Mysterious Cygnus Bubble may trace back to microquasar, astronomers suggest

A new study suggests that the mysterious Cygnus Bubble, a cloud of ultra-high-energy gamma rays, may be linked to a microquasar rather than a star-forming region. The research, published in The Astrophysical Journal Letters, proposes that the bubble's highest-energy emission is produced by the microquasar Cygnus X-3, which is much farther away than previously thought. The study found that Cygnus X-3 accelerates particles to at least 30 PeV in sync with its 4.8-hour orbit, providing direct evidence of extreme acceleration occurring within the binary system. The researchers built a model that simulated the process, showing that Cygnus X-3 would need to funnel only 1% to 3% of its power into particle acceleration and that the particle-spreading rate needed to match the observed data. If confirmed, the Cygnus Bubble would be the first known example of a gamma-ray halo powered by a microquasar. The study highlights a unique case where astronomers can observe both the accelerator and the halo of particles it has created. Current telescopes lack the resolution to distinguish the Cygnus X-3 signal from the star cluster's contribution, a distinction that future observatories should be better equipped to resolve. The researchers conclude that next-generation instruments like the Cherenkov Telescope Array will be sensitive enough to test whether Cygnus X-3 is indeed the source.

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