much larger galaxy cluster is the redshift-0.0354 Abell 2063. The cluster is thought to be interacting with the nearby galaxy group MKW 3s, based on radial velocity measurements of galaxies and the positioning of the cD galaxy at the center of Abell 2063. The active galaxy at the center of MKW 3s—NGC 5920—appears to be creating a bubble of hot gas from its radio activity. Near the 5th-magnitude star Pi Serpentis lies AWM 4, a cluster containing an excess of metals in the intracluster medium. The central galaxy, NGC 6051, is a radio galaxy that is probably responsible for this enrichment. Similar to AWM 4, the cluster Abell 2052 has central cD radio galaxy, 3C 317. This radio galaxy is believed to have restarted after a period of inactivity less than 200 years ago. The galaxy has over 40,000 known globular clusters, the highest known total of any galaxy as of 2002. Consisting of two quasars with a separation of less than 5 arcseconds, the quasar pair 4C 11.50 is one of the visually closest pairs of quasars in the sky. The two have markedly different redshifts, however, and are thus unrelated. The foreground member of the pair (4C 11.50 A) does not have enough mass to refract light from the background component (4C 11.50 B) enough to produce a lensed image, although it does have a true companion of its own. An even stranger galaxy pair is 3C 321. Unlike the previous pair, the two galaxies making up 3C 321 are interacting with each other and are in the process of merging. Both members appear to be active galaxies; the primary radio galaxy may be responsible for the activity in the secondary by means of the former's jet driving material onto the latter's supermassive black hole. An example of gravitational lensing is found in the radio galaxy 3C 324. First thought to be a single overluminous radio galaxy with a redshift of z = 1.206, it was found in 1987 to actually be two galaxies, with the radio galaxy at the aforementioned redshift being lensed by another galaxy at redshift z = 0.845. The first example of a multiply-imaged radio galaxy discovered, the source appears to be an elliptical galaxy with a dust lane obscuring our view of the visual and ultraviolet emission from the nucleus. In even shorter wavelengths, the BL Lac object PG 1553+113 is a heavy