About 15,000 light-years away, an active black hole periodically appears to illuminate another unremarkable cloud of gas with gamma rays. But there is a catch. The gas cloud is about 100 light-years from the black hole – and just how the cloud pulsates with it in time is a mystery.
Astrophysicists believe it is unlikely that the pulsations are generated directly by the plasma jets emitted by active black holes. But it is possible that the black hole somehow blows cosmic rays in a way that illuminates the gas cloud.
“This result challenges obvious interpretations and is unexpected from previously published theoretical models,” said astrophysicist Jian Li of the Deutsches Elektronen-Synchrotron in Germany.
“It offers us the opportunity to discover the particle transport of SS 433 and to investigate the structure of the magnetic field in its vicinity.”
SS 433 is the black hole system, of a kind known as mikroquasar. It consists, apparently, of the black hole – a relatively carpeted fella, which weighs 10 to 20 times the mass of the Sun. The binary companion is a superior main sequence, about 30 times the mass of the Sun.
The two are trapped in a very narrow orbit, just a hair over 13 days, leaving the black hole a constant stream of material from his star companion siphoning, flushing around like water around a sewer. While doing so, the material shines, just like a mini version of a quasar.
But not all material is slurped. Some of it is channeled away from the inner edge of the action disk around the outside of the black hole – we are not entirely sure how, but scientists think it runs along magnetic field lines.
This material is then emitted from – presumably – the pulse of the black hole in plasma jets which can approach significant percentages of the speed of light.
In addition, the black hole in SS 433 wobbles, like a spinning top, on its rotate. This wobble is called rotational procession, and it means that the jets, instead of in a straight line, shoot into space, as seen in the video below of another previous microquasar, V404 Cygni.
By observing SS 433 for a decade, Li and his team were able to determine that the progression of the black hole has a periodicity of just over 162 days, with the jet losing its spiral shape and relaxing a cone after a few cycles. And the gas cloud pulses with gamma radiation on the same time scales.
This may seem like an open-ended business, but it’s a big problem. The cloud does not really lie within the extrapolated jet cone.
“Finding such an untimely connection via timing, about 100 light-years away from the micro-quasar, not even along the direction of the jets is as unexpected as [it is] great, “said Li. But how the black hole can support the heartbeat of the gas cloud is unclear to us. “
It may be unclear, but that does not mean there are no potential explanations. It is possible that cosmic rays – high-energy protons that travel almost at the speed of light – are produced through the black hole, either at the ends of the jets, or from the equator.
At the end of the jets, as near the black hole, the subatomic particles of cosmic rays could be sent out to the cloud. When struck, the impact could then produce gamma rays, as described in a 2005 theoretical paper.
Or it is possible that the cosmic rays originate from the edge of the action disk.
“Energetics could have the outflow of the disk as powerful as that of the jets and is thought to be in solidarity with the rest of the system,” explained astrophysicist Diego Torres of the Institute of Space Sciences in Spain.
These cosmic rays would have to be emitted at a sufficient rate to produce the observed emma of ray ray. This, the researchers said, is difficult to reconcile with our current understanding of the source environment.
So there is a lot more work to be done to understand the system – and just how it illuminates a gas cloud 100 light-years away.
“SS 433 continues to amaze observers at all frequencies and theorists alike,” the researchers wrote, “and is sure to provide a test bed for our ideas of cosmic ray production and propagation in the vicinity of microquasars for years to come.”
The study was published in Natural Astronomy.
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