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James Webb Space Telescope captures new mid-infrared flare from Milky Way black hole
James Webb Space Telescope observes mid-infrared flare from Milky Way’s central black hole, Sagittarius A*, revealing flare evolution, synchrotron cooling, and magnetic field measurements.
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In this handout photo provided by NASA, This is the first image of Sgr A*, the supermassive black hole at the centre of our galaxy, with an added black background to fit wider screens (Image via Getty)The James Webb Space Telescope (JWST) has detected a mid-infrared flare from Sagittarius A*, the supermassive black hole at the center of the Milky Way, marking the first observation of such activity in this wavelength.
Previous studies had identified flares in near-infrared and radio wavelengths but mid-infrared data were absent.
According to the team led by Sebastiano von Fellenberg of the Max Planck Institute for Radio Astronomy in Bonn, Germany, these observations help bridge the spectral gap between infrared and radio measurements.
The data provide new insight into flare evolution and allow the measurement of physical parameters such as magnetic field strength.
The team employed JWST's Mid-Infrared Instrument (MIRI) in its Medium-Resolution Spectrometer (MRS) mode to study the flare.
Earth-based telescopes cannot offer very sensitive mid-infrared readings due to the Earth’s atmosphere, which disrupts these wavelengths.
The mid-infrared flare showed features similar to near-infrared flares, thus confirming that flare activity happens in both wavelengths.
By using MIRI, scientists were able to record the mid-infrared spectral index for the very first time.
Such a measurement gives details about the energy distribution during the flare and it also confirms the occurrence of synchrotron cooling, where electrons with very high speed lose their energy by emitting synchrotron radiation.
The spectral index is also enabling the researchers to determine the magnetic field strength in the flare region much more directly than it would be possible with only near-infrared observations.
Characteristics of the flares
According to NASA, Sagittarius A* produces flares continuously with no periods of inactivity and the flares vary in intensity and duration.
JWST’s Near-Infrared Camera (NIRCam) was used to observe 48 hours of activity in 8 to 10 hour increments over the course of a year.
Researchers found short, faint flickers lasting seconds, longer bright eruptions occurring daily and even smaller changes developing over months.
Observations showed that brightness changes at shorter wavelengths precede those at longer wavelengths by a few seconds to 40 seconds.
This time delay indicates that particles lose energy at different rates depending on the wavelength, consistent with synchrotron radiation and particle motion along magnetic field lines.
Mechanisms behind the flares
Astrophysicists have singled out two distinct mechanisms that possibly combine to produce the flare activity of Sgr A*.
It is imagined that small perturbations in the accretion disk, for instance, turbulent fluctuations compressing plasma, give rise to a short burst of radiation resembling solar flares.
Big, more brilliant flares, on the other hand, are explained by the magnetic reconnection hypothesis when colliding magnetic fields release energy and accelerate particles to nearly light speed.
These explosions emit bursts of synchrotron radiation that can be detected at various wavelengths.
JWST-facilitated concurrent multi-wavelength observations help scientists to separate variables like magnetic field strength from electron number density and other parameters, thus giving them a more accurate data set for their theoretical models of black hole environments.
Significance of the observations
The JWST observations represent the first continuous, multi-wavelength dataset of Sgr A* flares in the mid-infrared.
The data fills a spectral gap between infrared and radio observations, providing a clearer view of flare evolution and energy distribution.
According to von Fellenberg, the high sensitivity of JWST and the broad wavelength coverage of MIRI are prerequisites for measuring the spectral index and confirming synchrotron cooling behavior.
The research, including two companion papers, is available on arXiv.
These observations provide a foundation for further studies of supermassive black holes, the dynamics of accretion disks and the influence of magnetic fields on flare activity, as reported by Space.com and NASA.
Stay tuned for more updates.
TOPICS: James Webb Space Telescope, black hole flares, JWST mid-infrared flare, Milky Way black hole, Sagittarius A*, Sgr A* observations