NASA's NuSTAR, has helped to show that the spin rates of black holes can be measured conclusively. The solid lines show two theoretical models that explain low-energy X-ray emission seen previously from the spiral galaxy NGC 1365 by XMM-Newton.
Scientists measure the spin rates of supermassive black holes by spreading the X-ray light into different colors. The light comes from accretion disks that swirl around black holes, as shown in both of the artist's concepts.
How to Measure the Spin of a Black Hole (Artist's Concept)
Black holes are tremendous objects whose immense gravity can distort and twist space-time, the fabric that shapes our universe as this chart from NASA's NuSTAR and ESA's XMM-Newton telescope illustrates.