Kuiper Cliff
I recently came across a phenomena called the Kuiper cliff. I encountered it in a 2005 'New Scientist' article when searching the topic 'problems in physics'. It's also mentioned on wikipedia. Is there anything to it?

"IF YOU travel out to the far edge of the solar system, into the frigid wastes beyond Pluto, you'll see something strange. Suddenly, after passing through the Kuiper belt, a region of space teeming with icy rocks, there's nothing.

Astronomers call this boundary the Kuiper cliff, because the density of space rocks drops off so steeply. What caused it? The only answer seems to be a 10th planet. We're not talking about Quaoar or Sedna: this is a massive object, as big as Earth or Mars, that has swept the area clean of debris.

The evidence for the existence of "Planet X" is compelling, says Alan Stern, an astronomer at the Southwest Research Institute in Boulder, Colorado. But although calculations show that such a body could account for the Kuiper cliff (Icarus, vol 160, p 32), no one has ever seen this fabled 10th planet.

There's a good reason for that. The Kuiper belt is just too far away for us to get a decent view. We need to get out there and have a look before we can say anything about the region. And that won't be possible for another decade, at least. NASA's New Horizons probe, which will head out to Pluto and the Kuiper belt, is scheduled for launch in January 2006. It won't reach Pluto until 2015, so if you are looking for an explanation of the vast, empty gulf of the Kuiper cliff, watch this space."

http://www.newscientist.com/article/mg18524911.600-13-things-that-do-not-make-sense.html?full=true#.UytBHF4s22w


Craig
u5521291

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I don't recommend New Scientist for anything. Wikipedia is much safer. So it's interesting that Wikipedia mentions this too, although it only cites one individual as thinking that an extra planet is likely.

Funnily enough, Carl's lecture is relevant to this. When the New Scientist article was written, in 2005, they might have counted something rather small as an extra planet. These days we (probably) wouldn't.

Carl says (from email): I'm not sure what the current thinking is about the Kuiper cliff or if its even considered problematic any more. But there are some timely results that pretty much rule out the supposed 'Planet X' explanation: http://news.psu.edu/story/307018/2014/03/07/research/wise-satellite-finds-no-evidence-planet-x-survey-sky

Jason