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Annu. Rev. Astron. Astrophys. 1992. 30:
311-358
Copyright © 1992 by Annual Reviews. All
rights reserved |
The first radio ring, MG 1131+0456, was discovered by
Hewitt et
al. (1988)
(Figure 4) and is formed when a galaxy
lies in front of a
compact radio source and distorts the image of the latter into the form of
an ``Einstein ring.'' Four more radio rings have been discovered,
0218+357
(Patnaik et
al. 1992),
MG 1549+3047
(Lehar et
al. 1992b),
MG 1634+1346
(Langston et
al. 1989),
and 1830-211
(Rao &
Subrahmanyan 1988,
Jauncey et
al. 1991).
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Figure 4. 15 GHz image (upper) and 5 GHz image
(lower) of the radio ring source MG 1131+0456. (Image supplied
courtesy J. Hewitt.)
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