Black-hole Emissions Untangled

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<b>Black-hole Emissions Untangled</b><br /><br />LINK<br /><br />Black holes spew out X-rays in two distinct ways, astronomers have shown. Being able to separate the components of X-ray signals should help astronomers understand how black holes work.<br /><br />Scientists had predicted that the jets and disk of matter that surround a black hole would emit different patterns of radiation. But this is the first time that observations of the two types of X-rays have been teased apart. <br /><br />Black holes are enigmatic beasts. By definition, they cannot be observed directly, as even light cannot escape from their gravitational hold. But astronomers can observe the intense radiation emitted by material as it is sucked into the void. X-rays are the brightest component of that radiation, emitted by matter passing close to the 'event horizon', the point of no return as you approach a black hole.<br /><br />As dust and gas is sucked into a black hole, it forms a doughnut-shaped disk that swirls around the centre before falling in. Friction heats up the ions and electrons in the disk to around 10,000 °C, generating X-rays in the process.<br /><br />Although most of the material is ultimately dragged into the black hole, some of it is spat out by the hole's strong magnetic field instead, creating two tight jets pointing in opposite directions. In these jets, electrons spiral through the magnetic field at close to the speed of light, generating X-rays in the same way that electrons moving back and forth in a radio transmitter generate radio waves.<br /><br />Astronomers predict that the disk should produce lower energy X-rays than the jets. But no one had ever been able to show for sure which of the X-rays picked up by telescopes came from which source. "Nobody has been able to see them both working together until now," says Giorgio Palumbo, an astrophysicist from the University of Bologna, Italy.<br />