Three years after capturing the first image of a supermassive black hole in a galaxy 55 million light years away, astronomers have managed to "photograph" the gaping maw of the smaller but much closer black hole quietly lurking at the core of the Milky Way, researchers announced Thursday. "We are peering into a new environment, the curved spacetime near a supermassive black hole," said Michael Johnson, a researcher at the Harvard-Smithsonian Center for Astrophysics. "And it is teeming with activity, always burbling with turbulent energy and occasionally erupting into bright flares of emission." The black hole at the center of the Milky Way, known as Sagittarius A*, or Sgr A*. EHT Collaboration The 2019 target was a mind boggling black hole at the core of M-87, a giant elliptical galaxy in the constellation Virgo, a hole with the mass of 6.5 billion suns. Its enormous gravity pulls surrounding material into a disc, accelerating it to nearly the speed of light and heating it to extreme temperatures, resulting in torrents of radiation that can be seen from Earth. The black hole at the center of the Milky Way, known as Sagittarius A*, or Sgr A* for short (pronounced Sag A-star), is much closer, about 26,000 light years from Earth, but it is much smaller. The 6.5 billion solar masses making up the M-87 black hole would fill the entire solar system. The 4 million solar masses of Sgr A* would fit inside the orbit of Mercury. A combination of photos comparing the black hole at the center of the Milky Way, known as Sagittarius A*, or Sgr A* (left) and the one at the core of M-87 (right). EHT Collaboration Now, after years of careful data collection using eight radio telescope electronically combined and synchronized with atomic clocks to form a virtual dish the size of planet Earth, collaborators with the Event Horizon Telescope project unveiled the long-sought-after image of Sgr A*. It was a feat roughly equivalent to a photographing a single grain of salt in New York City using a camera in Los Angeles. Sgr A* has been the focus of "intense astronomical studies for decades," said Feryal Özel, a theoretical astrophysicist at the University of Arizona and an EHT team leader. "Observations of stars orbiting around it revealed the presence of an object that is very massive, 4 million times the mass of our sun, but also very faint. "Until now, we didn't have the direct picture confirming that Sgr A* was indeed a black hole," she said. "Today, the Event Horizon Telescope is delighted to share with you the first direct image of the gentle giant in the center of our galaxy." The image, based on multiple observations using a variety of algorithms to tease out subtle details, "shows a bright ring surrounding the darkness, the telltale sign of the shadow of the black hole," Özel said. "Light escaping from the hot gas swirling around the black hole appears to us as the bright ring. Light that is too close to the black hole, close enough to be swallowed by it, eventually crosses its horizon and leaves behind just the dark void in the center." By definition, black holes cannot be directly observed because nothing, not even light, can escape the crushing inward force of their titanic gravity. But their presence can be indirectly detected by observing the effects of that gravity on the trajectories of nearby stars and by the radiation emitted across the electromagnetic spectrum by material heated to extreme temperatures as it's sucked into a rapidly rotating "accretion disk" and then into the hole itself. The motions of stars in the dust-shrouded core of the Milky Way near Sgr A* have been closely monitored for the past two decades, allowing astronomers to calculate the mass of the invisible body warping their trajectories. An animation shows how the gravity of the Milky Way's central black hole warps the trajectories of nearby stars. Analyzing those trajectories, astronomers conclude the unseen black hole has the mass of 4 million suns. Keck/UCLA Galactic Center Group The 2020 Nobel Prize went to three researchers whose pioneering observations and analysis all but confirmed the presence of a supermassive black hole. The Event Horizon Telescope captured the first actual image of the massive object. That image shows Sgr A*'s dark central core — the shadow of its "event horizon" — surrounded by a lopsided ring of light emitted by particles racing around the hole at nearly the speed of light. The event horizon is the invisible boundary between a black hole and the rest of the universe, a zone where nothing, not even light, can escape the hole's gravitational clutches. Gas, dust, wayward stars and the light they emit, anything crossing that invisible line vanishes from the known universe. The EHT image of Sgr A* is similar in appearance to the historic image of M-87's huge black hole and closely resembles what astronomers expected based on computer simulations running the equations of Einstein's general theory of re . . . read the full article here.