The research was initially presented at a press conference during the American Astronomical Society’s 247th meeting and has now been accepted for publication in The Astrophysical Journal. The paper is available on the arXiv preprint server.
Charles Law, an assistant professor at the University of Minnesota and the principal investigator of the research, said GoHam provides an unusually clear view of the vertical and radial structure of a very large, nearly edge-on disk.
“GoHam gives us a rare and clear view of the vertical and radial structure of a very large, nearly edge-on disk,” Law said.
He added that the system could serve as a benchmark for testing detailed models of how planets form and evolve within disks. Its extreme size, pronounced asymmetries, winds and potential planet formation make it a valuable laboratory for investigating how giant planets can form far from their host star and how their presence alters the surrounding gas and dust.
ALMA observations have enabled researchers to examine the different layers of gas and dust as they rotate around the young star. Because the disk is oriented almost edge-on, astronomers can directly study its vertical structure, an observation that is considerably more difficult in other planet-forming disks.
Using millimeter-wavelength observations, the team mapped millimeter-sized dust grains and several gas-phase molecules across the disk. These include two forms of carbon monoxide, along with the sulfur-bearing molecules carbon monosulfide (CS) and sulfur monoxide (SO).
The distribution of these materials broadly follows the expected pattern of vertical stratification. The lightest gas tracer, ¹²CO, lies highest above the disk’s midplane, while ¹³CO is found somewhat lower. CS gas is concentrated closest to the midplane, consistent with astronomers’ understanding of how gas layers are distributed within disks.
The millimeter-sized dust grains occupy a relatively thin layer concentrated around the midplane, while gas extends much farther above and below it. This contrast reveals how vertically extended the gaseous component is compared with the larger solid particles.
However, the disk does not have a perfectly symmetrical structure. Its millimeter dust emission is unevenly distributed from north to south, with one side showing brighter and more extended emission than the other. Researchers suggest that a vortex or another large-scale disturbance could explain this asymmetry. Such a structure could trap solid particles, potentially supplying material for planet formation.
The team also detected faint, extended and wispy carbon monoxide emission in the northern region of the disk and at large distances from the star. This feature could be consistent with a photoevaporative wind, a process in which starlight gradually drives gas away from the disk and into space.
Another unusual feature is a one-sided arc of sulfur monoxide (SO) emission located just beyond the disk’s bright dust region. Although the arc appears on only one side, its motion remains consistent with the disk’s rotation.
The SO arc aligns with a previously identified dense clump known as “GoHam b.” Researchers believe the clump may consist of material collapsing under its own gravity, potentially representing one of the earliest observable stages of a massive planet forming on a wide orbit in the outer disk.
The scale of GoHam further distinguishes it from typical planet-forming systems. Its ¹²CO gas extends to a radius of almost 1,000 astronomical units, while the disk reaches vertical heights of several hundred astronomical units. These dimensions place it among the largest known planet-forming disks.
Researchers also estimate that its total dust mass is many times greater than that of typical disks around similar stars. This substantial reservoir of material gives the system considerable potential to form giant planets and possibly develop into a multiplanet system.
Together, the disk’s immense size, layered gas and dust, north–south asymmetry, possible wind activity and the unusual GoHam b clump make it an important system for examining the conditions under which giant planets may emerge far from their host stars. The observations provide astronomers with a detailed opportunity to test models of planet formation and understand how developing planets can reshape their surrounding environments.
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