Groundbreaking Discovery: Mid-Infrared Flares Detected from Sgr A* for the First Time!

National Harbor, MD – Utilizing the James Webb Space Telescope (JWST), a group of scientists led by astronomers from the Center for Astrophysics | Harvard & Smithsonian (CfA) discovered a Mid-Infrared (mid-IR) flare emanating from the supermassive black hole (SMBH) at the center of the Milky Way galaxy for the very first time. In concurrent observations, the team located a radio counterpart flare that was delayed.

Researchers have been diligently monitoring Sgr A*— a SMBH approximately 4 million times the mass of the Sun— since the early 1990s. Sgr A* frequently displays flares that can be detected in various wavelengths, allowing scientists to observe different perspectives of the same flare. This feature also aids them in comprehending how it produces flares and the timescales over which they happen. Despite a long history of fruitful observations, counting imaging of this cosmic entity by the Event Horizon Telescope in 2022, one vital aspect of the puzzle— mid-IR observations— remained absent until now.

Infrared light represents a form of electromagnetic radiation. It possesses longer wavelengths than visible light but shorter than radio light. Mid-IR occupies the intermediate region of the IR spectrum, enabling astronomers to scrutinize objects, like flares, that are often challenging to detect in other wavelengths due to dense dust. Prior to the recent investigation, no team had successfully recorded Sgr A*’s variability within the mid-IR range, resulting in a gap in scientists’ understanding of the mechanisms behind flares and uncertainty regarding the completeness of their theoretical models.

“The flare from Sgr A* evolves and transforms rapidly, within a span of hours, and not all variations can be captured at every wavelength,” expressed Joseph Michail, one of the primary authors of the study and an NSF Astronomy and Astrophysics Postdoctoral Fellow at the Smithsonian Astrophysical Observatory, part of the CfA. “For over 20 years, we have monitored what occurs in the radio and Near-infrared (NIR) ranges, but the relationship between them has never been fully clarified. This recent mid-IR observation bridges that gap.”

Researchers are not entirely certain about the origin of flares, thus they depend on models and simulations, comparing these with observations to gain insights into their causes. Numerous simulations indicate that the flares seen in Sgr A* result from the interactions of magnetic field lines within the SMBH’s turbulent accretion disk. When two magnetic field lines draw near to one another, they can connect and discharge a significant amount of energy. A byproduct of this magnetic reconnection is synchrotron emission. The emission observed in the flare amplifies as energized electrons traverse the SMBH’s magnetic field lines at velocities approaching the speed of light.

Michail stated, “Because mid-IR resides between the submillimeter and the NIR, it concealed secrets regarding the role of electrons, which must cool off to release energy that fuels the flares. Our recent observations align with existing models and simulations, providing one more solid piece of evidence to support the theory behind the flares.”

Simultaneous observations with the SAO’s Submillimeter Array— a facility of the CfA, NASA’s Chandra X-ray Observatory (operated by the SAO), and NASA’s Nuclear Spectroscopic Telescope Array (NuSTAR) added another layer to the narrative. No flare was observed during the X-ray studies, likely because this specific flare did not energize electrons to the levels reached by other flares. However, the team struck gold when they focused on the SMA, which detected a millimeter (mm) flare lagging approximately 10 minutes behind the mid-IR flare.

“Our findings suggest there might be a correlation between the observed mm-variability and the detected MIR flare emission,” stated Sebastiano D. von Fellenberg, a postdoctoral researcher at the Max Planck Institute for Radio Astronomy (MPIfR) and the ” leading author of the new paper. He emphasized that these results highlight the significance of broadening multi-wavelength studies not just for Sgr A*, but for other SMBHs, such as M87*, to gain a comprehensive understanding of what truly occurs within and beyond their accretion discs.

“While our findings imply that the mid-IR emission from Sgr A* indeed results from synchrotron emissions from cooling electrons, there remains much to comprehend about magnetic reconnection and turbulence in Sgr A*’s accretion disk,” mentioned von Fellenberg. “This inaugural mid-IR detection, paired with the variability observed through the SMA, has not only bridged a gap in our understanding of what triggered the flare in Sgr A*, but also opened up a new avenue for vital research.”

Michail added, “We still seek to uncover… what other mysteries does Sgr A* conceal that the mid-IR can illuminate? What is the true nature behind the flare’s variable emissions? There is a treasure trove of knowledge embedded within this black hole’s vicinity just waiting for our exploration.”

The latest observations were revealed today during a press conference at the 245th gathering of the American Astronomical Society (AAS) in National Harbor, Maryland, and are slated for publication in the Astrophysical Journal Letters (ApJL).

Situated near the peak of Maunakea on the Big Island of Hawaii, the Submillimeter Array (SMA) ranks among the premier observatories of the CfA. The observatory comprises eight radio dishes collaborating as a single telescope, granting astronomers a viewpoint on a broad assortment of astronomical entities and events: planets and comets in our own Solar System; the formation of stars and planets; and the supermassive black holes concealed at the cores of the Milky Way and other galaxies. The SMA is co-managed by the CfA and the Academia Sinica in Taiwan.

A different version of this press release was released by the Max Planck Institute for Radio Astronomy (MPIfR). 

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The Center for Astrophysics | Harvard & Smithsonian is a partnership between Harvard and the Smithsonian aimed at inquiring—and ultimately solving—humanity’s most significant unanswered questions regarding the essence of the universe. The Center for Astrophysics is based in Cambridge, MA, with research facilities across the U.S. and globally.

Resource:

von Fellenberg, S., Roychowdhury, T., Michail, J. et al. “First mid-infrared detection and modeling of a flare from Sgr A*,” Astrophysical Journal Letters, arxiv:

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