Can planets exist without a star?

The answer

Rogue planets are planetary-mass objects that wander through interstellar space without orbiting any star. They may have been ejected from their original star systems by gravitational interactions with other planets, or they may have formed independently from collapsing gas clouds. A 2011 study estimated that rogue planets in the Milky Way may outnumber stars by a ratio of 2 to 1 - potentially hundreds of billions of dark, wandering worlds. Some could retain subsurface oceans warmed by radioactive decay, theoretically capable of supporting life even without a star's light. In 2020, observations confirmed a growing population of these cosmic nomads.