Today’s post is part of a special series that first appeared on Planet Pailly. Every week, we take a look at a new and interesting scientific term to help us all expand our scientific vocabularies together. Today’s term is:
Planet X is perhaps the most abused term in modern astronomy. The name has been co-opted by astrologers, conspiracy theorists, and on occasion science fiction writers.
The name originated with Percival Lowell, better known as that guy who thought he saw canals on Mars. Based on apparent inconsistencies in the orbits of Uranus and Neptune, Lowell predicted that a ninth planet must exist: something massive enough that its gravity would perturb Uranus and Neptune’s orbits.
With the discovery of Pluto in the 1930’s, Lowell’s Planet X hypothesis seemed to be confirmed.
Later, it became apparent that Pluto was tiny. In fact, it looked like Pluto was barely large enough to be a planet at all.
Then in the late 1980’s and early 1990’s, Voyager 2 revealed that we had miscalculated the mass of Neptune. Uranus and Neptune were exactly where they should have been all along. It was our math that was faulty.
The original Planet X hypothesis is now thoroughly defunct, just like that whole Martian canals thing. However, the term is still used as a placeholder name for any hypothetical as-yet-undiscovered planet hiding in the outer Solar System.
The term also remains annoyingly popular among conspiracy theorists.
P.S.: Planet X discovery announcements seem to pop up every few months. Just a few weeks ago, astronomers announced the possible discovery of a Planet X and a Planet Y. Maybe this time it’s for real, but based on past experiences I’m guessing it’s not. Everyone stay skeptical and don’t get caught up in the hype.
Written by James Pailly.
To read all the articles in the ‘Sciency Words‘ series, visit the Planet Pailly blog.