Is there an enormous undiscovered planet on the outer reaches of the solar system? The thought has been around since before the invention of Pluto within the Nineteen Thirties. Labeled as planet X, distinguished astronomers had put it forward as an evidence for Uranus’s orbit, which drifts from the trail of orbital motion that physics would expect it to follow. The gravitational pull of an undiscovered planet, several times larger than Earth, was seen as a possible reason for the discrepancy.
That mystery was ultimately explained by a recalculation of Neptune’s mass within the Nineteen Nineties, but then a latest theory of a possible planet nine was recommend in 2016 by astronomers Konstantin Batygin and Mike Brown at Caltech (the California Institute of Technology).
Their theory pertains to the Kuiper Belt, an enormous belt of dwarf planets, asteroids and other matter that lies beyond Neptune (and includes Pluto). Many Kuiper Belt objects—also known as trans-Neptunian objects—have been discovered orbiting the sun, but like Uranus they don’t achieve this in a continuous expected direction. Batygin and Brown argued that something with a big gravitational pull have to be affecting their orbit and proposed Planet Nine as a possible explanation.
This might be comparable to what happens with our own moon. It orbits the sun every 365.25 days, in step with what you’ll expect in view of their distance apart. Nevertheless, the Earth’s gravitational pull is such that the moon also orbits the planet every 27 days. From the standpoint of an out of doors observer, the moon moves in a spiraling motion consequently. Similarly, many objects within the Kuiper Belt show signs of their orbits being affected by greater than just the sun’s gravity.
While astronomers and space scientists were initially skeptical in regards to the Planet Nine theory, there was mounting evidence due to increasingly powerful observations that the orbits of trans-Neptunian objects are indeed erratic. As Brown said in 2024, “I believe it is vitally unlikely that P9 doesn’t exist. There are currently no other explanations for the results that we see, nor for the myriad other P9-induced effects we see on the solar system.”
In 2018, for instance, it was announced that there was a brand new candidate for a dwarf planet orbiting the sun, often known as 2017 OF201. This object measures around 700 kilometers across (Earth is roughly 18 times greater) and has a highly elliptical orbit. This lack of a roughly circular orbit across the sun suggested either an impact early in its lifetime that put it on this path or gravitational influence from Planet Nine.
Problems With the Theory
However, if Planet Nine exists, why hasn’t anyone found it yet? Some astronomers query whether there’s enough orbital data from Kuiper objects to justify any conclusions about its existence, while alternative explanations get recommend for his or her motion, corresponding to the effect of a ring of debris or the more fantastical idea of a small black hole.
The most important issue, nonetheless, is that the outer solar system just hasn’t been observed for long enough. For instance, object 2017 OF201 has an orbital period of about 24,000 years. While an object’s orbital path across the sun might be present in a brief variety of years, any gravitational effects probably need 4 to 5 orbits to note any subtle changes.
Latest discoveries of objects within the Kuiper Belt have also presented challenges for the Planet Nine theory. The newest is often known as 2023 KQ14, an object discovered by the Subaru telescope in Hawaii.
It’s often known as a “sednoid,” meaning it spends most of its time distant from the sun, though throughout the vast area during which the sun has a gravitational pull (this area lies some 5,000AU or astronomical units away, where 1AU is the space from the Earth to the sun). The item’s classification as a sednoid also means the gravitational influence of Neptune has little to no effect on it.
2023 KQ14’s closest approach to the sun is around 71AU away, while its furthest point is about 433AU. By comparison, Neptune is about 30AU away from the sun. This latest object is one other with a really elliptical orbit, however it is stabler than 2017 OF201, which suggests that no large planet, including a hypothetical Planet Nine, is significantly affecting its path. If Planet Nine exists, it might subsequently perhaps must be farther than 500AU away from the Sun.
To make matters worse for the Planet Nine theory, that is the fourth sednoid to be discovered. The other three also exhibit stable orbits, similarly suggesting that any Planet Nine would must be very distant indeed.
Nonetheless, the chance stays there could still be an enormous planet affecting the orbits of bodies throughout the Kuiper Belt. But astronomers’ ability to search out any such planet stays somewhat limited by the restrictions of even unmanned space travel. It might take 118 years for a spacecraft to travel far enough away to search out it, based on estimates from the speed of NASA’s Latest Horizons explorer.
This implies we’ll must proceed to depend on ground- and space-based telescopes to detect anything. Latest asteroids and distant objects are being discovered on a regular basis as our observing capabilities change into more detailed, which should steadily shed more light on what could be on the market. So watch this (very big) space, and let’s see what emerges in the approaching years.