Welcome to another seemingly random edition of The Corner. I say seemingly because there is one unifying thread to all of these musings...me! Welcome back to the Brownian thought processes of yours truly.
Space, the final frontier. And a source for endless debate, even over that which we all thought was gospel truth. To whit, Pluto. A planet? An asteroid? A failed comet? Goofy and Minnie's secret love puppy? For many years now there have been strong arguments for Pluto's demotion from certified planet to friendly asteroid. At a scant 2390 kilometers in diameter Pluto is smaller than our own moon(3,474 kilometers)and has an eccentric orbit that, for part of the Plutonian year, actually brings it closer to us than Neptune, and goes in the opposite direction of the rest of the planets, which seems to indicate that it was a cosmic wanderer that got snared by our greedy Sun. In its favor it is definitely round, and has at least one satellite, Charon. But Marius, you might ask, why are you telling us all this? Good question, and the answer is that this year an object, currently nicknamed Xena, was found beyond the orbit of Pluto that is significantly larger than our 9th planet. Xena, and its companion/satellite Gabrielle, orbit in the outskirts of the Solar system called the Kuiper Belt, which is very distant(extending 5 billion miles past Neptune) and is thought to be the origin of most of the cometary activity in our neck of the galaxy. The discovery of a Kuiper Belt object that is larger than Pluto has revived the planet/not a planet controversy, since Xena's distinction rests firmly upon Pluto's identity. If Pluto is a planet, then shouldn't Xena be considered our 10th planet? And if Xena is not to be considered a planet, why then should Pluto be called one? Ultimately this all boils down to the definition of the word 'planet'. Dictionary.com calls a planet, "A nonluminous celestial body larger than an asteroid or comet, illuminated by light from a star, such as the sun, around which it revolves." But, quite surprisingly, the International Astronomical Union(IAU), whose job it is to define such things, has no clear definition. They admit that until very recently there was no need for a clear definition of what a planet is, but they are working feverishly to come up with one. What is clear is that no matter the IAU decision, this debate won't go away.
Personally I think Luna should be used as the gold standard in this debate. If it's bigger than our Moon, it's a planet. If it's smaller; planetessimal, asteroid, comet, dust, space crap,whatever. And let's not even get started on the satellites of Jupiter, Saturn, and the other gas giants.(but I'll go into those later, 'cause some of them are wayyyy cool)
Ok, gotta run. I'm going to get out my Ouija board and see what Carl Sagan has to say about all this. ;-)