Papers present evidence for super Earth in the outer solar system
Two new academic papers, one published in The Astronomical Journal and the other in Physics Reports, present new evidence that a large, as yet undiscovered planet is lurking in the outer solar system.
Both papers coincide with the three-year anniversary of an announcement by astronomers Michael Brown and Konstantin Batygin, both of Caltech, of their theory that a large, distant planet is responsible for the unique clustering of several Kuiper Belt Objects (KBOs) far beyond Neptune and Pluto. Specifically, these KBOs are in orbits perpendicular to the plane of the solar system.
The planet is hypothesized to be in an elliptical orbit around the Sun and its gravitational tug to be the cause of the KBOs’ unique positions. At 37 billion miles (60 billion kilometers) beyond Earth, the body would take approximately 10,000 years to complete one orbit around the Sun.
Some scientists question whether the KBOs are genuinely clustered as Brown and Batygin describe, claiming the apparent clustering could be the result of observation bias rather than real.
Brown and Batygin are not the first to propose the existence of one or more large outer solar system planets. To date, searches have not discovered any of these proposed worlds.
Fred Adams of the University of Michigan, who believes this latest proposed planet exists and is lead author of the second paper, expects it to be found within the next 10 to 15 years through deeper and more sensitive sky surveys.
“I think by 2030, we will have seen it or will have a better idea of where it is,” Adams said. “Of course, it’s also possible that by then, we could have alternative explanations for the observed orbital abnormalities.”
One alternative explanation is that either a star or brown dwarf passed close to the solar system long ago, perturbing the KBOs in question. A citizen science search for the hypothetical planet did turn up several relatively nearby brown dwarfs though none are in solar orbit.
In their latest research, Brown and Batygin created a method to test for bias in each individual observation of the supposedly clustered KBOs. Their method yielded a one in 500 chance that the observations were biased or incorrect.
Adams and his colleagues conducted a separate study using computer models of the solar system’s dynamical evolution and the possible influence of a distant, massive planet. Their findings suggest the proposed planet is smaller and closer to the Sun than initially thought, orbiting approximately 37 billion miles (60 billion kilometers) beyond the Earth.
With a size five to 10 times that of Earth, the planet would be too small to be a gas giant, but would instead be a super-Earth much like those found in many exoplanet systems.
“It is the solar system’s missing link of planet formation,” Adams said. “Over the last decade, surveys of extrasolar planets have revealed that similar-sized planets are very common around other Sun-like stars.”
A super-Earth in the outer solar system, Adams said, would serve as “the closest thing we will find to a window into the properties of a typical planet of our galaxy.”
Laurel Kornfeld is an amateur astronomer and freelance writer from Highland Park, NJ, who enjoys writing about astronomy and planetary science. She studied journalism at Douglass College, Rutgers University, and earned a Graduate Certificate of Science from Swinburne University’s Astronomy Online program. Her writings have been published online in The Atlantic, Astronomy magazine’s guest blog section, the UK Space Conference, the 2009 IAU General Assembly newspaper, The Space Reporter, and newsletters of various astronomy clubs. She is a member of the Cranford, NJ-based Amateur Astronomers, Inc. Especially interested in the outer solar system, Laurel gave a brief presentation at the 2008 Great Planet Debate held at the Johns Hopkins University Applied Physics Lab in Laurel, MD.