Planet 9, Wherefore Art Thou?

It's also possible that it is some unknown phenomena...we don't know what we don't know...

Entirely valid. I perhaps should have added a note in the blog that not every astronomer is convinced Planet 9 is out there.

Pluto was originally discovered because of irregularities in the orbits of Neptune and Uranus, the same way that Neptune had been located before it.

"American astronomer Percival Lowell first caught hints of Pluto's existence in 1905 from odd deviations he observed in the orbits of Neptune and Uranus, suggesting that another world's gravity was tugging at these two planets from beyond. Lowell predicted the mystery planet's location in 1915, but died without finding it. Pluto was finally discovered in 1930 by Clyde Tombaugh at the Lowell Observatory, based on predictions by Lowell and other astronomers."

https://www.space.com/43-pluto-the-ninth-planet-that-was-a-dwarf.html

Ironically, having been discovered in this way, Pluto was far too small to deviate the orbits of planets the size of Uranus and Neptune, leading to the conclusion that there is still more out there. Maybe more the work of Planet 9?

From the article: It only exists in mathematical models and computer simulations, likely in the direction of the constellations Cetus or Orion.

This is pretty odd, actually. Orion and Cetus are not in the same part of the sky. Cetus is a large (wide) constellation, and the approximate 'center' is about 60 degrees from the 'center' of Orion. It's a bit like saying something is in the direction of Washington, DC or Boston, MA, while skipping over Baltimore, Philadelphia, and New York City.

Also, neither constellation contains the Ecliptic, the path in the sky along which most of the other planets are found. (Though the ecliptic passes near a corner of Cetus.)

All in all, this seems like a rather unimpressive guess for the possible planet's location.

Also, neither constellation contains the Ecliptic, the path in the sky along which most of the other planets are found.

Planet 9 is not supposed to be found in the ecliptic plane. Its orbit is thought to be about 30 degrees from the ecliptic plane.

As Planet 9 couples gravitationally to the Trans Neptunian Objects (TNOs) there is a transfer of angular momentum, causing a precession of the TNOs' orbits, much like the earth precesses due to tidal interaction.

https://en.wikipedia.org/wiki/Planet_Nine

One of the indications for the existence of Planet 9 that I've seen quoted is that the sun rotates in a plane that is 6 degrees from the ecliptic plane.

"Planet Nine—the undiscovered planet at the edge of the Solar System that was predicted by the work of Caltech's Konstantin Batygin and Mike Brown in January 2016—appears to be responsible for the unusual tilt of the sun, according to a new study.

The large and distant planet may be adding a wobble to the solar system, giving the appearance that the sun is tilted slightly.

"Because Planet Nine is so massive and has an orbit tilted compared to the other planets, the solar system has no choice but to slowly twist out of alignment," says Elizabeth Bailey, a graduate student at Caltech and lead author of a study announcing the discovery.

All of the planets orbit in a flat plane with respect to the sun, roughly within a couple degrees of each other. That plane, however, rotates at a six-degree tilt with respect to the sun—giving the appearance that the sun itself is cocked off at an angle. Until now, no one had found a compelling explanation to produce such an effect. "It's such a deep-rooted mystery and so difficult to explain that people just don't talk about it," says Brown, the Richard and Barbara Rosenberg Professor of Planetary Astronomy.

https://phys.org/news/2016-10-curious-tilt-sun-undiscovered-planet.html

Thanks.

This explains why they're not looking along the ecliptic per se, but it doesn't explain why they're looking at two regions so far apart.

And if they are looking at a region (or regions) 30 degrees from the ecliptic plane, it seems odd to be looking in Cetus which, as I mentioned, is close to the ecliptic plane.

"...why they're looking at two regions so far apart."

It's my "WA guess" that when they run the simulation, plugging in multiple locations for Planet 9, there are two positions that match the data with the highest probability. Just a guess, though.

And if they are looking at a region (or regions) 30 degrees from the ecliptic plane, it seems odd to be looking in Cetus which, as I mentioned, is close to the ecliptic plane.

The orbit of Planet 9 would lie in a plane passing through the sun. This plane would have to intersect the ecliptic plane (which also passes through the sun) in a line extending in two directions. These directions would be almost diametrically opposite from our viewpoint, given that earth's orbit is much closer to the sun than that of Planet 9.

