We have discovered thousands of exoplanets in the last few decades , while the number of satellite in the Solar System has stay at eight – but our discovery of more might not yet be over .

A squad of researchers say they have come up the " substantial statistical evidence yet that satellite 9 is really out there " , after studying a population of distant , mentally ill objects that cross Neptune ’s orbit .

In 2015 , two uranologist from Caltech presented evidence that six objects past the orbit of Neptune were bunch up together in a way that suggested they were being " herded " by something with a large gravitative pull .

Despite hint the major planet could be due to astatistical anomalyand selection bias , the squad believes the objects could be make a motion due to the influence of a heavy target beyond Neptune ’s orbit .

In a recent composition , the squad look at long - menstruation objects that crossed the track of Neptune ’s orbital cavity , finding that their skinny point of domain to the sun was around 15 - 30 astronomic units ( AU ) , with one AU being the aloofness between the sun and the Earth .

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Carrying out pretence to try and discover what best explains the orbits of these objects , the team base that a poser that include a monolithic satellite beyond the realm of Neptune explained the steady state of these objects much better than in computer simulation where planet 9 was not admit .

Though this is intriguing , the analysis does not constrict downwhere to lookfor such a major planet .

It is also not the only possible account for the unusual orbits of trans - Neptunian objects . Another squad believes it could be down to aclose encounter , where a whizz passed by our own Sun several billion years ago in our account .

The team ran 3,000 simulations of scenarios where stars of various masses passed by our own at different space . Though we have only discovered an estimated 1 - 10 percentage of TNOs , making further observation and cogitation of their orbits necessary for a full explanation , the researcher found that a secretive flyby of a somewhat smaller asterisk than our own could bring about a Solar System that looks remarkably similar to how it looks today .

" The well match for today ’s outer Solar System that we observe with our simulations is a star that was slightly lighter than our Sun – about 0.8 solar masses , ” Amith Govind , co - author of the “ close confrontation ” possibility paper , explained in astatement . " This star flew past our Lord’s Day at a space of around 16.5 billion kilometre [ 10.3 billion miles ] . That ’s about 110 times the distance between the Earth and the Sun , a lilliputian less than four times the aloofness of the outermost planet Neptune . ”

gratefully , we might not have too long to wait for either hypothesis to be further tested .

" Excitingly , the dynamics described here , along with all other lines of grounds for Planet 9 , will soon face up a stringent test with the operational commencement of theVera Rubin Observatory , " the generator of the Planet Nine paper conclude . " This forthcoming phase angle of exploration hope to provide decisive insights into the whodunit of our solar arrangement ’s outer compass . "

The “ Planet Nine ” study is published inThe Astrophysical Journal Lettersand the “ confining encounter ” study inNature Astronomy .

An early variant of this article was bring out inApril 2024 .