Beware, space fans. Planet Nine is under attack and could wink out of existence under the sustained onslaught of … er … some very circumspect Canadians.
Planet Nine, for those who need to be reminded, is a hypothetical celestial body 10 times the mass of Earth that could be lurking at the fringes of our solar system. It became a breaking science story last year after two teams of astronomers proposed its existence to explain an unlikely pattern in the trajectories of several smaller objects that ply the dark depths beyond the known planets.
But now, a team working with data from the Canada-France-Hawaii Telescope has failed to find the telltale pattern that would support the existence of the putative orb. Instead, the Canadian-led study suggests the planet could be nothing more than a statistical fluke that vanishes when the numbers are looked at differently.
"We don't need an extra planet to explain the observations in our survey," said Cory Shankman, a PhD student at the University of Victoria and lead author on the study, which was accepted for publication in the Astronomical Journal on Monday.
The new results are based on the most comprehensive search to date for objects that orbit the sun beyond Neptune, the outermost of the major planets. For the most part, they are smallish lumps of rock and ice about 50 to 100 kilometres across, although a handful – including Pluto – have diameters of more than 1,000 kilometres.
The point of the Canadian-led survey was to understand the distribution and characteristics of these so-called trans-Neptunian objects, not to look for evidence of Planet Nine.
"We started long before these claims came up," said Brett Gladman, an astronomer at the University of British Columbia and a principal investigator on the project. But when the Planet Nine story broke, the team members realized their data might offer an independent test.
Planet Nine's existence was first proposed in 2014 by astronomer Scott Sheppard at the Carnegie Institution in Washington and colleague Chad Trujillo of the Gemini Observatory in Hilo, Hawaii. The pair had discovered a new object with a stretched-out orbit that, taken together with that of another body that was previously known, might suggest the gravitational influence of a third, much more massive and more distant world.
Two years later, Mike Brown and Konstantin Batygin, both at the California Institute of Technology in Pasadena, bolstered the idea by adding four more objects to the list and showing that their orbits were all clustered to one side of the solar system in a way that might be explained by the presence of a large planet that orbited some 200 times farther from the Sun than Earth.
Dr. Brown, who is well known in the media for his 2005 discovery of a large trans-Neptunian object called Eris that triggered Pluto's demotion from planet status, has been a champion of Planet Nine. His contribution to the subject sparked last year's media storm, even though astronomers acknowledged it would be extremely difficult to spot such a dim and distant object with existing technology.
Meanwhile, during a four-year period starting in 2013, the Canadian-led search turned up more than 830 trans-Neptunian objects with well-determined orbits. A key feature of the survey has been the effort to account for observational biases that make it easier to find the objects in some parts of the sky than others. Such biases have the potential to skew impressions about how objects are distributed in the outer solar system, just as drivers might be inclined to conclude that most deer live near highways because the only deer they see are those that are visible from a passing car.
Getting a handle on such biases comes down to "knowing a little bit about what you didn't see by knowing about what you could have seen," Mr. Shankman said.
With these biases carefully accounted for, the team then chose a sample of eight objects from their list to examine for evidence of Planet Nine. The objects were selected because of their similarity to those Dr. Brown and Dr. Batygin had used. But when their orbits were analyzed, they showed no strong signs of clustering.
If Planet Nine had never been proposed, Mr. Shankman said, nothing in the new data would require it.
However, he added, nothing suggests additional planets are not still waiting to be found.
"The solar system is a very exciting, interesting and sometimes weird place," he said. "There may well be another small planet hiding out there somewhere."
When contacted about the result, Dr. Brown gave no indication of throwing in the towel and instead pointed to a recent paper in which he argues that observational bias cannot account for what he and his colleagues have found. In effect, Dr. Brown said, both groups are correct because their surveys are designed differently.
But, he said of the Canadian-led team, "they apparently really hate Planet Nine and will interpret even really supportive data as unsupportive."
David Jewitt, an astronomer at UCLA who opened up the field in 1992 by co-discovering the first small object beyond the orbit of Neptune, said he favoured the way Mr. Shankman's analysis set out the biases inherent in a survey of the region.
"Planet Nine sounds cool and everyone wants it to be here," said Dr. Jewitt, who is not affiliated with either side of the emerging debate, "But that doesn't mean it is."
Mr. Shankman said he did not view his work as an assault on Planet Nine, "but for me personally, I won't be counting my planets before they hatch."