By Will Dunham
WASHINGTON (Reuters) – The James Webb Space Telescope, launched in 2021 and operational since 2022, is offering unprecedented views of the tumultuous events unfolding around the supermassive black hole at the heart of our Milky Way galaxy. Observations show a continuous flickering of light with intermittent bright flares as material is drawn towards the black hole due to its immense gravitational force.
Named Sagittarius A* (Sgr A*), the black hole’s surroundings have been observed as highly dynamic rather than stable. The telescope’s extended monitoring has allowed astronomers to identify patterns of activity in this region for the first time.
A swirling disk of gas, known as an accretion disk, emits a constant flickering of light, believed to originate from material in close proximity to the event horizon – the point of no return beyond which everything is pulled into the black hole. Occasional flares, ranging from one to three large bursts per day with smaller bursts in between, were also detected.
Astrophysicist Farhad Yusef-Zadeh of Northwestern University and study lead author explained, “The accretion disk is a chaotic area filled with turbulence, where gas is compressed and becomes more erratic as it nears the black hole under intense gravitational forces.” Study co-author, astrophysicist Howard Bushouse, compared the gas behavior to solar flares, where blobs of gas collide and are compressed by magnetic fields present within the disk.
While these bursts resemble solar flares in their mechanism, they occur in a different astrophysical setting at significantly higher energy levels. Black holes are incredibly dense with gravitational pull so strong that even light cannot escape, making direct observations challenging. The recent study focused on observing the material surrounding Sgr A*.
With a mass roughly 4 million times that of the sun, Sgr A* is situated about 26,000 light-years away from Earth. Most galaxies harbor a supermassive black hole at their core, with Sgr A* being less active compared to black holes in other galaxies, existing in a relatively calm state.
The new findings are based on approximately 48 hours of continuous observation of Sgr A* by the Webb telescope over a year, providing valuable insights into the interactions between black holes and their surroundings. Yusef-Zadeh noted that around 90% of the accretion disk’s material falls into the black hole, with the remainder being expelled into space.
The accretion disk seems to consist of material collected from nearby stars’ stellar winds, indicating gas blown off these stars’ surfaces that is then captured by the black hole.
The researchers noted that the object was pulled in by the gravitational force of Sgr A* rather than being torn apart by a star that came too close. Prior to this discovery, astronomers were constrained to short observation periods using ground-based telescopes or brief windows of observation with the Hubble Space Telescope. This limited their ability to construct a comprehensive understanding. The James Webb Space Telescope, equipped with the advanced sensitivity of its Near-Infrared Camera (NIRCam), facilitated observations at two distinct infrared wavelengths. According to the researchers, Sgr A* has long been observed to exhibit bright flares across various wavelengths, including radio, infrared, optical, and X-rays. Previous observations, whether conducted from ground-based or space-based telescopes, were hampered by limited observation durations or lacked the necessary sensitivity to detect all but the most intense flares, as explained by Bushouse.
