Question Is there a 9th planet? If so, then how big, dense, and massive is it? What is its orbit around the sun and gravitational effect on the Solar System?

[COLGeek]

There's no chance to be a black hole. If it was, earth and rest of the whole system could be somewhere in the deep space. There is a theory that says, even if a small black hole pass nearby the solar system, all the planets will move pretty far from its current position and it'll be catastrophic. So, I guess there's no black hole. Actually, I think astronomers hide the truth about this 9th planet.

Why hide the truth? What would be gained by this?

 

[Connor]

When we ask "Is there a 9th planet" it's important to remain focussed on the concept of the question. Technically Pluto is still a "planet" but no longer considered a "full planet", instead defined as a "minor planet". Unfortunately there are far too many of these for the term to mean very much at all, although there is of course a subgroup of minor planets called "dwarf planets" that could be considered worth giving a decent amount of credence to.

Pluto is sometimes described as "the prototype dwarf planet" (https://en.wikipedia.org/wiki/Dwarf_planet) so maybe those who are in the Pluto fan club will take some satisfaction out of that title. As for the major problems to Pluto being a fully fledged planet, it doesn't clear its pathway of other large solid bodies, but then technically it could be claimed that Earth doesn't either. I say that because there are claims of a number of bodies that seem to have a "resonance" with Earth. Having said that, Earth definitely dominates its region of space, which Pluto doesn't do, so that should be considered more important.

This presents me with another hypothesis: multiple minor planets may have been the cause of gravitational fluctuations... I'm working out every possible explanation in my head.

 

[Helio]

This presents me with another hypothesis: multiple minor planets may have been the cause of gravitational fluctuations... I'm working out every possible explanation in my head.

Madigan proposed that the objects might self-organize, thus negating the need for a single large object. [see here.]

 

[Catastrophe]

Connor, see:

Kuiper Belt - NEW - Agreed Terms - April 2022 | Space.com Forums

including, inter alia

'Planet Nine'? Cosmic Objects' Strange Orbits May Have a Different Explanation | Space

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