Astronomers have recently begun discussing a tantalizing mystery from the far reaches of deep space. NASA scientists have recently announced a number of unusual variances in the orbits of the planets and motion of the Sun, though very small. These observations have led some astronomers to suggest that a previously unknown world could be hidden in the most remote and unexplored areas of our solar system. This could mean that a ninth planet (or 10th, for those who still count Pluto as a planet), is yet to be discovered. While the initial evidence offers only a suggestion of another planet, the idea has energized astronomers to begin a new search for planets beyond Neptune. However, the search for “Planet X,” as it was once called, is hardly new.

The facts on the search for distant worlds in the solar system:

1. American astronomer Percival Lowell popularized the search for this supposed unnamed planet, which he and others referred to as “Planet X,” and Lowell began an in-depth search for it starting in 1906.

2. The discovery of Pluto by American astronomer Clyde Tombaugh in 1930 was initially believed to solve the Planet X mystery, but later observations showed that Pluto was too small to affect the orbits of Uranus and Neptune in any significant way.

3. The Planet X theory was largely discredited as further studies of the orbits of Uranus and Neptune found that the initial problems with the orbits were caused by miscalculations and not another large planet.

4. The Planet X theory lost further ground when NASA announced in 2014 that its probes could not find evidence of any other large planets in our system.

5. Astronomers use careful calculations of orbits using observations, angles, speed, and light to determine the positions of planets and other objects in space.

6. In addition to observations, astronomers use mathematics to project orbits, and among the most elementary mathematical tools being the Laws of Planetary Motion used for centuries.

7. California Institute of Technology (Caltech) astronomers Konstantin Batygin and Mike Brown have published their evidence for another planet, which has led to the renewed search.

8. These scientists have suggested that this planet, if it exists, could have a highly elliptical orbit, different from the more circular orbits of the other planets.

9. If this new planet exists, astronomers believe that it could be 10 times the size of Earth and up to 55 billion miles (90 billion kilometers) from the Sun, giving it an orbit that would take it 10,000 to 20,000 years to complete.

—Dr. Bridges is a professor of history and geography living in Arkansas. He can be contacted at drkenbridges@gmail.com.