Context: Astronomers have been searching the outer solar system for nearly a decade for signs of a theoretical ninth planet, with no success so far. However, experts suggest we may be on the verge of a breakthrough in discovering it.

Planet Nine

• About: It is a theoretical celestial body situated in the outer reaches of our solar system.
• Origin: Proposed by Batygin and Brown, Planet Nine might be a remnant core of a giant planet disrupted by Jupiter early in the Solar System's history.

oOther theories suggest it could have been captured from another star, started as a rogue planet, or originally formed on a distant orbit.

• Hypothesis of Gravitational Influence: It is proposed to explain the unusual clustering and alignment of extreme trans-Neptunian objects (ETNOs) in the outer Solar System, suggesting a massive, unseen celestial body shepherding their orbits.
• Characteristics

oMass: Planet Nine is estimated to possess a mass that ranges from 5 to 10 times that of Earth.

oOrbit: The hypothesized orbit of Planet Nine is highly elliptical, with a semi-major axis spanning approximately 400 to 800 astronomical units (AU).

oOrbital Period: It is projected that Planet Nine's orbital period could vary significantly, ranging from 10,000 to 20,000 years.

oDistance: At its nearest approach to the Sun, Planet Nine may be about 200 AU away, while at its farthest, it could extend to around 1,200 AU.

• Existing Planets: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune.
• Future: The search for Planet Nine is set to receive a major boost with the Vera C. Rubin Observatory scheduled to begin operations in 2025. 

oThis observatory's enhanced capabilities may soon provide conclusive evidence either confirming the existence of Planet Nine or debunking the hypothesis altogether.