The Twin Quasar is an intriguing object which was discovered in 1979 as a radio source and later identified optically as a pair of seventeenth magnitude quasars about six arc seconds apart. This proved to be the first visible evidence of gravitational mirage an idea first proposed by Einstein in his General Theory of Relativity. The light from the quasar some 5,000 million light years distant is being deflected and concentrated by an intervening foreground galaxy, which is acting as a gravitational lens. To the observers here on Earth we apparently see two images of the single object. The foreground galaxy itself lies almost in line with "B" the more southerly component, and although it has been resolved with professional telescopes, it is unlikely to be seen by amateurs. In this image, the southern component "B" was marginally brighter than "A". (Mag 16.5 and 16.7). This difference can be accounted for by a time delay, a 1.4 year time lag due to differing lengths of the light path around the intervening galaxy. A useful project would be to monitor this object and see how the brightness of each component varies, in 1980 A was brighter than B. Look out also for a possible microlensing event which is a brightening caused by the passage of a star in the lensing galaxy coming directly in line between the quasar and earth. Such a brightening will be in the order of a tenth mag./month over a period of three months and is more likely to occur in component B. Q0957 + 561 A/B can be found about 10 arc minutes north of NGC 3079 in Ursa Major. Refer to Oct 1991 Sky & Telescope for a detailed finder chart. CCD image obtained with 160 sec exposure with Starlite Xpress CCD and 20" f/4 Newtonian. D.Strange Worth Hill Observatory Dorset.
Three years marks the difference between this pair of images of the Twin Quasar. We can see that component "A" is now the brighter.
