Mystery giant planet may have sent solar system out of kilter
"Planet Nine", which is believed to exist beyond Pluto, is so big it may have tilted the entire solar system, astronomers believe.
Earlier this year, scientists at the California Institute of Technology (Caltech) announced that a planet 10 times the mass of Earth probably exists around 19?billion miles away.
It was shown to exert such a huge influence that it was called "the most planety of all planets". Now the same team believes Planet Nine is also responsible for one of the biggest mysteries in astronomy - why the solar system lies on a strange tilt.
All the planets, including Earth, orbit in a flat plane with respect to the Sun. But that plane rotates on a six-degree angle with respect to the Sun's equator, a misalignment which has long puzzled astronomers.
"It's such a deep-rooted mystery and so difficult to explain that people just don't talk about it," said Prof Mike Brown, who made the original discovery about Planet Nine.
But now scientists think that the highly tilted orbit of Planet Nine could be responsible. Based on calculations to be presented at the American Astronomical Society's Division for Planetary Sciences annual meeting in California, the huge planet appears to orbit at about 30 degrees off from the other planets' orbital plane which is likely to add a "wobble" to the solar system. Mathematically, given the hypothesised size and distance of Planet Nine, a six-degree tilt fits perfectly into models of the solar system, said Prof Brown.
Elizabeth Bailey, a graduate student at Caltech and lead author of the study added: "Because Planet Nine is so massive and has an orbit tilted compared to the other planets, the solar system has no choice but to slowly twist out of alignment."
Prof Brown and Dr Konstantin Batygin "discovered" Planet Nine, after noticing that 13 objects in the Kuiper Belt - an area beyond Pluto - were all moving together as if being "lassoed" by the gravity of a huge object.
Scientists thought that objects in the belt, a vast region of dwarf planets and icy rocks were only influenced by the gravitational pull of Saturn, Jupiter, Uranus and Neptune. However, they found some objects were clearly being pulled by another body - Planet Nine.
Planet Nine takes between 10,000 and 20,000 years to orbit the Sun and it would take 20 years to send a probe to find out if the planet actually exists. However it could be spotted from Earth using the world's largest telescopes.
Pluto used to be regarded as the ninth planet but was downgraded in 2006 to a dwarf-planet or "plutoid" and is now known unceremoniously as
"asteroid number 134340".