Planet 9: A new study questions the hypothesis of its existence

Hypothetical Planet 9 first hit the headlines in 2016 when two researchers at the California Institute of Technology claimed to have found evidence of the existence of a massive object ten times the size of Earth and 20 times farther from the Sun than Neptune . Using computer simulations, Mike Brown and Konstantin Batygin succeeded in determining the possible location of the mysterious celestial body.

To this end, the duo considered the observation of six Trans-Neptunian objects whose orbit appeared to be disrupted by a mysterious force of gravity. It turns out that planet nine is the source of this disturbance. However, a new study now refutes this hypothesis.

Outdated notices?

The text published on the arXiv platform, written by Kevin Napier, a PhD student in physics at the University of Michigan, therefore seems to challenge Brown and Batygin’s analysis. Napier and colleagues argue that selection bias led their colleagues at the California Institute of Technology to suspect the existence of a ninth planet in the solar system.

Planetologist Stephanie JH Deppe, co-author of the new study, recently shared her opinion on Twitter. “All evidence for Planet Nine is gone. It doesn’t exist, ”she said, suggesting that previous revelations about the existence of such a planet are likely out of date.

My (probably) last co-authoring paper from graduate school is out !!

In short, all evidence of Planet Nine is gone. It does not exist.

This is the most comprehensive study that has ever explored the original clustering argument led by @kjnapes. Let’s get started!


– Dr. Stephanie Deppe | she / her (@SpaceSciSteph) February 11, 2021

A theory that is not entirely “dead”

Does this mean this new study is permanently burying the ninth planet hypothesis in the solar system? Not quite, because the researchers emphasize in their publication that their work does not categorically reject the old theory.

The orbits of six of the most distant known minor objects around the Sun. Their similar orientation suggests the existence of a planet well beyond Neptune, “Planet Nine”. Photo credit: Wikipedia / Von Tomruen – Own work, CC BY-SA 4.0

The dynamic effects of the mysterious celestial body “are not yet well defined to falsify its existence with current data”. Suddenly, in another publication on the social network with the blue bird, Stephanie JH Deppe states that the theory of planet 9 is “not dead”. Rather than burying the hypothesis entirely, the new report simply qualifies it.

(I’ll note that the entire Planet Nine theory is not dead, just that part of it)

– Dr. Stephanie Deppe | she / her (@SpaceSciSteph) February 11, 2021

Choice bias

As noted above, astronomers believe that Brown and Batygin’s work is selective. The conclusion of these Caltech researchers is, in fact, based on observations of a small part of the sky at certain times of the year at a certain time of day.

The grouping of trans-Neptunian objects would thus be a consequence of the time and place where the observations were made. In fact, these are only visible when their orbit is closest to the sun. Another problem raised by Kevin Napier and his team is the limited and variable sensitivity of existing telescopes. A technical limitation that should be removed when the Vera C. Rubin Observatory (Chile) starts operating in 2022.

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