What is Planet Nine?

June 15, 2024

Astronomers have been scouring the outer solar system for signs of a hypothetical ninth planet for almost a decade, without success. However, we may finally be on the cusp of finding it, experts say.

About:

Planet Nine is a hypothetical planet in the outer region of our solar system.
The concept was proposed to explain certain anomalies observed in the orbits of distant trans-Neptunian objects (TNOs), particularly those with highly elliptical and clustered orbits.

Characteristics:

Mass: Estimated to be about 5 to 10 times that of Earth.
Orbit: Believed to have a highly elliptical orbit with a semi-major axis of about 400 to 800 AU (astronomical units).
- One AU is the average distance between Earth and the Sun, roughly 93 million miles or 150 million kilometres.
Orbital Period: Could range from 10,000 to 20,000 years.
Distance: At its closest, it might be around 200 AU from the Sun, and at its farthest, about 1,200 AU.
The hunt for the solar system's potential ninth planet may soon be coming to a close. With the opening of the groundbreaking Vera C. Rubin Observatory in 2025, we may either finally find Planet Nine within the next few years — or rule out the idea for good.