TNOs with periods greater a few thousand years will be extraordinarily difficult to observe. With a slew of new telescopes coming online in the next few years (JWST, LSST, etc.) with widely varying (but complimentary) abilities we might actually be able to settle this.

ECO, think big! The accumulation of verifiable facts over the next few decades will not settle anything.

Bad News...The True Believers will continue to delude themselves that phenomena such as Planet Nine are deliberately directed at them. That the outlier planetesimal is heaven or hell. Depending upon their consumption of anti-depressant medications.

The Good News is that this accumulation of verifiable data will build the opportunity to figure what questions need to be asked next.

"It might be lingering bashfully on the icy outer edges of our solar system..." It might not be real. Let's see some telescopic images.

And it should be Planet X. Not Planet Nine. That's either Neptune or Pluto, depending on whether you accept a simple geophysical definition in which hydrostatic equilibrium and orbiting the Sun independently (or not orbiting any star) is enough, in which case Ceres would be a planet, or if you add a minimum diameter of 2000 kilometers. This object, if it exists, would be Planet 14 and counting.

Joshua's longest day, in 1448 BCE, was documented and recorded by ancient Chinese, by the ancient Inca before they lost their writing skills, and by two Canadian Ojibway tribes, to our knowledge. Only in the Middle East does this become a religious event, the area which was ground zero for "those who to earth from heaven came", supposedly. The phenomenon is a cosmological one, and is attributed to the close passing of a large planet about four times the size of Earth temporarily affecting the normal motion of the Earth. Documented evidence taken from even more ancient Sumerian clay tablets report that a large planet once passed so close to Mars that most of Mars' surface water and all of its atmosphere was sucked away.

No sunspots were ever reported prior to the early 1600's. Then massive sunspot activity was recorded. Evidence of a planetary collision? Maybe there was a planet X, and we are still witnessing the gravitational effects of its passages?

We mixed Blabatsky's theosophhy with IRAS point IRAS 1732+239 and we got a consistent orbital inclination of 48.44 +/- 0.23 degrees agreeing well with the UofAZ anticipated values of 18 or,48 degrees. The probability of fortuitous correlation is 1 chance in 250. Using the 4300 year old Akkadian seal, we found an excellent fit of the mass of our Jovian planets relative to the Sun. It also gave us the mass of this body to ben141 +/- 35 Earth masses, far different than the 10 - 20 Earth masses based on ?????. The semi major axis is 291.2 AU, close to the range the Marcos brothers anticipate. It is not a stolen planet, but rather one in a very stable orbit that would not be ejected by a passing star over the lifetime of the solar system (490 AU). Bing:
VULCAN REVEALED
A Dangerous New Jovian Sized Body In Our Solar System
We found it in 2002.

Cool. That's pretty good evidence, if you like William of Ockham's Razor. But I'd still like to see them actually find it and take pictures. Since we keep finding all these super earths, maybe it would be good to have one we can take a look at close up and personal.

No sunspots were ever reported prior to the early 1600's. Then massive sunspot activity was recorded. Evidence of a planetary collision? Maybe there was a planet X, and we are still witnessing the gravitational effects of its passages?
"Chinese astronomers recorded solar activity around 800 B.C. and astronomers in both China and Korea frequently observed sunspots. ... "In the third year of Lothar, emperor of the Romans, in the twenty-eighth year
of King Henry of the English...on Saturday, 8 December, there appeared from the morning right up to the evening two black spheres against the sun." This description of sunspots, and the earliest known drawing of sunspots, appears in John of Worcester's Chronicle recorded in 1128." http://chandra.ha...cord.pdf

Chinese astronomers recorded solar activity around 800 B.C.
..doesn't mention sunspots, more likely prominences.
and astronomers in both China and Korea frequently observed sunspots. ...
..reads like author's lead-in to the description of the "spheres".
two black spheres against the sun
..not sunspots, but probably transiting planets Venus and/or Mercury.