Not so fast: why there likely isn't a large planet out beyond Pluto (Synopsis)

“Finding out that something you have just discovered is considered all but impossible is one of the joys of science.” -Mike Brown

Earlier today, the team of Pluto-killer Mike Brown and Konstantin Batygin announced that they had found evidence of a ninth planet in our Solar System beyond the orbit of Pluto, larger and more massive than even Earth.

However, a closer inspection of the work shows that they predict a few things that haven't been observed, including a population of Kuiper belt objects with large inclinations and retrograde orbits, long-period Kuiper belt objects with opposite ecliptic latitudes and longitudes, and infrared data showing the emission from such an outer world. There are many good reasons to be skeptical, and not conclude that there's a ninth planet without more (and better) evidence.
Image credit: K. Batygin and M. E. Brown Astronom. J. 151, 22 (2016), with modifications/additions by E. Siegel. Image credit: K. Batygin and M. E. Brown Astronom. J. 151, 22 (2016), with modifications/additions by E. Siegel.

Go read the whole story -- and additional information you won't find anywhere else -- over at Forbes.

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" it’s quite likely that there’s a much more mundane explanation for what we’ve seen so far, and further evidence will point the way."

Bummer, this new planet newz is all over the place.

By Ragtag Media (not verified) on 20 Jan 2016 #permalink

So we're meant to be skeptical about a possible planet, but some strange exotic "dark" matter that's completely undetectable but makes up most of the universe is somehow believable? :)

Yeah, because there's evidence for dark matter but one for a large kuiper belt object is shaky at best.

Just because you're ignorant doesn't mean it's a good state to be in.

There's no _direct_ evidence for dark matter. It's the luminiferous aether of the 21st century.

Yes there is.

And no it isn't.

And WTF wrt aether?

I worried about the observation too, but more from the point of insufficient low likelihood for chance alignments akin to the look elsewhere effect of particle physics. But both naively extrapolating the likelihood for 6 of the 11 found objects (with the 5 perpendiculars), and using a binomial toy model for the orbits that gets the likelihood for the 6 on the correct order of magnitude, gets me the same low likelihood for random observations that "look elsewhere" demands.

Good idea to list outstanding test of predictions ("consequences"). (The paper makes two more, which are more open.)

Of the three missing factors I wouldn't worry about #2 of found perpendiculars or #3 of the exact resonant mechanism since its constraints are found in the simulations. "... the narrowness of the stable region is indicative of the resonance width." [ ]

#1 is what they need to be looking for, but the faintness of objects makes for selection bias. (E.g. we were lucky the 6 in plane scattered objects were all close at the moment!) Another planet *is* the mundane physics so far. (See how the Nice model with planet resonances predicts many similar features of populations.)

The problem with the article is that it joins some others, where the found observations are taken as evidence for something, but suggests something else would be likelier. But the paper already rejected one alternative (clumped KBOs, had too little mass) and as of yet no one has presented another feasible one.

Nitpicks: All our planets are detected (tested) with several detections in emitted light making for orbit modeling, to exclude comets et cetera. The gravity constraints are great for finding candidates, but not for qualifying them as planets.

Also, if there is a testable definition of 'direct' vs 'indirect' I would like to see it. My take: it is an opinion of a writer of what constitutes "good enough" evidence.

ADDED IN POSTING: I see the same question goes towards the dark matter denier, a basic ingredient of standard cosmology observed many times in many ways.

What is "_direct_" evidence? Why wouldn't the easily seen baryon + dark matter peak (the 3d) in the CMB spectra be enough, since you just have to subtract the baryon matter peak (the 2d). How problematic would a subtraction be?

By Torbjörn Larsson (not verified) on 31 Jan 2016 #permalink