Free Astronomy Magazine March-April 2022

39 MARCH-APRIL 2022 ASTRO PUBLISHING vations from a variety of telescopes that suggest the black hole burps out mini-jets every time it swallows something hefty, like a gas cloud. His multinational team’s research has been published in The Astro- physical Journal . In 2013 evidence for a stubby south- ern jet near the black hole came from X-rays detected by NASA’s Chandra X-ray Observatory and ra- dio waves detected by the Jansky Very Large Array telescope in So- corro, New Mexico. This jet too ap- pears to be plowing into gas near the black hole. Cecil was curious if there was a northern counter-jet as well. He first looked at archival spectra of such molecules as methyl alcohol and carbon monosulfide from the ALMA Observatory in Chile (Atacama Large Millimeter/submil- limeter Array), which uses millime- ter wavelengths to peer through the veils of dust between us and the galactic core. ALMA reveals an ex- panding, narrow linear feature in molecular gas that can be traced for 15 light-years back towards the black hole. By connecting the dots, Cecil next found in Hubble infrared- wavelength images a glowing, in- flating bubble of hot gas that aligns to the jet at a distance of at least 35 light-years from the black hole. His team suggests that the black hole jet has plowed into it, inflating the bubble. These two residual effects of the fading jet are the only visual evidence of it impacting molecular gas. As it blows through the gas the jet hits material and bends along multiple streams. “The streams per- colate out of the Milky Way’s dense gas disk,” said co-author Alex Wag- ner of Tsukuba University in Japan. “The jet diverges from a pencil beam into tendrils, like that of an octopus.” This outflow creates a se- ries of expanding bubbles that ex- tend out to at least 500 light-years. This larger “soap bubble” structure T his is a composite view of X-rays, molecular gas, and warm ionized gas near the galactic center. The graphic of a translucent, vertical white fan is added to show the suggested axis of a mini-jet from the supermassive black hole at the galaxy’s heart. The orange-colored features are of glowing hydrogen gas. One such feature, at the top tip of the jet is interpreted as a hydrogen cloud that has been hit by the outflowing jet. The jet scatters off the cloud into tendrils that flow northward. Farther down near the black hole are X-ray observations of super- heated gas colored blue and molecular gas in green. These data are evidence that the black hole occasionally accretes stars or gas clouds, and ejects some of the su- perheated material along its spin axis. [NASA, ESA, Gerald Cecil (UNC-Chapel Hill)] has been mapped at various wave- lengths by other telescopes. Wagner and Cecil next ran supercomputer models of jet outflows in a simu- lated Milky Way disk, which repro- duced the observations. “Like in archeology, you dig and dig to find older and older artifacts until you come upon remnants of a grand civ- ilization,” said Cecil.