A Massive Stream of Gas Tilted This Planet-Forming Disk

A massive stream of gas, extending a trillion miles, is feeding into the circumtriple disk of the young triple star system GW Orionis, and may be responsible for tilting its disk. The streamer, detected using the Atacama Large Millimeter/submillimeter Array (ALMA), is aligned with the outermost dust ring and its angular momentum is closely aligned with this ring, suggesting it is the likely cause of the misalignment. The study, titled "A Streamer Driving Misalignment in the Circumtriple Disk of GW Ori," was led by Maria Galloway-Sprietsma, a PhD candidate at the University of Florida. The research used ALMA to piece together the details of the gas flow, which is common when measuring gas flows, as 12CO maps the full extent and velocity structure of the gas stream, while 13CO maps the densest parts of the gas stream.

The findings show that the streamer meets the disk at the outermost dust ring and that the streamer’s angular momentum vector is closely aligned with this outermost ring within ≈3∘, in contrast to the ≈32∘ misalignment with the innermost ring, suggesting the streamer is the likely cause of the misalignment. The study also highlights that the total angular momentum of the streamer is smaller than that of GW Ori’s disk, and the low accretion rate indicates the end stages of infall. The research suggests that the link between GW Ori and its parental cloud may be breaking, as the infall rate seems to be slowing.

The implications of these findings are that streamers can tilt the orbits of planets and potentially alter the rotation of stars. The study also notes that if planets form in these rings, they will be misaligned with each other due to the stream of gas. The research suggests that if these streamers are common, it can explain why planets may not necessarily end up in very orderly systems. The authors also mention that future work on shock tracers in GW Ori could help clarify the overall picture and that a systematic survey of young stars is needed to determine how many have streamers and how many don't.

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