Planet 9?! alternate hypothesis negates (Introduction)

by David Turell , Monday, January 21, 2019, 18:01 (2132 days ago) @ David Turell

Calculations indicate a more massive Kuiper belt would explain the strange orbits that have caused the speculation:

https://www.sciencedaily.com/releases/2019/01/190121103346.htm

"The strange orbits of some objects in the farthest reaches of our solar system, hypothesised by some astronomers to be shaped by an unknown ninth planet, can instead be explained by the combined gravitational force of small objects orbiting the Sun beyond Neptune, say researchers.

"The alternative explanation to the so-called 'Planet Nine' hypothesis, put forward by researchers at the University of Cambridge and the American University of Beirut, proposes a disc made up of small icy bodies with a combined mass as much as ten times that of Earth. When combined with a simplified model of the solar system, the gravitational forces of the hypothesised disc can account for the unusual orbital architecture exhibited by some objects at the outer reaches of the solar system.

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"'If you remove planet nine from the model and instead allow for lots of small objects scattered across a wide area, collective attractions between those objects could just as easily account for the eccentric orbits we see in some TNOs," said Sefilian, who is a Gates Cambridge Scholar and a member of Darwin College.

"Earlier attempts to estimate the total mass of objects beyond Neptune have only added up to around one-tenth the mass of Earth. However, in order for the TNOs to have the observed orbits and for there to be no Planet Nine, the model put forward by Sefilian and Touma requires the combined mass of the Kuiper Belt to be between a few to ten times the mass of Earth.

"'When observing other systems, we often study the disc surrounding the host star to infer the properties of any planets in orbit around it," said Sefilian. "The problem is when you're observing the disc from inside the system, it's almost impossible to see the whole thing at once. While we don't have direct observational evidence for the disc, neither do we have it for Planet Nine, which is why we're investigating other possibilities. Nevertheless, it is interesting to note that observations of Kuiper belt analogues around other stars, as well as planet formation models, reveal massive remnant populations of debris.

"'It's also possible that both things could be true -- there could be a massive disc and a ninth planet. With the discovery of each new TNO, we gather more evidence that might help explain their behaviour.'"

Comment: It is hard to prove a negative. Proof will require seeing Planet Nine