ANN ARBOR—Data from the University of Michigan Radio Observatory at Peach Mountain in Dexter, Mich., helped scientists catch a supermassive black hole in a distant galaxy in the act of spurting energy into a jet of electrons and magnetic fields on four distinct occasions in the past three years, a celestial take on a Yellowstone geyser.This quasar-like “active” galaxy, called 3C120, is essentially a scaled-up model of the so-called microquasars within our Milky Way galaxy. These microquasars are smaller black holes as massive as about 10 suns in a solar system with a normal star. Scientists can now use this close-up view of microquasars to develop working models of the most massive and powerful black holes in the universe.The results—published in the June 6 issue of Nature and announced in early June at the American Astronomical Society meeting in Albuquerque, N.M.—are the fruit of a three-year monitoring campaign utilizing the Very Long Baseline Array (VLBA), a continent-wide radio-telescope system operated by the National Radio Astronomy Observatory (NRAO), the National Aeronautic and Space Administration‘s Rossi X-ray Timing Explorer, the Metsahovi Radio Observatory (Finland), and the University of Michigan’s 26-meter radio telescope. The 26-meter University of Michigan paraboloid is located at Peach Mountain, on North Territorial Road in Dexter. It operates nearly 24 hours per day using an automatic computer control system. The on-site supervisor is George E. Latimer. The Observatory is open to the public annually on the third Sunday in September, from 2 to 4:30 pm.] “The Peach Mountain observatory is the only radio instrument in the United States dedicated to observations of Active Galactic Nuclei with sufficient temporal resolution to follow the variations in luminosity that are associated with changes in the jet outflows. Galaxy 3C120 is one of four sources under investigation using this unique combination of instruments,” said U-M research scientist Margo Aller.Aller and her husband, Hugh, a professor in the Department of Astronomy, have been conducting studies of variability in extragalactic objects at the facility for nearly three decades. Peach Mountain is the only radio instrument in the United States dedicated to this type of study, and the only instrument of any type in the United States dedicated to this study on a full-time basis. The other instruments used in the study allocate only a fraction of their time to projects of this type.”This is first direct, observational evidence of what we had suspected: the jets in active galaxies are powered by disks of hot gas orbiting around supermassive black holes,” said Alan Marscher of the Institute for Astrophysical Research at Boston University, leader of the international team of astronomers. (Refer to the end of this release for the team member list.)Active galaxies are distant celestial objects with exceedingly bright cores, often radiating with the brilliance of thousands of ordinary galaxies, fueled by the gravity of a central million- to billion-solar-mass black hole pulling in copious amounts of interstellar gas.Marscher and his colleagues have established the first direct observational link between a supermassive black hole and its jet. The source is an active galaxy named 3C120 about 450 million light years from Earth. This link has been observed in microquasars, several of which are scattered across the Milky Way galaxy, but never before in active galaxies, because the scale (distance and time) is so much greater.The jets in galaxy 3C120 are streams of particles shooting away perpendicular to the plane of a black hole’s accretion disk, moving at 98 percent of the speed of light. In microquasars, radio-emitting features become visible in a jet shortly after X-rays from the accretion disk get dimmer—as if the accretion disk suddenly flushes into the black hole and disappears, fueling the jet. These radio “blobs” then appear to move at faster than light speeds, an illusion caused by their ultra-high speeds.Now the team of scientists sees this same phenomenon in 3C120. Roughly every 10 months, the X-ray-emitting accretion disk around its supermassive black hole becomes suddenly dim, and a month later the telltale bright spot of radio emission appears in the jet. Over a three-year period, the team observed a series of radio blobs floating along the particle jet like smoke puffs, each time following a dip in the brightness of X-rays from the accretion disk.”What we are likely seeing is the inner part of the accretion disk becoming unstable and suddenly plunging into the black hole,” said Marscher. “We detect a ‘dip’ in the X-ray flux as the hot gas in the disk disappears after it passes the event horizon. The remainder of the disk is channeled into the jets, which we see as a knot of radio emission bubbling away from the black hole. Slowly the accretion disk fills with more interstellar gas until about 10 months later, when something disturbs the accretion disk orbit, and the whole thing flushes and blows again.”Joining Aller and Marscher on this observation and analysis are Svetlana Jorstad of Boston University; Jose-Luis Gomez of the Astrophysical Institute of Andalucia in Granada, Spain; Harri Terasranta of the Helsinki University of Technology; Matthew Lister of NRAO; and Alastair Stirling of the University of Central Lancashire, England.The VLBA is a continent-wide radio-telescope system, with one telescope on Hawaii, another on St. Croix in the Caribbean, and eight others in the continental United States. The National Radio Astronomy Observatory is a facility of the National Science Foundation, operated under cooperative agreement by Associated Universities, Inc. The Rossi Explorer, operated by NASA Goddard Space Flight Center in Greenbelt, Md., was launched in 1995 to study black holes, neutron stars and pulsars. The Metsahovi program in Kylmala, Finland, has used an 13.7-meter telescope to study variability at high frequencies since 1980. The 26-meter telescope at the University of Michigan Radio Observatory operated by the Department of Astronomy, was built in the late 1950s.Further information on this research is available at http://www.bu.edu/blazars/XR.html. Information on the University of Michigan Radio Observatory is available at http://www.astro.lsa.umich.edu/Obs/nonobs.html.