Planet smallest known planet is PSR B1257+12A, one of the first extrasolar planets discovered, which was found in 1992 in orbit around a pulsar. Its mass is roughly half that of the planet Mercury. The smallest known planet orbiting a main-sequence star other than the Sun is Kepler-37b, with a mass (and radius) slightly higher than that of the Moon. Every planet began its existence in an entirely fluid state; in early formation, the denser, heavier materials sank to the centre, leaving the lighter materials near the surface. Each therefore has a differentiated interior consisting of a dense planetary core surrounded
Ego the Living Planet the Fantastic Four as they were off planet at the time, fighting Ego. The superpowered quartet attempted to defeat Ego by removing the power cell from one of the attached, propulsion engines, which the Thing attempts to throw into Ego's "brain". In response, an angered Ego attempts to counter with his remaining engines but, with one engine now deactivated, the other propels the now-out-of-control planet into the Sun, its gravitational pull breaking apart Ego's substance. Ego, however, slowly reforms from a few surviving particles and repairs the propulsion unit. Ego then digests a number of Dire Wraiths to replenish its