ALMA views giant dusty disk in Gomezs Hamburger with signs of early giant planet formation

by Clarence Oxford
Los Angeles CA (SPX) Jan 06, 2026

Astronomers using the Atacama Large Millimeter/submillimeter Array ALMA have identified the earliest phases of giant planet formation inside the dense layers of gas and dust in the nearly edge-on disk known as Gomez's Hamburger GoHam. The team presented the research, which is in preparation for publication, at a press conference during the American Astronomical Society's annual meeting in January.

GoHam's disk surrounds a young star and is oriented almost edge-on, allowing a direct view of its vertical structure as the material rotates. ALMA observations at millimeter wavelengths map the millimeter-sized dust grains and multiple gas-phase molecules, revealing how they are arranged in distinct layers within the disk.

The observations detect two isotopologues of carbon monoxide along with sulfur-bearing molecules CS and SO. Emission from 12CO appears highest above the midplane, 13CO lies lower, and CS is concentrated closest to the midplane, matching expectations for how disk material stratifies with height. The millimeter dust forms a relatively thin, midplane layer, while gas extends to several hundred astronomical units above and below, showing that the gaseous component is much more extended than the larger solids.

GoHam is described as a supersized disk: 12CO emission traces gas to almost 1,000 astronomical units in radius and to vertical heights of several hundred astronomical units, making it one of the largest known planet-forming disks. The total dust mass is estimated to be many times higher than in typical disks around similar stars, indicating substantial material available to build giant planets and possibly a multi-planet system.

The disk is not symmetric. GoHam's millimeter dust emission is brighter and more extended on one side in the north - south direction, a pattern attributed to a vortex or large-scale disturbance that can trap solids and concentrate material for planet formation. Faint, extended carbon monoxide emission in the northern part of the disk and at large distances matches expectations for a photoevaporative wind, in which starlight gradually drives gas off the disk into space.

The team also reports a one-sided arc of sulfur monoxide emission just outside the bright dust on only one side of the disk. This SO feature shares the disk's rotational kinematics and lines up with a dense clump previously labeled GoHam b, which is thought to be collapsing under its own gravity and may represent one of the earliest observable stages of a massive planet forming on a wide orbit in the outer disk.

According to principal investigator Charles Law, an NHFP Sagan Fellow at the University of Virginia, "GoHam gives us a rare and clear view of the vertical and radial structure of a very large, nearly edge-on disk." He adds that "This makes it a benchmark system for testing detailed models of how disks evolve and form planets. The combination of extreme disk size, strong asymmetries, winds, and potential planet formation makes it the perfect laboratory for understanding how giant planets can form far from their star, and how their presence reshapes the surrounding gas and dust."