Planet X has a long and storied history of non-existence. For about 130 years, astronomers have been discussing the existence of an additional planet as planets to explain discrepancies in the orbits of known planets (especially Neptune and Uranus). Later, the list of differences was expanded to cover trans-Neptunian objects. But none of the Planet X candidates discovered, including Pluto, have the mass as a location to explain observations.
Primordial black holes are now proposed as the last planet X (as planet 9, since Pluto was destroyed).
Orbital weirdness
The origin of Planet X begins with the discovery of Neptune. Neptune was not found by accident: observations of scents in the orbit of Uranus were used to calculate the location of Neptune, and it was later found.
This is a game that can be played more than once. Astronomers then saw that the orbits of Uranus and Neptune could be better explained by the existence of another large planet. Subsequent observations have found several objects: Pluto and Charon, Sedna, and Eris to name a few. Not one of these distant bodies is large enough to be Planet X. But some of their orbits may also suggest that a new planet is needed.
Some trans-Neptunian objects have very rare orbits. Many are clustered and have very elliptical orbits, and there is a subgroup that performs well from the plane in which the planets orbit. This is unusual because the action of gravity and the nature of the disk that form the planets typically keep everything close to the same orbital plane. Locations with a lot of inclination would suggest that something is pulling the objects out of the plane.
A planet large and far enough from the sun could explain these orbits. Indeed, researchers have calculated a range of different planetary masses and orbits that may take into account the behavior of objects such as Sedna.
Coincidentally, the required masses and distances correspond to an observed gravitational lens anomaly – an excess of events in which the gravitational influence of an invisible object distorts the light of distant stars. That is, there is mass out, and it is invisible. Could this be a new planet?
A series of unlikely events
That, there seems to be mass, but where did it come from? The planet would have to be like 300-1,000AU of the Sun (for reference, Neptune’s orbit is just 30AU), where there is very little rock or gas. Simply put, a planet could not form out of it. One possibility is that the planet formed closer to the Sun and pinged out there through interactions with one or more of the gas giants. However, to stabilize at a distance base, a passing star (or something like that) is required, which seems impossible. The remaining option is that our Sun conquered a fairly wandering planet.
But swalkers need to be driven away from their own solar system, which means most of them move to an honest cliff. As a result, the chances of conquering such a planet in the required orbit are small, though not impossible.
The new paper argues that, if we are looking at an event with low chance, why not a primordial black hole? Primordial black holes may have formed shortly after the Big Bang. And, unlike black holes formed from collapsed stars, they could have masses ranging from small (10μg) and upwards. That means there should be a few with the right mass range. How much is a matter of speculation.
Conceived by the idea, the researchers began rolling d20s: they put primary black holes on a random low number and then concluded that capturing a black hole is about as likely as capturing a wandering planet.
In for a cent, in for a pound
If planet X were indeed a black hole, how would we know? The researchers claim that destruction of dark things is the thing to look for.
No one knows if primordial black holes exist. No one knows if dark matter destroys, and if so, there is no certainty that it does so in a way that can be detected – dark matter could destroy itself to create other forms of dark matter, and leave us, yes, in the dark. Thus, a speculative product of the early Universe cannot be discovered immediately unless another speculative process occurs in the right way. In which case it is possible to confirm if a primordial black hole is part of our family of the solar system.
Underlying the speculation is an interesting coincidence: unexplined gravitational lensing events that happen to be the right mass and distance to explain some very odd orbits of trans-Neptunian objects. That coincidence feels like he is calling for one explanation, which is what the researchers are trying to do. That makes her house of cards useful.
Physical Review Letters, 2020, DOI: 10.1103 / PhysRevLett.125.051103 (About DOIs)
