Planet collisions may have rearranged crowded solar systems
Many worlds discovered by Kepler survived ruthless culling
![Kepler 11](https://i0.wp.com/www.sciencenews.org/wp-content/uploads/2015/02/cc_keplersolarsystem_free.jpg?fit=860%2C460&ssl=1)
TIGHT FIT The star Kepler 11 (illustrated) is home to six planets, five of which would fit inside the orbit of Mercury. Most solar systems might form with planets squished even closer together.
Tim Pyle/NASA