Astronomers Unveil Strong Magnetic Fields Spiraling at the Edge of Milky Way’s Central Black Hole

Credit: EHT Collaboration

The Event Horizon Telescope (EHT) collaboration has observed spirals of light escaping from the edge of the supermassive black hole at the center of our Milky Way Galaxy. Seen in polarized light for the first time, this new view of Sagittarius A* (Sgr A*) has revealed a structure strikingly similar to that of the black hole at the center of the M87 galaxy, suggesting that strong magnetic fields may be common to all black holes. This similarity also hints toward a hidden jet in Sgr A*. The results were published in The Astrophysical Journal Letters.

The Atacama Large Millimeter/submillimeter Array (ALMA) helped astronomers to discover this new finding. ALMA is the world’s most powerful millimeter/ submillimeter telescope, and an important instrument for the EHT. The spiraling light at the heart of this research is actually made up of radio waves—light that can’t be seen by the human eye or optical telescopes, but can be observed by the many radio telescopes, including ALMA, working together across the EHT.

Scientists unveiled the first image of Sgr A*—which is approximately 27,000 light-years away from Earth—in 2022, revealing that while the Milky Way’s supermassive black hole is more than a thousand times smaller and less massive than M87’s, it looks remarkably similar. This made scientists wonder whether the two shared common traits outside of their looks. To find out, the team decided to study Sgr A* in polarized light. Previous studies of light around M87* revealed that the magnetic fields around the black hole giant allowed it to launch powerful jets of material back into the surrounding environment. Building on this work, the new images have revealed that the same may be true for Sgr A*.

Read more at the Center for Astrophysics | Harvard & Smithsonian, USA.

About the EHT

The EHT collaboration involves more than 300 researchers from Africa, Asia, Europe, and North and South America. The international collaboration is working to capture the most detailed black hole images ever obtained by creating a virtual Earth-sized telescope. Supported by considerable international investment, the EHT links existing telescopes using novel systems — creating a fundamentally new instrument with the highest angular resolving power that has yet been achieved.

The individual telescopes involved in the EHT in April 2017, when the observations were conducted, were: the Atacama Large Millimeter/submillimeter Array (ALMA), the Atacama Pathfinder EXperiment (APEX), the Institut de Radioastronomie Millimetrique (IRAM) 30-meter Telescope, the James Clerk Maxwell Telescope (JCMT), the Large Millimeter Telescope Alfonso Serrano (LMT), the Submillimeter Array (SMA), the UArizona Submillimeter Telescope (SMT), the South Pole Telescope (SPT). Since then, the EHT has added the Greenland Telescope (GLT), the IRAM NOrthern Extended Millimeter Array (NOEMA) and the UArizona 12-meter Telescope on Kitt Peak to its network.

The EHT consortium consists of 13 stakeholder institutes: the Academia Sinica Institute of Astronomy and Astrophysics, the University of Arizona, the University of Chicago, the East Asian Observatory, Goethe-Universitaet Frankfurt, Institut de Radioastronomie Millimétrique, Large Millimeter Telescope, Max Planck Institute for Radio Astronomy, MIT Haystack Observatory, National Astronomical Observatory of Japan, Perimeter Institute for Theoretical Physics, Radboud University and the Smithsonian Astrophysical Observatory.


The Atacama Large Millimeter/submillimeter Array (ALMA), an international astronomy facility, is a partnership of the European Organisation for Astronomical Research in the Southern Hemisphere (ESO), the U.S. National Science Foundation (NSF) and the National Institutes of Natural Sciences (NINS) of Japan in cooperation with the Republic of Chile. ALMA is funded by ESO on behalf of its Member States, by NSF in cooperation with the National Research Council of Canada (NRC) and the Ministry of Science and Technology (MOST) and by NINS in cooperation with the Academia Sinica (AS) in Taiwan and the Korea Astronomy and Space Science Institute (KASI).

ALMA construction and operations are led by ESO on behalf of its Member States; by the National Radio Astronomy Observatory (NRAO), managed by Associated Universities, Inc. (AUI), on behalf of North America; and by the National Astronomical Observatory of Japan (NAOJ) on behalf of East Asia. The Joint ALMA Observatory (JAO) provides the unified leadership and management of the construction, commissioning and operation of ALMA.

The National Radio Astronomy Observatory (NRAO) is a facility of the National Science Foundation, operated under cooperative agreement by Associated Universities, Inc.

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