Though scientists learn more about them all the time, black holes are one of the most mysterious phenomena in the universe. They’re certainly difficult for most people to understand on an intuitive level, the way we can grasp the scale of the Earth, for example.
Black holes are stars that have burnt out and collapsed in on themselves. They become so incredibly dense that their gravitational field is strong enough to stop even light from escaping them as they bend space and time around their edges.
Now, some astronomers are researching a phenomenon in black holes they’re calling a “heartbeat,” a regular pulse of X-ray activity. The phenomenon occurs in black holes that exist in a binary system, meaning they orbit another star. Technically speaking, both bodies orbit each other.
The black hole’s gravitational well pulls in gasses from the still-burning star. The gas then compresses, which raises its temperature, and the black hole sends out huge amounts of X-ray radiation. This is actually how astronomers first discovered black holes, as the stars themselves are quite literally black and unable to be seen optically.
The timescales are enormous. The black hole can feed on gas from a companion star for millions of years before it sort of accelerates and takes in a much bigger quantity all at once (or, at what appears to humans as “all at once”). This causes a flare visible to X-ray sensitive equipment. But the flare isn’t constant; researchers have detected a regular, pulsing variability to the flare they call a “heartbeat flare” because it looks like the signal of a human heart measured by an EKG machine.
An astronomy team at the Chinese Academy of Sciences in Beijing are working on a recent and large heartbeat flare and they’re describing their findings in a paper that’s still in preprint. When finished it will appear in The Astrophysical Journal.
The star they’re looking at is a black hole with the cumbersome designation IGR J17091-3624. It is 28,000 light-years from Earth. That means that anything we can see from that location is light that left the region 28,000 years ago; it is literally to look into the past.
The team analyzed the pulses and believes the regular heartbeat has something to do with the behavior of matter that surrounds the black hole. Black holes form a large, flat disc of material around them called an accretion disc. Researchers believe that at a certain point, the disc gives up a large amount of matter at once that falls into the black hole, creating the heartbeat pulse.
