Caltech
In the 1820s, French astronomer Alexis Bouvard speculated that Uranus’ irregular orbit was affected by an eighth planet in our solar system, which led to the discovery of Neptune. In 2016, referring to the unusual orbit of asteroids in the orbit of Neptune, two astronomers from the California Institute of Technology predicted that there was another planet lurking in the solar system: Planet Nine.
The theory gained traction, no small feat given the quackery predicted by a ninth planet. However, it also cast a lot of doubt.
Last week, a team of Cornell University researchers, led by Kevin Napier, published a pre-print (yet to be judged by a peer) that they believe discredits the evidence supporting the Planet Nine. “The long story short, any evidence for Planet Nine is gone,” tweeted Stephanie Deppe, a co-author of the newspaper.
First, the theory behind Planet Nine. The hypothesis of a large planet that has not yet been detected revolves around extreme trans-Neptune objects, or ETNOs – mini-planets whose orbits around the sun extend far beyond Neptune. (Really far beyond – more than 750 million miles away.) In 2016, two Caltech researchers, Michael Brown and Konstantin Batygin, published a paper examining the unusual orbits of six ETNOs – the orbits are elliptical rather than circular and angled which causes the sun to approach at almost the same point.
Six ETNOs observed by Caltech researchers Michael Brown and Konstantin Batygin have unusual elliptical orbits (purple) that converge at almost the same point around the sun. Brown and Batygin say that their orbits were distorted by Planet Nine, which lives far beyond Neptune.
Caltech
Brown and Batygin estimate a 0.007% chance that this group of jobs would occur by chance. They assume the ETNOs have come into contact with the attraction of Planet Nine, which distorts their orbits. The astronomers even did a simulation that calculated the dimensions of Planet Nine: a radius of two to four times the size of the Earth, with a mass of five to ten times as large.
The new research, by the Cornell team, does not completely rule it out exist of Planet Nine, but rather argues that it is much less likely than Brown and Batygin think.
An important part of the case is biased data. ETNOs are distant and relatively small, making them difficult to see. Astronomers can only spot it if ETNOs orbit the Sun. To achieve this, telescopes are adapted to see a certain part of the sky at a certain part of the year, at a certain time of the day. The method represents the data example, the Cornell team’s article claims.
The team therefore drew data from three different telescopic surveys and evaluated the motion of 14 ETNOs, none of which were included in Brown and Batygin’s 2016 article, and offset the selection bias using a computer simulation. If you spare an incomprehensible astronomy, their finding was that what was previously considered a ‘group’ of ETNOs is actually just prejudice of selection. “TL; DR: U vind [ETNOs] where you look “, explained one of the researchers sharply in a tweet.
In simpler terms: Planet Nine probably does not have to exist for these ETNOs to have the orbits.
“It is important to note that our work does not explicitly exclude Planet X / Planet 9,” the article reads. “Instead, we have shown that there is no evidence to exclude the null hypothesis, given the current set of ETNOs from well-characterized surveys.”