Nine again, fine again, jiggety jig?
Thu 21 Jan 2016 06:54 AM
There's news that there may be a ninth planet after all. It is posited by Mike Brown and Konstantin Batygin to explain the skewed orbits of otherwise inexplicable dwarf planets like Sedna, out beyond the Kuiper Belt. Several such objects have orbits skewed off in the same direction, and modelling suggests that this wouldn't occur without some massive thing skewing them.
Regardless of what you might think about the vexed word "planet", this is exciting. And it underscores that there is scientific value to thinking about the class of things which gravitationally dominate their orbit in a solar system. Whether we use the word "planet" to label that class, it's a natural kind and we need some word for it.
It's also worth mentioning that this might just be a mistaken conjecture. The posited object needs to be spotted with a telescope and observed for a while.