In a Distant Galaxy, Colliding Exoplanets Are Upending What We Knew About Solar System Formation

By Brandon Specktor Solar systems form in a school of hard knocks. Take ours, for example: Earth had barely cooled 4.5 billion years ago when it got slapped in the face by a renegade Mars-size rock, reducing both bodies to giant balls of lava. Scientists believe this cosmic collision spewed so much debris into the air that …