New study sheds light on source of mysterious black hole flares
Observations carried out by NASA's Swift and Nuclear Spectroscopic Telescope Array (NuSTAR) space telescopes may have located the source of intense X-ray bursts emitted by supermassive black holes. According to NASA, the phenomenon can be attributed to a component of a black hole known as a corona.
The black hole around which the flare was discovered, known as Markarian 335 (Mrk 335), sits roughly 324 million light-years distant from Earth in the Pegasus constellation. Whilst black holes give off no light of their own, telescopes are able to detect light created by gas drawn in by the intense gravity emanating from bodies such as Mrk 335. As the gas approaches the event horizon, it becomes superheated, causing it to shine brightly.
Telescopes are also able to detect light created by a black hole's corona, a structure of high energy particles that is documented to give off light in the X-ray spectrum. Currently, there are two theories regarding the structure of a corona.
The first, known as the "lamppost" model, asserts that the corona is a compact, lightbulb-like source of light positioned above and below the singularity along its rotational axis. The second possibility contends that the corona takes the form of a diffuse cloud surrounding the black hole, or as two flatter sections that shroud the singularity. This is known as the "sandwich" model.
In September 2014, NASA's Swift telescope was lucky enough to catch an X-ray flare event in action at Mrk 335, and the astronomers quickly re tasked the NuSTAR platform for follow up observations. By observing X-ray light, it was discovered that the source of the flare was the corona being ejected from the black hole.
Moving at roughly 20 percent the speed of light, the corona was observed forming at the base of the flare prior to being discharged into space. As a side effect of the phenomenon, light emitted from the corona was amplified via an effect known as relativistic Doppler boosting.
"This is the first time we have been able to link the launching of the corona to a flare," explains lead author of a new paper on the results Dan Wilkins, of Saint Mary's University in Halifax, Canada. "This will help us understand how supermassive black holes power some of the brightest objects in the universe."
The findings support what is known as the "lamppost" model, but many key aspects of coronas are still a total mystery, such as how they form, or the mechanism by which they trigger the flares.