PerspectiveAstronomy

A Tale of Two Jets

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Science  20 Aug 2010:
Vol. 329, Issue 5994, pp. 908-909
DOI: 10.1126/science.1194182

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Summary

One of the most astounding astrophysical phenomena is the existence of highly collimated jets of highly energetic particles found emanating from localized regions in the sky. These jets are ubiquitous, having been observed in the radio and x-ray spectrum at the center of galaxies, gamma-ray bursts, and quasars. Although their precise generation mechanism remains unknown, these jets are believed to be powered by black holes. Black holes do not shine in isolation, because their gravitational field is so strong that not even light can escape their pull. However, they are usually accompanied by rotating disks of gas and dust matter (called accretion disks) and can form strongly collimated emissions through a variety of mechanisms. On page 927 of this issue, Palenzuela et al. (1) numerically model the merger of two black holes surrounded by an accretion disk that orbits around both of them (forming a circumbinary) and anchors a magnetic field perpendicular to the orbital plane. Each black hole generates a jet, produced by the twisting of the magnetic field lines as they lose energy and spiral toward each other (inspiral), even though the black holes are not spinning. Their simulations show the formation of two jets and their transition to a single jet as the black holes merge.