Ok, so 'up to 30 degrees from the ecliptic plane'. That would make sense.

Maybe it (Planet 9) hasn't been found yet because it is not a single planet but rather a disjunct swarm of dwarf planets from which Pluto is an escapee?

You stole my thunder dude, but good on you. My only addition is it (they) could be a number of swarms, I like the term flocks better, that given the ridiculously large transit circumference could co-exist on the same or near same orbital path.

Neptune has an orbital period of 165 years. Pluto has an orbital period of 248 years but was only discovered 88 years ago. This makes me wonder if these orbital perturbations implying a ninth planet farther out than Pluto may just be orbital measurement uncertainties. On the other hand, wow that must be some incredibly accurate motion measurements of things very far away.

Big thumbs up to this. Full of info that most people have never heard.

I have to agree with you, Planet 9 is a bad term. I always thought old Pluto got a bad rap. Using the term Planet X would isolate the totally unrelated matter of whether Pluto is a planet from the topic of this discussion, whether there is an unknown body influencing the motion of the members of the known solar system.

Some alien civilization might well consider only Jupiter, Saturn, Uranus, and Neptune as being significant enough to qualify as planets. We seem to feel that insignificant rocks like earth are important because we grew up here.

There are several issues here. First, dwarf planets are NOT a type of minor planet. As Dr. David Weintraub notes in his book "Is Pluto A Planet?" the term "minor planet" is a synonym for asteroids and comets, objects not large enough or massive enough to be in hydrostatic equilibrium. Pluto does not belong in this category, as it is rounded by its own gravity and is geologically differentiated. Blurring the distinction between these two very different kinds of objects is simply bad science.

We need to drop the distinction between major vs. minor planets, which creates a false dichotomy. Instead, we should consider Alan Boyle's classification system, in which "planet" is a broad umbrella category under which there are numerous subcategories, including terrestrial, gas giant, ice giant, and dwarf planet.

The IAU definition is just one among several currently in use. It does not merit any form of preferential treatment above all other definitions currently in use. The claim that there are 13+ accepted planets in the solar system is in no way a minority view, as a majority of planetary scientists prefer the equally scientific geophysical definition, according to which dwarf planets are a subclass of planets – the meaning intended by Alan Stern when he first coined the term "dwarf planet" back in 1991.

Recently, some of these planetary scientists issued a formal request in the newsletter of the Planetary Science Institute that this hypothetical planet in the outer solar system be referred to by the traditional term "Planet X," as an acknowledgment that the number of solar system planets remains in dispute. This is how it should be referred to in the media and in circles of astronomy. Various writers and publications are now indicating that some scientists choose to call this hypothetical world "Planet X."

It is extremely doubtful that the solar system actually has 750,000 planets. However, the claim that it cannot have "too many planets" has no scientific basis and is not a "twisting" of any argument, especially the geophysical planet definition. If the solar system has 100 or 1,000 planets, then that is what it has. Kids don't need to memorize a list of names to learn about the solar system. That is an archaic method of teaching that goes back to a time when little was known about the planets other than their names. Instead, kids can be taught the different types of planets and their defining characteristics.

The only reason I cite the IAU definition is to illustrate the inconsistency in the arguments of some who support it. The IAU itself distinguished asteroids and comets (Small Solar System Bodies aka minor planets) from dwarf planets. Therefore, referring to dwarf planets as minor planets goes against their own definition.

Regarding Mike Brown, the only thing I am trying to discredit is his claim that he somehow "killed" Pluto, which is both unprofessional and untrue. He also states that the majority of planetary scientists agree with his position, which is not the case, and has even stated that scientists who support the geophysical definition do not really believe in it but are advocating it to support the New Horizons mission. Is he claiming he can read their minds? Furthermore, he is the one who chose the term "Planet 9," which he put in the title of the initial press release about this potential planet as a means of promoting his own agenda, that he "killed" Pluto and that the solar system has only eight planets. It was a slap in the face to all those who advocate the geophysical definition in place of the IAU one.

Just a bit of pedantry:

"Wherefore" means why, not where.

Definition of wherefore

1 : for what reason or purpose : why 2 : therefore

"You are technically correct (and on CR4 the best kind of correct)."

I thought the answer to the question "Wherefore ?" is between three and five.