Astronomers have come across a curious multi-planetary system orbiting a star that does not seem to have found a memo about where everyone is heading. It generally assumed that planets and their stars tend to rotate in the same direction – after all, they come from the same spinning molecular clouds that allow them to form. However, scientists have described in PNAS a planetary system 897 light-years away where one star revolves opposite its two planets. The paper is available at RXB.
Spinning the planets of the stars is not entirely unheard of, but there a few things that make this system unique. K2-290 is a three-star system consisting of two planets whose main stars orbit K2-290 with the first unusual thing is that the axis of rotation of K2-290A is 124 degrees, which means that it is basically rotating in the opposite direction of its planets. The other is that it orbits both planets in opposite directions, because they are both orbiting in the same plane, which explains this directional difference more strongly.
Incidentally, in our solar system, the sun rotates on an axis roughly 6 degrees, compared to the orbits of the planets, so we are all moving in the same direction. Joshua Win from Princeton University explained in a statement, “This is not the first known phenomenon in the ‘behind’ planetary system – the first was seen more than ten years ago,” Joshua Win from Princeton University explained in a statement. “However, this is a rare case where we think we know what caused the erroneous misconceptions, and the explanations differ from what the researchers thought occurred in other systems.”
It is widely believed that a star and its protoplanetary disk – a dense disk of gas and dust rotating around the star’s planets – where the equatorial part of the star begins to align with the disk plane. When we see a disturbance between the rotation of a star and the orbital motion of its planets, one suggestion to explain is that a kind of violent disturbance occurred while they were forming. However, as both planets orbit in the same plane it is understood that, it is not the star; the disk that affected here, the researchers advised them.
Another hypothesis is that the gravitational pull of a neighboring object can push a planet away, much like a “hot Jupiter” that has the potential significantly change the architecture of the planetary system. Theoretically, this could also be due to a co-star, although two known confused multi-planetary systems where the planets orbit the same planet, a companion has never identified before. However, researchers believe that this is happening here.
They have suggested that the gravitational torque of the distant companion star applied its force to the planetary disk, causing confusion for the K2-290A to tilt the disk. K2-290 has three stars, so it is possible to blame one of the others for this highway. The team suspects that K2-290B is a good candidate for causing confusion, applying sufficient gravitational force to remove the disc.
Researchers believe that this may not only be the first known example of this scenario, it also gives another configuration of the planetary system, meaning we can no longer assume that they and its planetary disk aligned in the first position when we see the faulty systems.