A planet-size object that possibly once visited the solar system may have permanently changed our cosmic neighborhood by warping the orbits of the four outer planets, a new study suggests. The findings may shed light on why these planets' paths have certain peculiar features.
For decades, astronomers have debated how the solar system's planets formed. However, most hypotheses agree on the type of orbit the planets should have: circles that are arranged concentrically around the sun and lie on the same plane. (If you viewed them edge-on, you would see only a line.) However, none of the eight planets, including Earth, have perfectly circular orbits. Plus, the planets' paths don't lie precisely on the same plane.
