Odds Predict 9th Planet


By Robert Marshall

There could be a ninth planet orbiting our sun in a period that’s suspected to take over 10,000 years to complete. With a mass of 10 Earths, Planet Nine would easily achieve gravitational dominance in its orbital zone, the third and final planetary qualification. While it would fill Pluto’s former position as the ninth planet in our solar system, the unconfirmed body would be significantly farther away. That’s why astronomers have not been able to observe it directly.

Follow the Orbits

Two scientists from the California Institute of Technology — Mike Brown, an observational astronomer, and Konstantin Batygin, a theorist — predicted the existence of Planet Nine. Their investigation began by following the observational discoveries of more than a dozen icy Kuiper Belt objects, all exhibiting similar yet odd orbital patterns. Thinking this was more than coincidence, the Caltech duo approached the pattern as if a missing mass could explain the anomaly. "It's almost like having six hands on a clock all moving at different rates, and when you happen to look up, they're all in exactly the same place," said Brown.

 Mounting Evidence

Simulations show that a would-be ninth planet would give six of the Kuiper objects, and the planet itself, a stable orbital path. All of these objects have highly elliptical orbits, with the planet making its closest approach to one side of the Sun and the Kuiper objects making their closest approach to the opposite side.

A direct observation, even just one pixel in a photograph, could make this a planetary discovery for the history books.

Classroom Discussion

  • Strong scientific theories are based on strong evidence. What are other scientific theories with strong evidence that might be considered controversial?