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Scientists discover backward star, spinning in the opposite direction to its planets

(PhysOrg.com) — All planets move around their stars in the same direction as the star spins—at least that’s what we thought. But now Australian National University astronomer Dr. Daniel Bayliss and his colleagues have found a planet that breaks the mold.
Dr. Bayliss, from the Research School of Astronomy and Astrophysics, is one of 16 early-career scientists unveiling their research to the public at Fresh Science – a national program sponsored by the Australian Government.
Using one of the world’s largest telescopes in Chile, Daniel and his collaborators discovered that a distant planet WASP-17b is moving in the opposite direction to the spin of the star around which it orbits. The discovery throws traditional theories about how planets form around stars into doubt.Hey star! You’re going the wrong way.
Artist’s rendering of the exoplanetary system K2-290, showing the main star K2-290 A, its two planets, and the smaller companion star K2-290 B in the background.

In planetary systems, it’s generally expected planets and their stars rotate in the same direction. Take our own solar system, for example.

Our sun spins in almost the exact same direction as Earth and the rest of the planets orbits, with a small six degree tilt. It was once assumed that all systems work in a similar way, but research has shown that isn’t necessarily the case.

Albrecht and his colleagues believe that, given this system has three stars, “gravitational torques from companion stars” are most likely the cause of K2-290 A’s unique rotation. The other stars in the K2-290 system might be playing havoc with the spins and orbits.
Maria Hjorth and Simon Albrecht from Aarhus University in Denmark made the discovery, and published their findings in the journal Proceedings of the National Academy of Sciences on Monday.

The two planets orbiting K2-290 A exist on the same plane, so explaining the direction difference becomes a little more complex.
“The unique aspect of K2-290 is that a companion star has been detected (K2-290 B),” read the study, “with properties that make it a good candidate for the misalignment of the protoplanetary disk.”
Planets form from the same disk of rotating material that gives birth to the star around which they move. So until now it has been assumed that any planets orbiting a star would be moving in the same direction as the star’s spin. This is certainly true in our own Solar System.
There have been a few stars discovered that spin differently to a planet that orbits them, but a recent study has found one star rotating in the opposite direction to not one, but two planets in its system.

The K2-290 system contains a total of three stars, with two planets orbiting its main star, K2-290 A. The interesting part? K2-290 A is rotating at a 124 degree tilt compared to the two planets that orbit it. Meaning it’s rotating in the opposite direction.
“The fact that [the planets] appear to be coplanar means that maybe it wasn’t a dynamically violent mechanism that caused them to migrate, maybe it was the disc,” Chris Watson of Queen’s University Belfast, told New Scientist. “So then, you have to look at how did you end up with the star and the planet-forming disc tilted in the first place?”Call it the biggest beltway ever seen. Astronomers have discovered a newly forming solar system with the inner part orbiting in one direction and the outer part orbiting the other way.

Three viewed graph showing how a counterrotating protoplanetary disk was formed.Image to right: Top view – A huge star-forming region is rotating globally in the direction shown by the white arrow. This large region can give birth to multiple stellar systems. Middle view – A detailed view inside the large star-forming region shows three protostars forming as the region collapses. The collapse process is chaotic and can cause eddies, allowing newly-forming stars to rotate in different directions and at different speeds, as shown by the arrows. Bottom view – One protostellar cloud collapses further into a disk-like structure that rotates counter-clockwise (white arrows) about the newly-formed protostar. In addition, the protostar siphons off material from a second, passing protostellar cloud rotating in the opposite direction. Because of this, the outer part of the disk rotates clockwise (yellow arrows). Eventually, planets will form from the material in this disk, with the outer planets orb

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