UVic doctoral candidate's questioning of ninth planet prompts global buzz

A University of Victoria PhD candidate is garnering international headlines for work that throws cold water on a hot theory about a ninth planet.

Findings from Cory Shankman’s paper, OSSOS VI. Striking Biases in the Detection of Large Semimajor Axis Trans-Neptunian Objects, were published this week in Nature, Forbes, Science, PBS, and The Globe and Mail. The Nature article was republished in Scientific American.

Shankman isn’t too surprised by all the high-profile coverage, given all the buzz last year that built on the theories of US astronomers Mike Brown and Konstantin Batygin that there appeared to be a huge ninth planet beyond Neptune, one with 10 times the mass of Earth.

"Look at the enormous public interest around whether Pluto is a planet or not," says Shankman. "People are captivated by these subjects. People wear t-shirts proclaiming which Pluto camp they're in. If it turns out that there is an unseen planet in the solar system, we'll see a huge impact in science, pop culture, science fiction and maybe even in the way we view ourselves and our small corner of the universe."

The 2014 study that kicked off the ninth-planet fervor posited that the unusual clustering of distant “trans-Neptunian objects”—TNOs, which Shankman describes as dormant comets—had to mean that there was a very large and previously unknown planet in the outer solar system.

After analyzing more than three years of data collected via the Outer Solar System Origin Survey (OSSOS), Shankman didn’t find evidence of clustering. He and his team argue that it was likely observational bias that led scientists to see clustering where there isn’t any.

OSSOS was active from 2013 through early 2017, using the Canada-France-Hawaii Telescope to look at eight patches of sky throughout each year in search of TNOs and map their paths around the sun. More than 800 TNOs were discovered during the survey.

In previous studies where scientists looked at the orbits of distant TNOs, they found that they appeared to cluster. "If the apparent clustering is reflective of what the solar system is really like, that would be telling,” says Shankman. “Something would have to be there to cause this clustering.”

What scientists believed to be evidence of clustering led to the hypothesis that a massive planet, the so-called Planet 9, is hiding unseen in the outer solar system. Shankman and his team looked for the clustering and "found no evidence of clustering in our independent survey."

So does this rule out any possibility of a ninth planet? Definitely not, says Shankman.

“The solar system is an exciting, weird and often mysterious place,” he says. "It may well turn out that there is another planet out there, but in our survey we find no evidence requiring an extra planet in the outer solar system to explain what we’re seeing."