Structure of GN20. (a) JWST/NIRCam false-color image of the gas-rich starburst galaxy GN20 at redshift z = 4.055. North is up, and east is left. (b) The 6 kpc stellar bar in the disk at rest-frame 1.1 μm light traced by JWST/MIRI, indicated by ellipses of constant brightness. (c) High-resolution submillimeter observations from the ​​​​​​NOEMA at rest-frame 220 μm reveal that the dust extends over the full stellar disk of GN20 (L. A. Boogaard et al. 2026), tracing regions of strong (obscured) star formation. (d) There is strong alignment between the stellar and dust bar. Clumps of intense star formation are visible in the nucleus, fueled by the bar funneling material to the galaxy’s center, and at the bar-disk interface to the south.