I keep finding more articles that deal with the hypothetical "Planet 9."
This one is from PhysOrg. It recapitulates much of what I've said before in terms of how astronomers began to speculate its existence to begin with. These are factors that include the tug and pull on the movement of Kuiper Belt objects. There are, however, a few interesting new tidbits. Well, new and interesting to me, anyway.
One of the astronomers who is a proponent of Planet 9's existence is Mike Brown. He was actually one of the scientists who was instrumental in downgrading Pluto's status as a planet, in fact puckishly once declaring that "killing Pluto was fun." Now here he is buying into the idea that there is yet another planetary body out there. Nothing really wrong with that. It's just an interesting turn of events.
Another point that I failed to think of in my last post is why hasn't this planet been seen by our powerful telescopes? It should be big enough (ten times the size of Earth, about Neptune-size) and therefore bright enough to at least amount to a dot in the black. That's just it, though. First of all, we don't know exactly where to look. The evidence right now amounts to mathematics, the behaviors of other objects at the edge of the solar system. Without knowing where to look, it's hard to find the right bright spot...particularly in a universe that is full of them. Another factor could be that Planet 9 may be in an orbital plane that often brings it past something very bright, like the Milky Way in the background. It would be difficult to pick this spot out without an informed guess.
One last point I was glad to see was that astronomers are still trying to drive home the fact that Planet 9 is not going to kill us. There has long been this speculation, supposedly based on Sumerian myth, that another planet lurks out there and will one day eventually collide with us. Either that or it exerts another sort of occult force upon us...or something. Fun to think about, especially if the paranormal grabs you. But the truth is that if it exists, Planet 9 has been around for billions of years. It occupies an orbit far beyond that of Pluto and really has very little to do with us. It's not going to collide with us or even come towards us.
We don't even need to have that, though. This is just one indication of the many bizarre mysteries still awaiting us in the universe. I seemed to remember speculation about an object called "Santa" from sometime round ten years ago. What happened with that?
Maybe we'll know more about Planet 9 once Cassini data comes through.
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