: The figure shows one frame from the middle of a hydrodynamical simulation of a high-speed head-on collision between two 10 Earth-mass planets. The temperature range of the material is represented by four colours grey, orange, yellow and red, where grey is the coolest and red is the hottest. Such collisions eject a large amount of the silicate mantle material leaving a high-iron content, high-density remnant planet similar to the observed characteristics of Kepler-107c. (Credit: Zoe M. Leinhardt and Thomas Denman, University of Bristol)
...and Then There's Physics 