Question

A new planet is discovered. Planet X is observed to orbit the sun every 300 years. What is the semi-major axis of Planet X's orbit in AU?

Answer 1

Data yet to be confirmed: Orbit period is about 15000 years, Perihelion = 200 AU and aphelion 600 - 1200 AU. For these tentative (imprecise )data, semi-major axis is half-sum = 400 to 700 AU.

Explanation:

Refer Science Magazine articles by discoverers. The orbit period might be much higher than Neptune's 165 years for this far-beyond Neptune planet.