The Nuclear Spectroscopic Telescope Array was launched in June of 2012, joining the Advanced X-Ray Astrophysics Facility (the Chandra mission) and the European Space Agency’s X-Ray Multi-Mirror Mission – Newton observatory. The NuSTAR telescope mission receives high-energy X-Rays in the range of 3 to 79 keV, seeking to study the history of supermassive black holes and the high-velocity particle acceleration around the accretion disks of those black holes.
NuSTAR and the XMM-Newton observatories successfully measured the spin rate of the supermassive black hole NGC 1365, 56 light-years distant. The statistical analysis and observational results have been published by Risaliti, Harrison, Madsen, et al. as a Letter in the February 28th edition of the Nature scientific journal. NGC 1365 is a 2-million solar-mass black hole that is spinning at close to the rotational limit as predicted by Einstein’s General Theory of Relativity.
The history of formation of a black hole can be determined by its eating habits. A slow-eating black hole results in slow growth and an accretion disk that is further from its subspace origin. A fast-eating black hole will have an accretion disk with an inner edge that is held gravitationally closer to the singularity, and the increased gravitational flux at that distance causes an increase in the bending of X-Rays emanating from the matter that is being pulled across the accretion disk. This bending is detectable, for elements such as iron, in the redshift of the X-Rays.
A complication in the detection of X-Ray redshift has been that the radiation must travel through the gas that surrounds the accretion disk, which causes an absorption spectrum to form and alters the detectable accuracy of the rotation rate of the black hole. Because the NuSTAR telescope has a detection capability into the region of 80 keV, it was able to determine the difference between the gas absorption and redshifted gravitational effects on the iron atoms. As the absorption effects of gas clouds can be excluded as a cause of the observed redshift bending in the iron signatures, the data collected for other black hole spin rates by NuSTAR and XMM-Newton can be substantiated solely on the basis of the gravitational effects from the singularity.
Our guest speaker, Will Marchant, will present an overview of the NuSTAR mission and these latest results.