A Little Perspective on the New "9th Planet" (and the 10th, and the 11th)

By now you've probably heard the announcement that astronomers Konstantin Batygin and Mike Brown think they've tracked down "Planet 9," a long-rumored large world orbiting in the distant wilderness of the solar system. Even if you haven't heard, the news may sound familiar, since a confusingly similar but completely separate report made the rounds just a month ago. (Students of history will recall that Planet X stories also circulated in 2014 and 2006, and have been a staple of the astronomy