Trillion-mile gas streamer may explain tilt of triple-star system's outer planet-forming ring

Astronomers have discovered a colossal stream of gas, measuring one trillion miles or 0.2 light-years, flowing towards the young triple-star system GW Orionis. Utilizing the Atacama Large Millimeter/submillimeter Array (ALMA), the researchers observed this gas streamer, which provides compelling evidence for how "streamers" can tilt and alter the disks where planets form.

GW Orionis, situated 1,300 light-years away in the Orion constellation, boasts three stars surrounded by multiple rings of planet-forming material. These rings are notably tilted at various angles, making GW Orionis an ideal target for studying the formation of unusual planetary architectures. By measuring the streamer's movement and comparing its angular momentum to the system's ring orientations, the team led by Maria Galloway-Sprietsma found that the streamer's trajectory aligns closely with the outer dust ring but is significantly misaligned with the inner ring.

This discovery suggests a direct link between the infalling material and the outer ring's tilted state. Previous studies indicated that GW Orionis' inner, middle, and outer rings are misaligned, each tilted at different angles. The newly measured data supports a more dynamic picture of planetary system formation, where turbulent streamers from the surrounding environment can reshape disks late in their evolution, potentially setting planets on tilted or even opposite orbital paths to their host star's spin.

The ALMA's high-resolution capabilities were crucial in this study. The 12-meter, 7-meter, and Total Power arrays of ALMA enabled the researchers to zoom out and observe the full extent of the streamer while simultaneously modeling the misalignments of the rings. The molecular lines of 12CO and 13CO detected with ALMA revealed that the streamer's total angular momentum is much lower than that of the GW Orionis disk, indicating that the dynamics of this system likely represent later stages of the infall phenomenon.

With ALMA's sensitivity, the researchers were able to study the kinematics of the streamer, finding that the streamer's angular momentum is insufficient to further misalign the disk. This finding implies that the streamer once had a higher angular momentum, allowing the disk to become misaligned in the past. Future ALMA observations of GW Orionis aim to identify shock-tracing molecules, such as sulfur-bearing species, to pinpoint precisely where the streamer collides with the disk and how this impact shapes the material available for planet formation.