Not unlike Lawrence-of-Arabia crossing the broiling Sahara Desert on a camel, an astronomer riding herd on a CCD astrocamera, can see-with the aid of this time-exposure digital photographic technology-the weird optical effects of mirages, too. What an astronomer sees in deep space are mirages caused by a phenomena known as gravitational lensing.
Gravitational lensing is a result of a heavy gravity object, such as a galaxy, bending light waves coming from a more distant object (or objects) located far behind it. This effect can create duplicate, triplicate, or even more "copies" of the distant object or objects.
So, where one distant quasi-stellar object-QSO or quasar for short-exists, gravitational lensing produces two quasars in the observer's eyepiece. Such lensing phenomena was predicted by Einstein's General Theory of Relativity.
According to astronomer Bill Keel of the University of Alabama, "If gravity can be properly viewed as a bending of space produced by mass, then light rays should change their direction upon passing a massive object. In extreme cases, we might expect to see multiple images of the same object, formed by light that has gone around opposite sides of the intervening mass."
Keel notes that the world's first example of gravitational lensing involved the odd double quasar known as QSO 0957+561 located in the constellation Ursa Major.
At the time of its discovery in 1979, 0957+561 was a major deep-space find-two identical quasars just a few arcseconds apart appeared in the telescope eyepiece. Indeed, while finding such a literal "twin quasar" would have been a sweet scientific discovery (sadly, none have been found to date), it turned out that the 0957+561 duo was, in fact, the same quasi-stellar object-optically "Xeroxed", so to speak.
I guess you could say finding "Xeroxed" quasars may be stranger than finding a real-life twin quasar. At the very least, the discovery verified Einstein's prediction about gravity affecting space.