Caltech-Astronomer Mike Brown Comments on Latest Alternative for Planet-Nine-Theory

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Prof. Mike Brown.

Prof. Mike Brown.

Pasadena (USA) – Common odd orbital properties of some Trans-Neptunian Objects (TNOs) have so far been regarded as an indication of the possible existence of another yet unknown large planet in the outer solar system, dubbed „Planet Nine“. In a recent study, two astronomers question this interpretation of the data and present an alternative theory. (GreWi) has asked Professor Mike Brown, the best-known representative and together with his colleague Konstantin Batygin first descriptor of the likely features of „P9“, for his assessment of this alternative theory.

Just a few days ago Prof. Jihad Touma of the American University of Beirut and Antranik Sefilian of the University of Cambridge had published a paper via and in the “Astronomical Journal”, describing an alternative to the model of another planet with 10 times the mass of our Earth in the outer solar system with the idea of a likewise still unconfirmed massive disc or ring of icy bodies beyond the Neptune orbit.

Together with Konstantin Batygin, Mike Brown was one of the first to describe the properties of an hypothetical ninth planet and to simulate it in actual models of the solar system with the observed characteristics of the deviating trans-neptunian objects. Brown and Batygin are pretty much certain that all observable data speak so far for the existence of such a large single planet mass body, which they search since then intensively. (GreWi) asked Mike Brown about his view on the latest theory by Touma und Sefilian:

GreWi: Dear Prof. Brown, how do you judge the latest theory, which marks an alternative to the one of Planet Nine mainly proposed by you?

Mike Brown: „I like this paper. It’s critical that people look for alternative suggestions, and this is the first time someone has proposed something other than Planet Nine that actually explains the phenomena that we are seeing.“

GreWi: But others suggested alternative explanations before?

Mike Brown: „Other people have suggested explanations that actually did not explain anything. This does. That is encouraging.“

GreWi: So in your opinion the theory by Touma and Sefilian could be valid?

Mike Brown: „While I think that their explanation could work, I think it seems completely implausible. They suggest that rather than a single planet with about 10 times the mass of the Earth, if you divide that mass up into a huge ring of bodies and somehow put that ring into a particular elongated orbit and somehow keep that ring in place for 4 billion years you will see the same effects. I agree, it’s just that explaining this with a particularly oriented ring of objects is significantly more complicated than a simple single planet. If the simpler explanation fails, though, it will definitely be time to start taking more complicated ones more seriously. I don’t think we’re at that stage yet.“

GreWi: But as the proposed ring has not been discovered yet, so hasn‘t your planet?

Mike Brown: „True. But interestingly, a ring of objects would be much easier to
find than a singular planet (since there would be many objects to find) – yet there is no evidence that such a thing exists.“

GreWi: So is the ring-theory wrong?

Mike Brown: „I want to reemphasize that while I don’t think there is any chance that this is the correct explanation, I really like this paper. It is the first time in 3 years that someone has found ANY potential alternative mechanism. The fact that the mechanism they found seems unlikely to exist in our solar system only highlights to me how difficult it is to find alternatives to the power and simplicity of the Planet Nine solution.“

GreWi: Prof. Brown, many thanks for your answers and good luck and success with your search for Planet Nine!