Only real.

It's the hexagon surrounding Saturn's North Pole.

The Cassini image (above) merely confirms the existence of this surprising structure. It was first observed more than 20 years ago. Like the red spot on Jupiter, it's been there a while. What is it? Best guess:

Multiple images acquired over a 12-day period between Oct. 30 and Nov. 11, 2006, show that the feature is nearly stationary, and likely is an unusually strong pole-encircling planetary wave that extends deep into the atmosphere.

But what kind of wave, exactly? Magnetic? Thermal? Radioactive? Here's an intriguing nighttime image of the pole showing the hexagon and surrounding clouds as they rotate.

Oh, and just to give you the scale: about for Earths would fit inside that hexagon.

Via Slashdot.