Maciek Wielgus3 Pratul P. Srinivasan4
1California Institute of Technology 2Princeton 3Max-Planck-Institut für Radioastronomie 4Google DeepMind
To reconstruct the 3D strcuture around a black hole, we developed a new computational tool which we call: Orbital Polarimetric Tomography. Orbital tomography relies on constraining a neural representation ("Neural Radiance Field") with general relativistic ray tracing. This figure gives an overview of the main computational components: 1. An orbital model propagates an initial emission volume (e0) in time. 2. Ray tracing: we compute General Relativistic ray paths according to the black hole parameters (spin, mass, inclination) and numerically integrate the 3D emissivities to synthesize image plane frames. 3. Each frame is summed to produce a single light curve data point which downstream is compared to the observations. 4. A neural representation captures the underlying 3D volume as a continuous function.
Abstract
The interaction between the supermassive black hole at the center of the Milky Way, Sagittarius A∗, and its accretion disk occasionally produces high-energy flares seen in X-ray, infrared, and radio. One proposed mechanism that produces flares is the formation of compact, bright regions that appear within the accretion disk and close to the event horizon. Understanding these flares provides a window into accretion processes. Although sophisticated simulations predict the formation of these flares, their structure has yet to be recovered by observations. Here we show the first three-dimensional (3D) reconstruction of an emission flare recovered from ALMA light curves observed on April 11, 2017. Our recovery shows compact, bright regions at a distance of roughly six times the event horizon. Moreover, it suggests a clockwise rotation in a low-inclination orbital plane, consistent with prior studies by GRAVITY and EHT. To recover this emission structure, we solve an ill-posed tomography problem by integrating a neural 3D representation with a gravitational model for black holes. Although the recovery is subject to, and sometimes sensitive to, the model assumptions, under physically motivated choices, our results are stable, and our approach is successful on simulated data.
Research Briefing [Nature Astronomy] paper [arXiv] code [Github] DOI: 10.1038/s41550-024-02238-3
Citation
A. Levis, A. A. Chael, K. L. Bouman, M. Wielgus, P. P. Srinivasan. "Orbital Polarimetric Tomography of a Flare Near the Sagittarius A* Supermassive Black Hole." Nature Astronomy, 2024.
@article{levis2024orbital,
title={Orbital polarimetric tomography of a flare near the Sagittarius A* supermassive black hole},
author={Levis, Aviad and Chael, Andrew A and Bouman, Katherine L and Wielgus, Maciek and Srinivasan, Pratul P},
journal={Nature Astronomy},
volume={8},
number={6},
pages={765--773},
year={2024}
publisher={Springer Nature}
}
Visualizations
The visualization below illustrate the recovery results:
a) The recovered 3D structure visualized from the estimated Earth view (12 degree inclination).
a) The recovered 3D structure is fixed in time, with the view rotating to help visualize the structure from all angles.
b) The recovered 3D structure at a fixed view angle as the orbital model evolves over a span of ~100 minutes
Below is an (approximate) interactive visualization of what the 3D emission structure around Sagittarius A* might look like. The emission was reconstructed from observations of the Atacama Large Millimeter Array, taken on April 11, 2017, directly after a flare was detected in X-ray. The 3D structure features two bright, compact features located about 75 million kilometers (or half the distance between Earth and the Sun) from the center of the black hole. For size comparison we illustrate the black hole event horizon and three concentric rings at distances of 6M (innermost stable circular orbit of a non-spinning black hole), 10M, and 20M or alternatively approximately 36, 60, 120 million kilometers.
Loading interactive 3D visualization : 0/?
Media
[space.com] Scientists use AI to reconstruct energetic flare blasted from Milky Way's supermassive black hole
[Sky&Telescope] Watch a Hotspot Orbit Our Galaxy's Black Hole
[Intesting Engineering, MSN] Video: Caltech develops first 3D model of black hole’s mysterious flare
[ZME Science] Astronomers reveal 3-D structure of rotating flares from Milky Way’s supermassive black hole
[Live Science] Explosive black hole flare from the center of our galaxy reconstructed from 'a single flickering pixel' using AI and Einstein's equations
[Quantum Zeitgeist] Caltech Scientists Use AI to Unveil 3D Video of Flares Around Milky Way’s Black Hole"
[Science Friday] Visualizing A Black Hole’s Flares In 3D"
[themosaic] The Art of Astrophysics Virtual Exhibition