In 2014, a bold – and somewhat controversial – study claimed there was a mystery planet lurking in the far reaches of our solar system. Dubbed Planet Nine, it was “spotted” in January 2016 using mathematical modelling and computer simulations and was said to be interfering with the orbits of known objects in the Kuiper Belt.
These calculations were later thrown into doubt following claims of biases in the data. Now, the hypothesis has swung back in favour after Spanish astronomers analysed the orbits of a special type of so-called trans-Neptunian objects known as extreme trans-Neptunian objects, or ETNOs. This analysis, once more, points to a planet-sized object having a direct impact on these orbits.
The astronomers, from the Complutense University of Madrid, used calculations and data mining to study the distances from these objects’ “nodes” to the sun. Nodes are the two points where the orbit of an object body crosses the plane of the solar system. Every planet, comet, and asteroid orbiting around the sun lines up during its respective orbit cycle, making a sort of “flat disk” known as the orbital plane. The nodes are the exact points where the probability of interacting with other objects is most likely, and therefore, at these points the ETNOs may see a drastic change in their orbits, or even a collision. Because the position of these nodes is dependent on the size and shape of the orbit, studying them is free from observation bias, too.
During their analysis, Carlos de la Fuente Marcos and his team discovered that the nodes of 28 know ETNOs are clustered in certain ranges of distances from the sun. What’s more, the astronomers spotted a correlation, where none should exist, between the positions of the nodes and their inclination.
“If there is nothing to perturb them, the nodes of these extreme trans-Neptunian objects should be uniformly distributed, as there is nothing for them to avoid, but if there are one or more perturbers, two situations may arise,” explained De la Fuente Marcos.
One possibility is that the ETNOs are stable, which in this case means you’d expect their nodes to be further away from the path of a possible mystery object as possible, but if they are unstable they would behave as comets that interact with Jupiter do, in which one of their nodes is close to this orbit of the hypothetical celestial body.
“Assuming the ETNOs are dynamically similar to the comets that interact with Jupiter, we interpret these results as signs of the presence of a planet that is actively interacting with them in a range of distances from 300 to 400 AU,” continued De la Fuente Marcos. “We believe that what we are seeing here cannot be attributed to the presence of observational bias”.
The authors claim this study adds further, unbiased, support for the existence of Planet Nine, as suggested by Mike Brown and Konstantin Batygin from Caltech, and in the original study proposed in 2014 by Scott Sheppard from the Carnegie Institute and Chadwick Trujillo from the University of North Arizona. The latest research was published in the journal MNRAS: Letters.
What is Planet Nine?
If Planet Nine exists, studies suggest it has a mass around 10 times that of Earth and orbits 20 times farther from the sun, on average, than Neptune does (which orbits at a distance of 2.8 billion miles). At these distances, it would take Planet Nine between 10,000 and 20,000 years to orbit the sun.
The 2016 data would put Planet Nine at 5,000 times the mass of Pluto, too, meaning there would be no question about the classification of the planet. Unlike the class of smaller objects, known as dwarf planets, Planet Nine “gravitationally dominates” its neighborhood of the solar system.
Image: NASA
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