Three Stars Spotted Ripping Apart Their Planet-Forming Disk In An Incredible Way

Artist impression (left) of what the true image of the core of GW Orionis (right) looks like.  ESO/L. Calçada, Exeter/Kraus et al.

Astronomers have discovered for the first time peculiar structures surrounding three stars that show they are tearing apart their planet-forming disk. These young objects in the GW Orionis system have dramatically warped the disk of material from which planets might be born, creating tilting misaligned rings.

The incredible findings are reported in Science and in The Astrophysical Journal Letters by two independent teams, using the combined power of the European Southern Observatory’s Very Large Telescope (VLT) and the Atacama Large Millimeter/submillimeter Array (ALMA) to probe the peculiar geometry of this system.

The system is located about 1,300 light-years away in the constellation of Orion. Two stars orbit each other every 241 days, with the third one going around the other two in 11.5 years.

The simulations from the first team suggest that a misalignment in the orbits of the three stars has created the warp in the once-flat disk. Observations using the VLT's SPHERE instrument allowed them to reconstruct the disk in three-dimensions by revealing the shadow of the innermost ring on the rest of the disk, making it obvious that the inner portion is dramatically warped and that a ring at an even steeper angle separated from it.

"In our images, we see the shadow of the inner ring on the outer disk. At the same time, ALMA allowed us to measure the precise shape of the ring that casts the shadow. Combining this information allows us to derive the 3-dimensional orientation of the misaligned ring and of the warped disk surface," explained lead author of the first study, Stefan Kraus, a professor of astrophysics at the University of Exeter in the UK, in a statement.

Most stars have flat planet-forming disks but GW Orionis features a warped disk, deformed by the movements of the three stars at its center. The ALMA image (left) shows the disk’s ringed structure, with the innermost ring separated from the rest. The SPHERE observations (right) allowed astronomers to see for the first time the shadow of this innermost ring on the rest of the disk, which made it possible for them to reconstruct its warped shape in 3D. ALMA (ESO/NAOJ/NRAO), ESO/Exeter/Kraus et al.

The system features many curiosities of interest to astronomers. The outer ring is the largest one ever seen in a planet-forming disk. The inner misaligned ring contains 30 Earth-masses worth of dust, which would certainly be enough to form a planet. According to one team, there might already be planets there.

“We think that the presence of a planet between these rings is needed to explain why the disk tore apart,” said Jiaqing Bi, lead author of the second paper, in a statement. Further exploration of GW Orionis will be needed to confirm this.



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