr A*. The cluster members are about 40 → main sequence → B-type stars with relatively high orbital → eccentricities (0.3 ≤ e&le 0.95). The most famous member of the S cluster is S2 because of its brightness and its fast orbital motion near Sgr A*. Same as Same as the Sgr A* cluster and S stars. See also other → Galactic center clusters (Figer et al. 2002, ApJ 581, 258; and 1999, ApJ 525, 750).

S, because of proximity to → Sgr A*; → cluster.