Shaping Outflows and Jets by Ambient Pressure: A Unified Framework

Abstract Astrophysical outflows are ubiquitous across cosmic scales, from stellar to galactic systems. While diverse launching mechanisms have been proposed, we demonstrate that these outflows share a fundamental commonality: their morphology follows the physics of pressure-confined supersonic flows. By extending classical de Laval nozzle theory to account for ambient pressure gradients, we present a unified framework that successfully describes outflows from young stellar objects to active galactic nuclei. This simplified approach, compared to full magnetohydrodynamic treatments, captures the essential physics governing outflow shapes across different scales. Our model reveals a remarkable consistency of pressure profiles, characterized by a power-law exponent near “–2” across 6 orders of magnitude in spatial scale, independent of the internal characteristics of the outflow or the nature of the central engine. This discovery suggests a universal mechanism for outflow collimation and acceleration, bridging the gap between theoretical models and observational features across a wide range of astronomical scales.