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This planet has been seen in a microlensing event. The image of a background quasar (A) is divided into two lobes by the gravity of an invisible foreground galaxy (B). Small fluctuations in only one of these lobes were due to an object within the foreground galaxy moving through the line of sight. The scale and duration of these fluctuations indicated an object of planetary size, about one to a few Earth masses. Nothing is known about the parent star.

Strangest of all the extrasolar worlds is the "quasar planet". This most distant planet has been seen accidentally in a microlensing event. The image of a distant quasar, known as Q0957+561, is divided into two lobes by the gravity of an invisible foreground galaxy, which happens to be in the line of sight. Any fluctuations within the quasar should be visible within both lobes, but an object moving through this gravitational lens within the galaxy will effect only one of these lobes.

Astronomers now have detected a tiny fluctuation within the A lobe, but no corresponding change within the B lobe. This fluctuation was so small that it may have been caused by an Earth-sized planet of roughly the same mass, located within the foreground galaxy and moving exactly through the line of sight.

Unfortunately, this is all we know. There is no information about the planet's orbital parameters, or about the parent star. This planet may even be rogue, wandering through the vast emptiness of space. Given the nature of this discovery method, we will never see it again. This unknown "quasar planet" was our first glimpse into the vast diversity of terran worlds, waiting to be discovered by more sophisticated methods.

Hypothetical view of the "quasar planet"