Black hole jets accelerate heavy elements

Ars Technica : As a star orbits a black hole, it is stripped of matter that forms an accretion disk around the black hole. But not all of the matter is absorbed—much is accelerated and ejected into high-energy jets perpendicular to the disk. Previous measurements have shown that the matter in the jets is traveling at high fractions of the speed of light. Astronomers assumed that the matter was mostly made up of electrons because they are very light, but may also include heavier protons. María Díaz Trigo of the European Southern Observatory and her colleagues have now found that those jets also include very heavy particles, which require much more energy to accelerate to high speeds. Díaz Trigo’s team examined a flare of x-ray and radio emissions from 4U 1630-47, a binary star whose compact member is believed to be a black hole. The emissions displayed a spectrum that revealed the presence of two iron ions, which are 100 000 times as massive as electrons. And the ions were moving at two-thirds the speed of light. Because 4U 1630-47 is a standard-looking black hole binary system, it is likely that other such systems also accelerate heavy elements. The discovery could be important to our understanding black hole behavior.