An international team, including U.S. researchers, reports it has definitively measured the spin rate of a super-massive black hole for the first time. Based on data from two X-ray space observatories, NASA's Nuclear Spectroscopic Telescope Array and the European Space Agency's XMM-Newton, the findings will lead to a better understanding of how black holes and galaxies evolve, the researchers said. "We can trace matter as it swirls into a black hole using X-rays emitted from regions very close to the black hole," Fiona Harrison, NuSTAR principal investigator at the California Institute of Technology in Pasadena, Calif., said. "The radiation we see is warped and distorted by the motions of particles, and by the black hole's incredibly strong gravity." Astronomers are interested in measuring the spin rates of black holes in the hearts of galaxies because the formation of super-massive black holes is thought to mirror the formation of the galaxy itself. "We know that black holes have a strong link to their host galaxy," research team member Bill Craig, an astrophysicist at Lawrence Livermore National Laboratory, said in an LLNL release Wednesday. "Measuring the spin, one of the few things we can directly measure from a black hole, will give us clues to understanding this fundamental relationship." The researchers said their results showed the black hole is spinning close to the maximal rate allowed by Albert Einstein's theory of gravity.