Planet Nine estimated mass of ten Earths, a diameter two to four times that of Earth, and an elongated orbit lasting 10,000 - 20,000 years. Batygin and Brown suggest that Planet Nine could be the core of a primordial giant planet that was ejected from its original orbit by Jupiter during the genesis of the Solar System. Others have proposed that the planet was captured from another star, is a captured rogue planet, or that it formed on a distant orbit and was pulled into an eccentric orbit by a passing star. As of 2018, efforts have failed to directly observe Planet
Minor planet asteroids. A minor planet seen releasing gas may be dually classified as a comet. Objects are called dwarf planets if their self-gravity is sufficient to achieve hydrostatic equilibrium and form an ellipsoidal shape. All other minor planets and comets are called "small Solar System bodies". The IAU stated that the term "minor planet" may still be used, but the term "small Solar System body" will be preferred. However, for purposes of numbering and naming, the traditional distinction between minor planet and comet is still used. Hundreds of thousands of minor planets have been discovered within the Solar System and thousands