<Tr> <Th> Mass </Th> <Td> 7025600000000000000 ♠ 6 × 10 kg (est .) ≥ 10 M (est .) </Td> </Tr> <Tr> <Th> Apparent magnitude </Th> <Td>> 22.5 (est .) </Td> </Tr> <P> Planet Nine is a hypothetical large planet in the far outer Solar System, the gravitational effects of which would explain the improbable orbital configuration of a group of trans - Neptunian objects (TNOs) that orbit mostly beyond the Kuiper belt . </P> <P> In a 2014 letter to the journal Nature, astronomers Chad Trujillo and Scott S. Sheppard inferred the possible existence of a massive trans - Neptunian planet from similarities in the orbits of the distant trans - Neptunian objects Sedna and 2012 VP 113 . On 20 January 2016, researchers Konstantin Batygin and Michael E. Brown at Caltech explained how a massive outer planet would be the likeliest explanation for the similarities in orbits of six distant objects, and proposed specific orbital parameters . The predicted planet could be a super-Earth, with an estimated mass of 10 Earths (approximately 5,000 times the mass of Pluto), a diameter two to four times that of Earth, and a highly elliptical orbit with an orbital period of approximately 15,000 years . </P>

Which planet has the longest orbit round the sun