Study suggests black hole jets get their power from spin

(Phys.org) —A team of space scientists working in Italy has found more evidence that suggests the energy needed to emit jets from supermassive black holes comes from the spin of the black hole itself. In their paper published in the journal Nature, the team describes how their survey of data from NASA’s Fermi Gamma-ray Space Telescope allowed for comparing two types of emissions from the black holes, which showed a correlation.

more…

Of course.

I’ve done a bit of computing of stellar jets in young stars, not too different to black hole jets. A problem has been that every single mathematical model proposed so far fails to explain why the jet is so narrow – it should spread out more.

The mathematical model I was working with starts with material in tight orbit around the equatorial plane of the star (or black hole). When it gets closer than a critical radius, hydro-magnetic forces due to the circulation of ions in orbit around the star cause the orbit to go unstable, flinging it out perpendicular to the orbit along the axis of the star (or black hole). Thereafter there are two competing hypotheses. In the one I was working on, hydrodynamic effects (basically just conservation of mass, momentum and angular momentum) in unionised material act to confine the out-flowing material into a polar jet. In the other hypothesis out-flowing ionised material follows the magnetic field lines of the star (or black hole). I personally think the second hypothesis is wrong. Neither hypothesis explains the narrowness of the observed jets, but mine does a better job of it.