The "jealous" Planet Nine may have alienated its siblings for their attention to the sun, writes New Scientist.
If a massive Nine Planet exists in our solar system, that could explain why the planets are not in line with the sun.
Eight major planets still revolve around the Sun in the original plane of their birth. The sun rotates on its own axis, but surprisingly, the rotation is tilted: the axis is at an angle of 6 degrees relative to a line perpendicular to the plane of the planets.
There are several theories to explain this strange bevel, including the temporary tug of a passing star eons ago, or the interaction between the magnetic fields of the Sun and the primordial dusty disk that formed the Solar System. But it is difficult enough to explain why the rotation of the Sun is aligned with the planets.
Two groups of astronomers have just come up with a new explanation: a hypothetical massive planet in the outer solar system could interfere with the orbits of all other planets.
Earlier this year, Michael Brown and Konstantin Batygin of the California Institute of Technology in Pasadena argued that Planet Nine may be responsible for some of the erratic movements of ice worlds in the outer solar system. After incorporating the features of this planet's world into our models, more meaning arises in the "intrigues" of heaven.
The idea can now be extended to the orbits of all planets, says Elizabeth Bailey, also of the California Institute of Technology, who did the work with Brown and Batygin.
“Since we believe that Planet Nine has a significant tilt, if it exists, it means that it will tilt other bodies as well," says Bailey, and only in the required volume. “This is one piece of the puzzle that seems to fit in with the rest. And that actually seems to be in favor of the hypothesis of the existence of the Ninth planet."
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The planet should have a mass of 5 to 20 times that of the Earth and a wildly eccentric orbit, reaching at its furthest point a distance 250 times greater than from the Earth to the Sun. This elongated trajectory leads some to speculate that the exoplanet was once abducted by the sun.
If it happened early enough, then its gravitational pull was enough (since the solar system was just born) to change the orbital plane of the planets from alignment with the sun, Bailey says. Jupiter, Saturn, Uranus, and Neptune will all move in the same way, so Planet Nine cannot move them individually, like in pinball. Instead, the entire solar system will tilt as a whole.
The tilt of Planet Nine, not its mass, is the key factor, says Alessandro Morbidelli of the Observatory on the Cote d'Azur in Nice, France, who independently reached a similar conclusion. If it were about mass, then Jupiter would be the prime suspect.
The important thing is that the disturbing planet is out of plane. Jupiter cannot induce its own tilt angle, he says.
However, the tilt of the sun does not prove that Planet Nine exists. This would require observing it with a telescope.