Resolved Magnetic-Field Structure and Variability Near the Event Horizon of Sagittarius A*

TL;DR

This paper presents high-resolution interferometric observations of Sagittarius A* that reveal partially ordered magnetic fields near the event horizon and detect intra-hour variability, advancing understanding of black hole accretion and jet formation.

Contribution

First direct imaging of magnetic field structure near a black hole's event horizon at horizon-scale resolution.

Findings

Partially ordered magnetic fields detected near the event horizon.

Intra-hour variability localized to the region close to the black hole.

Magnetic field structures observed on scales of about 6 Schwarzschild radii.

Abstract

Near a black hole, differential rotation of a magnetized accretion disk is thought to produce an instability that amplifies weak magnetic fields, driving accretion and outflow. These magnetic fields would naturally give rise to the observed synchrotron emission in galaxy cores and to the formation of relativistic jets, but no observations to date have been able to resolve the expected horizon-scale magnetic-field structure. We report interferometric observations at 1.3-millimeter wavelength that spatially resolve the linearly polarized emission from the Galactic Center supermassive black hole, Sagittarius A*. We have found evidence for partially ordered fields near the event horizon, on scales of ~6 Schwarzschild radii, and we have detected and localized the intra-hour variability associated with these fields.