Uranus-Size Planet Hiding at the Edge of Our Solar System Could Be Captured by the Sun

Early models of our Solar System show nine planets, but it was reduced to only eight when Pluto was removed from the list. Using the best models of the history of our Solar System, scientists have recently predicted that the Sun has trapped an extra planet far beyond the orbit of Pluto.

Hidden from Plain Sight

An international team of researchers believes that more interstellar entities could be on this edge of the Solar System than previously thought. The new paper describing their work has yet to be peer-reviewed.

Scientists ran complex computer simulations to assess the tendency of start systems to cast off large planets and their ability to trap an "orphan" planet. A cast-off world needs a kinetic energy threshold to leave the gravitational attraction of its star, and a significant amount of energy is also required for it to be trapped by another start system.

The simulations reveal that a small number of these celestial encounters could lead to a star's gravitational field catching a cast-away orphan planet and claiming it as a member of its system. According to the researchers, this event is more likely to happen when this kind of planet wanders close to the outer edge of the star system's Oort cloud, a hypothetical spherical cloud in the far region of the Solar System where the icy bodies are distributed.

It is estimated that one in every 200-300 stars could host a planet in its Oort cloud. Since there is a likelihood that a star's original planets will be cast out into deep space, scientists conclude that there is a 7% probability that our own Solar System captured an ice giant planet as big as Uranus.

If that is the case, then a celestial body similar to long-sought Planet X, a hypothetical giant planet orbiting the Sun as proposed by Percival Lowell, might be present after all. However, it would be too far away to influence the orbit of Neptune.

However, the scientists explained that this prediction is likely an overestimate since the actual prediction does not consider the instabilities during the early stages of the development of a star system. These factors could affect its star birth cluster or the planet being stripped from passing stars.

What is Oort Cloud?

The Oort cloud is a shell of icy bodies surrounding the Solar System. It was first proposed by Jan Hendrik Oort in 1950 after observing the common properties of comets.

This region begins outside the Kuiper Belt, thought to measure about 20,000 to 100,000 astronomical units or two light years. Such measurement places the Oort cloud in interstellar space, the point beyond the Sun's Heliosphere which defines the boundary between our star system and the region of the Sun's gravitational dominance.

The Oort cloud is believed to be the origin of many long-period comets made of frozen gas and dust. Aside from the comets, the Oort cloud could also contain billions of objects, some so large that they are considered dwarf planets.