A planetforming disc torn apart by its three central stars
A team of astronomers have identified the first direct proof that groups of stars can tear apart their planet-forming disc, which makes it warped and with tilted rings. This new study indicates exotic planets, perhaps not unlike Tatooine in Star Wars, can shape in rings that are likely in bent disks around multiple stars.
Our Solar System is unusually flat, together with the planets all orbiting in the exact same plane. But this isn’t necessarily true, particularly for planet-forming discs around multiple stars, such as the object of the new research: GW Orionis. This system, situated just over 1300 light-years away in the constellation of Orion, has three stars and a deformed, broken-apart disc surrounding them.
“Our images reveal an extreme case where the disk isn’t flat in any way, but is warped and has a misaligned ring which has broken away from the disk,” says Stefan Kraus, a professor of astrophysics at the University of Exeter in the united kingdom who led the study published in the journal Science. The misaligned ring is located in the inner area of the disc, near the 3 stars.
The new research also reveals that this inner ring contains 30 Earthmasses of dust, which could be sufficient to form planets. “Any planets formed inside the misaligned ring will orbit the star on highly oblique orbits and we predict that many planets , wide-separation orbits will probably be found in future planet imaging campaigns, for instance together with the ELT,” says group member Alexander Kreplin at the University of Exeter, speaking to ESO’s Extremely Large Telescope,which is planned to start operating later this decade. Since more than half the stars in the skies are born with one or more companions, this also raises a thrilling prospect: there might be an unknown population of exoplanets that orbit their stars on quite distant and inclined orbits Beginning in 2008, they used the AMBER and later the GRAVITY tools on ESO’s VLT Interferometer in Chile, which combines the light from different VLT telescopes, to study the gravitational dancing of the three stars from the machine and map their own orbits. “We found that the three stars do not orbit in the same airplane, but their orbits are misaligned with respect to one another and with respect to the disk,” says Alison Young of the Universities of Exeter and Leicester and also a part of the group.
They also observed that the system with the SPHERE instrument on ESO’s VLT and with ALMA, where ESO is a spouse, and were able to picture the internal ring and affirm its misalignment. ESO’s SPHERE also let them view, for the very first time, the shadow that this ring casts on the remaining portion of the disc. This helped them find out the 3D form of the ring and the overall disc.
The global team, including researchers from the UK, Belgium, Chile, France and the US, then combined their exhaustive observations together with computer simulations to understand what had occurred to the system. For the first time, they were able to clearly connect the observed misalignments to the theoretical”disctearing impact”, which implies the contradictory gravitational pull of celebrities in different planes can warp and divide their disks.
Their simulations showed that the misalignment in the orbits of the three celebrities could create the disk about them to split into distinct rings, and that is precisely what they see in their own observations. The observed shape of the inner ring also matches forecasts from numerical simulations on the way in which the disc would tear.
Interestingly, another team who analyzed the exact same system using ALMA consider another ingredient is needed to understand the system. “We think the presence of a world between those earrings is required to explain why the disc ripped apart,” states Jiaqing Bi of the University of Victoria in Canada who led a study of GW Orionis published in The Astrophysical Journal Letters in May this year. His team identified three dust rings in the ALMA observations, together with the ring being the largest ever observed in planet-forming discs. Future observations with ESO’s ELT along with other telescopes may help astronomers completely unravel the character of GW Orionis and show young planets forming across its three stars.