Known as J221951, this cosmic marvel is among the most luminous transients - astrophysical objects that drastically change their brightness over short periods - ever observed
In what is an incredible find, astronomers say they have witnessed the energetic ignition of a black hole.
In an unprecedented celestial discovery, British astronomers have reported one of the most dramatic black hole “ignitions” ever recorded, says the Royal Astronomical Society (RAS). Known as J221951, this cosmic marvel is among the most luminous transients – astrophysical objects that drastically change their brightness over short periods – ever observed.
Astronomers witness the energetic ignition of a black hole
Dr. Samantha Oates and her team from the University of Birmingham stumbled upon J221951 in September 2019. They were scanning for electromagnetic light originating from a gravitational wave event using the Ultraviolet and Optical Telescope at the Neil Gehrels Swift Observatory. They aimed to locate a kilonova, a telltale sign of a neutron star merging with another neutron star or black hole.
Kilonovas generally appear blue, then slowly fade and turn redder over several days. But instead, they discovered something even more peculiar: J221951. This transient exhibited a blue hue but didn’t fade or shift color as rapidly as a typical kilonova.
Tracing the Transient’s Nature
To decipher the nature of J221951, several telescopes were employed, including NASA’s Swift/UVOT and Hubble Space Telescope, the South African Large Telescope, and ESO facilities such as the Very Large Telescope and the GROND instrument on the MPG/ESO 2.2-metre telescope at La Silla Observatory.
Light spectrum analysis of J221951 through the Hubble Space Telescope excluded its association with the gravitational wave event. Dr. Oates’ team ascertained that the source of J221951 lies approximately 10 billion light-years away, in stark contrast to the detected gravitational wave signal’s distance of less than 500 million light-years.
A Black Hole’s Dramatic Feast
J221951’s exceptional brightness at such a vast distance classifies it as one of the most luminous transients ever detected. Indications suggest that this astonishing illumination resulted from a supermassive black hole voraciously consuming surrounding material.
Researchers observed a red galaxy at the J221951’s location before its detection. The location corresponds with a galaxy’s center, where a massive black hole would typically reside. Approximately 10 months prior to the initial detection, the object started to brighten suddenly, implying the black hole swiftly started feeding after a dormant period.
The ultraviolet spectrum displays absorption traits consistent with material expelled by a massive energy release. Coupled with its incredible luminosity, this ranks among the most dramatic black hole “ignitions” ever witnessed.
Possible Causes of the Extreme Feeding Event
The team proposes two possible mechanisms that could explain this extreme feeding event from a supermassive black hole. One possibility is a tidal disruption event – the destruction of a star as it drifts close to the supermassive black hole at its galaxy’s center. Alternatively, an active galactic nucleus may have transitioned from inactive to active, triggering J221951 as a sign of an inactive black hole at the host galaxy’s center beginning to devour material from an accretion disk.
These findings were presented at the National Astronomy Meeting in Cardiff and will be published in the Monthly Notices of the Royal Astronomical Society.
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