Sagittarius A*: Cosmic fireworks light up Milky Way center
The supermassive black hole at the centre of our galaxy, the Milky Way, while not as "voracious" as others known on the outskirts of the universe, is surrounded by spectacular "fireworks" — new data from the Webb Space Telescope reveals.
The latest data from the James Webb Space Telescope (JWST) show that the environment around the black hole pulses with "fireworks." Scientists have analyzed strange bursts that appear around the supermassive black hole Sagittarius A* in the central part of our Milky Way galaxy. Telescope readings in two near-infrared bands reveal cosmic bursts that vary in brightness and duration.
Five to six bursts per day around the black hole
According to scientists, the disk full of scattered materials and hot gas surrounding the black hole generates five or six large bursts per day, with several smaller explosions in between. These observations have been detailed in the scientific edition of the journal "The Astrophysical Journal Letters."
The data indicates that dynamically changing brightness often increases in sudden bursts, only to recede again — as noted during research conducted by Farhad Yusef-Zadeh from Northwestern University. The observed profile of the black hole's activity turned out to be quite random and new each time.
Yusef-Zadeh and his team studied Sagittarius A* with the near-infrared camera (NIRCam) for 48 hours, expecting to see bursts. Although they knew such flares might appear, they did not anticipate how intense the activity surrounding the black hole would be.
What causes the bursts around the black hole?
Researchers suggest that two separate processes may cause this light show. Smaller flares may result from turbulence in the disk spinning around the black hole, which, by compressing hot, magnetized gas, may generate short bursts of radiation, comparable to solar flares.
Large explosions, on the other hand, may result from magnetic reconnection (a phenomenon where magnetic field lines from different regions connect, leading to the release of a large amount of energy), when colliding magnetic fields eject particles at speeds close to the speed of light. Similar to the sparking of static electricity, this process generates a "reconnection spark."
The unexpected aspect was also how the brightness of the bursts changed at two different wavelengths — scientists note. It was observed that events in shorter wavelengths changed brightness slightly faster than those in longer ones. This may provide clues about the physical processes occurring in the disk around the black hole. Likely, particles from the flares lose energy more quickly at shorter wavelengths, as expected for particles swirling around magnetic field lines.
Researchers will continue to track the mysterious bursts
Now researchers aim to obtain longer observation periods with the James Webb Telescope, which could reduce noise and provide a more accurate picture of the centre of our galaxy. The lead author of the study, Yusef-Zadeh, noted that dealing with noise is crucial with such faint flares and expressed hope that longer observations will unveil features previously unseen and determine whether the bursts are recurring or entirely random.
