A Planet is a Planet is a Planet...
Last year, astronomers discovered a "10th planet" in our solar system, orbiting nearly twice the distance from the sun as Pluto. Not much is known about this world, named UB313 until something more catchy can be assigned to it, other than it is larger than Pluto.
Pluto (L) and UB313 (R)
This, of course, forces astronomers to more closely define what is a planet and what is not. UB313 orbits in a zone filled with 1,000 known "trans-Neptunian objects," which might or might not be classified as planets. But if UB313 is larger than Pluto, doesn't it deserve planetary status? Could Pluto, moreover, face a demotion?
Astronomers must now agree on a set of standards for designating bodies as planets rather than asteroids or trans-Neptunian objects. Some have proposed making Pluto the lower threshold for planetary size, therefore preserving its status as a planet. Having moons might also qualify a body as a planet (Pluto has two that we know of).
As we expand our knowledge of space and learn more about what lies in the outer reaches of our solar system, we need to improve how we classify what we find. For we might be in for many more surprises.
Source: Scientific American