Old Faithful

Apparently, there are these two quasars in the northern sky that are actually one quasar, which astronomers call "Old Faithful" (Not very original). Besides the light that comes right at the earth, there is a galaxy cluster off to one side of this object with enough gravity to redirect some of the light passing by from the quasar back at the earth. This cluster is far enough away from the original quasar so that we see the bent light as a second object...so its the same quasar twice in our sky. Not only do we see two of the same object, but because of the distances involved, the "lensed" quasar's light is delayed around 1 year from the light coming straight at us. This allows astronomers to watch whatever happens in the quasar twice; once now, once in a year. As one of the hosts of the podcast said, its like a TIVO for the universe. The whole idea of the distances, sizes, masses and physics involved is just mind boggling cool.

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(From Dubious Quality)