Free Astronomy Magazine March-April 2022

MARCH-APRIL 2022 Mini-jet discovered near Sagittarius A* by NASA/ESA Ray Villard T he nearby barred-spiral galaxy NGC 1068 serves as a proxy for helping as- tronomers understand the fireworks taking place at the center of our Milky Way galaxy, driven by eruptions from a supermassive black hole. Because we live inside the Milky Way, much of our view of the galaxy’s center is blocked by intervening clouds of gas and dust. But, looking 47 million light-years away at NGC 1068 gives astronomers a birds-eye view of similar black hole outbursts. The inset Hubble Space Telescope image resolves hydrogen clouds as small as 10 light-years across within 150 light-years of the core. The clouds are glowing be- cause they are caught in a “searchlight” of radiation beamed out of the galaxy’s black hole, which is larger and more active than the black hole in the heart of our galaxy. [NASA, ESA, Alex Filippenko (UC Berkeley), William Sparks (STScI), Luis C. Ho (KIAA-PKU), Matthew A Malkan (UCLA), Alessandro Capetti (STScI)] O ur Milky Way’s central black hole has a leak. This super- massive black hole (Sagittar- ius A*) looks like it still has the vestiges of a blowtorch-like jet dat- ing back several thousand years. NASA’s Hubble Space Telescope has not photographed the phantom jet but has helped find circumstantial ev- idence that it is still pushing feebly into a huge hydrogen cloud and then splattering, like the narrow stream from a hose aimed into a pile of sand. This is further evidence that the black hole, with a mass of 4.1 million Suns, is not a sleeping monster but period- ically hiccups as stars and gas clouds fall into it. Black holes draw some material into a swirling, orbiting ac- cretion disk where some of the in- falling material is swept up into outflowing jets that are collimated by the black hole’s powerful mag- netic fields. The narrow “searchlight beams” are accompanied by a flood of deadly ionizing radiation. “The central black hole is dynamically variable and is currently powered down,” said Gerald Cecil of the Uni- versity of North Carolina in Chapel Hill. Cecil pieced together, like a jig- saw puzzle, multiwavelength obser-