The superclouds of the local Milky Way

¹ University of Vienna, Department of Astrophysics, Türkenschanzstrasse 17, 1180 Wien, Austria
² Max-Planck Institut für Astrophysik, Karl-Schwarzschild-Str. 1, 85748 Garching, Germany
³ Ludwig-Maximilians-Universität München (LMU), Geschwister-Scholl-Platz 1, 80539 München, Germany
⁴ Deutsches Zentrum für Astrophysik, Postplatz 1, 02826 Görlitz, Germany
⁵ Excellence Cluster ORIGINS, Boltzmannstr. 2, 85748 Garching, Germany

^★ Corresponding author: This email address is being protected from spambots. You need JavaScript enabled to view it.

Received: 17 July 2025
Accepted: 3 December 2025

Abstract

Recent 3D dust maps of the local Milky Way are revolutionizing our understanding of the Sun’s Galactic neighborhood, providing much needed insight into the large-scale organization of the interstellar medium. Focusing on the largest scales in Gaia-based 3D dust maps, we find a pattern of seven highly elongated, mostly parallel structures in the local ∼5 kpc², five of which were previously unknown. These structures show pitch angles of 33.5 ± 4.0^◦ and masses ranging from 10⁵ to 10⁶ M_⊙. We refer to these structures as superclouds. Nearly all known star-forming regions in the solar neighborhood lie within the superclouds, primarily along their central axes, supporting the idea that they act as gas reservoirs for the formation of giant molecular clouds. All but one of the seven superclouds show an underlying undulation, indicating that this is not a property unique to the Radcliffe Wave. We find that while the superclouds have linear masses that vary by about a factor of 4, their volume densities only vary by about 10%. This suggests that superclouds self-regulate their physical sizes and internal structure to maintain pressure equilibrium with their environment. These findings establish a new framework for understanding how large-scale Galactic structures shape the conditions for star formation in the solar vicinity, and likely in galaxies like the Milky Way.