Astronomers have long been fascinated by the strange phenomenon of “heartbeat” black holes, which emit X-ray signals that resemble a human heartbeat. Now, new research may finally explain why these black holes exhibit this behavior.
Black holes can develop a “heartbeat” when they consume enormous amounts of gas in a binary system, where they share an orbit with another star. This process heats up the gas to incredibly high temperatures, emitting copious amounts of X-ray radiation.
In the midst of this feeding frenzy, which can last for thousands to millions of years, there can occasionally be a tremendous outburst, causing a sudden flare of X-rays. Researchers have studied many such flares over the years and noticed strange behavior, including a regular pulse of activity embedded within the flare event. These pulses are known as “heartbeat” flares.
Recently, a team of astronomers at the Key Laboratory of Particle Astrophysics in Beijing has studied the most recent heartbeat flare and described the process that may fuel it. They analyzed X-ray data taken with the Neutron Star Interior Composition Explorer (NICER) and Nuclear Spectroscopic Telescope Array (NuSTAR) in 2022.
The study revealed that these heartbeat-like signals are caused by interactions and instabilities within the material surrounding the black hole. When material falls into a black hole, it forms a thin, rapidly rotating disk around the event horizon. This creates a highly unstable situation as radiation from the disk competes with the gravitational pull of the black hole.
To trigger a heartbeat, the disk temporarily fragments, releasing an enormous amount of radiation that begins the pulse. The radiation then heats up the gas, which temporarily prevents it from falling in. Then the gas settles down before the process repeats itself, setting the stage for another heartbeat.
These heartbeat signals are incredibly rare, occurring only in two out of hundreds known black holes. However, researchers hope to study more of these events as they provide valuable insights into the relationships between black holes and their environments.
Source: https://www.space.com/why-some-black-holes-have-heartbeats