A hypothetical mysterious planet believed to be responsible for the strange orbits of the outer solar system has just received one of its biggest blows to date.
According to a thorough analysis of extremely distant objects, led by physicist Kevin Napier of the University of Michigan, it is possible that the planet New does not exist, because there is no evidence of its existence. Rather, what astronomers considered to influence the gravity of a planet is, instead, the selection bias in observations.
The preprint paper has been uploaded to arXiv and awaits peer review.
The New Planet burst onto the scene in 2016, when astronomers Konstantin Batygin and Michael Brown of Caltech published an article in The Astronomical Journal supporting an as yet undiscovered planet on the outside of the solar system. The evidence, they said, was found in other objects far beyond Neptune’s orbit.
These objects are called extreme transneptunian objects (ETNOs). They have huge elliptical orbits, which never cross closer to the Sun than Neptune’s orbit at 30 astronomical units and which move beyond 150 astronomical units.
Batygin and Brown found that these orbits have the same angle at the perihelion, the point of their orbit closest to the Sun. They performed a series of simulations and found that a large planet could group orbits in this way.
According to his calculations, the New Planet should be about five to ten times the mass of Earth, orbiting at a distance of between 400 and 800 astronomical units.
Because this hypothetical planet would be so far away and because the sky is so big, it would not be easy to find. Therefore, his search has been continuous.
Just as it would be difficult to find the planet New, so are the ETNOs. These bodies are smaller than a planet and therefore weaker. When they move away from the Sun, we have almost zero chance of seeing them. And this is where some astronomers believe there is a selection bias.
“Because ETNOs follow very elliptical orbits and their brightness decreases as 1 / r4, they are almost always discovered within a few decades of the perihelion,” the researchers wrote in their article.
“In addition, telescopic surveys observe a limited area of the sky, at specific times of the year, at a limited depth. These effects result in a significant selection bias.”
The difficulty of seeing ETNO means that we have not found many. The initial simulations performed by Batygin and Brown were based on only six ETNOs, which were collected from an assortment of surveys with unpublished selection functions; in other words, the selection biases were not clear.
More recent surveys have been thorough about their selection roles. And while no survey has found enough ETNO to constitute a complete statistical population, the combination of surveys may lead scientists to a stronger conclusion. This is what Napier and his team did.
They took five objects from the Outer Solar System Origins Survey (OSSOS) (previously found no evidence of concentration), five objects from the Dark Energy Survey and four objects found by astronomers Scott Sheppard, Chad Trujillo and David Tholen, who has been leading the search for the New Planet.
Since the three surveys had very different objectives, they therefore had different selection functions. The challenge was to resolve these differences so that the objects could be effectively combined in a large survey. To do this, the team designed a survey simulator.
“In essence,” they wrote in their article, “a survey simulator simulates the detections of a model population of bodies in the solar system using the history, depth, and tracking criteria of a survey. function of selecting a survey for a given population, which allows us to explain the bias and therefore understand the true underlying populations. “
If the ETNO grouping was caused by a physical effect, it should have remained consistent with the largest sample of objects analyzed by Napier’s team. In contrast, their results suggested that the ETNO sample was consistent with a uniform distribution of parent bodies in space.
This is not to say that researchers should be careful to find that there is no new planet. It just means that the existence of the planet cannot be inferred from ETNO data. There is not enough information to confirm or rule it out.
Other lines of evidence also point to its existence. For example, the strangely inclined orbits of external objects in the Kuiper belt of the solar system such as Sedna, although astronomers have also proposed other explanations for these behaviors.
A stronger decision will be possible with a larger population of ETNOs and Kuiper belt objects to analyze, which may mean waiting for objects from a more powerful telescope, such as the Vera Rubin Observatory, which is expected to begin operate some year this year.
Meanwhile, the eager hunt for the fleeing planet is provoking some truly amazing discoveries, including some possible dwarf planets that came out to the outer limits of the solar system and a bunch of giant gas moons.
So whether or not the New Planet exists, the debate itself is amazing for science, leading us to discoveries we might not have found.
The study was published on the pre-printed website arXiv.org.