In this video segment adapted from NOVA scienceNOW, learn about the debate over the definition of a planet. Historically, there has been no scientific definition for a planet, leaving astronomers with ...
The mysterious, fabled "Planet 9" will have nowhere to hide once a new astronomical experiment is underway, scientists think. Some scientists believe a mysterious, as-yet-unseen planet might be ...
Some results have been hidden because they may be inaccessible to you
Show inaccessible results