Cosmic ‘hamburger’ offers rare edge-on view of where giant planets may take shape

Astronomers using the Atacama Large Millimeter/submillimeter Array (ALMA) were surprised to discover the earliest phases of giant planet formation between the dense layers of gas and dust in the “Gomez’s Hamburger” system, referred to as GoHam.

This research was initially shared at a press conference at the American Astronomical Society’s 247th meeting and has just been accepted for publication in The Astrophysical Journal. The paper is available on the arXiv preprint server.

So how does this celestial slider impact astronomers’ understanding of planet formation? “GoHam gives us a rare and clear view of the vertical and radial structure of a very large, nearly edge‑on disk,” shares Charles Law, an assistant professor at the University of Minnesota and principal investigator on this research.

He notes that “This makes it a benchmark system for testing detailed models of how planets form and evolve in disks. 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.”

Sweet, sweet gas (and dust)

While “gas” and “dust” are normally pretty low on most people’s priority lists, they are very important to astronomers. This is what GoHam’s giant disk is made of, and astronomers are able to observe these stacked layers as they rotate around a young star at an almost edge-on orientation. This gives them a direct view of its vertical structure (something that’s much harder to see in other disks).

Thanks to ALMA observations at millimeter wavelengths, scientists can clearly map the location of the millimeter-sized dust grains and several different gas-phase molecules within the layers. These include two forms of carbon monoxide and the sulfur-bearing molecules CS and SO.

So where are these little guys? Behaving as expected, the lightest gas (¹²CO) sits highest above the midplane, while ¹³CO sits a bit lower, and the CS gas lies closest to the midplane, following astronomers’ understanding of how disks stratify with height. And we mustn’t forget the dust! The millimeter dust itself is relatively thin and concentrated in the midplane, while the gas extends far above and below, showing just how “puffed up” the gaseous part of the disk is compared to the larger solids.

Can I get a side of sulfur monoxide with that?

This is not a perfect hamburger. GoHam’s millimeter dust is lopsided north–south: one side of the disk has more extended and brighter dust emission, due to a vortex or large‑scale disturbance that could help trap solids, providing more food for planet formation.

Faint, extended, and wispy carbon monoxide emission appears in the northern part of the disk and at large distances, potentially consistent with a “photoevaporative wind” in which starlight is slowly blowing gas off the disk into space.

The team also found an unusual, one‑sided arc of sulfur monoxide (SO) emission just outside the bright dust on only one side of the disk, but with kinematics that still follow the disk’s rotation. This SO arc lines up with a previously identified dense clump called “GoHam b,” thought to be material collapsing under its own gravity and possibly representing one of the earliest observable stages of a massive, wide‑orbit planet forming in the outer disk.

That’s one big burger

GoHam is a supersized order: the disk is enormous (and massive) with its ¹²CO gas stretching out to almost 1,000 astronomical units in radius and reaching 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, which means GoHam has huge potential to build giant planets and possibly a future multiplanet system.

Who’s behind this story?

Swati Mestri

Swati Mestri holds a bachelor’s degree in Electronics Engineering and has worked as a content editor since 2019. She has experience editing research documents across technology, health care, and materials science, and has a particular interest in technology and space.

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Robert Egan

Bachelor’s in mathematical biology, Master’s in creative writing. Well-traveled with unique perspectives on science and language.

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