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For the First Time, Astronomers Capture Image of a Black Hole’s Shadow and a Strong Jet

This is the first image of Sgr A*, the supermassive black hole at the centre of our galaxy, with an added black background to fit wider screens. It’s the first direct visual evidence of the presence of this black hole. It was captured by the Event Horizon Telescope (EHT), an array which linked together eight existing radio observatories across the planet to form a single “Earth-sized” virtual telescope. The telescope is named after the event horizon, the boundary of the black hole beyond which no light can escape.   Although we cannot see the event horizon itself, because it cannot emit light, glowing gas orbiting around the black hole reveals a telltale signature: a dark central region (called a shadow) surrounded by a bright ring-like structure. The new view captures light bent by the powerful gravity of the black hole, which is four million times more massive than our Sun. The image of the Sgr A* black hole is an average of the different images the EHT Collaboration has extracted from its 2017 observations.  In addition to other facilities, the EHT network of radio observatories that made this image possible includes the Atacama Large Millimeter/submillimeter Array (ALMA) and the Atacama Pathfinder EXperiment (APEX) in the Atacama Desert in Chile, co-owned and co-operated by ESO is a partner on behalf of its member states in Europe.

Astronomers have captured the first image of a black hole’s shadow alongside a powerful jet. The panoramic picture of the black hole and its jet was taken at a new wavelength, revealing more about the physical processes occurring near the black hole. The image shows that the ring that was previously seen is becoming larger and thicker at a 3.5 mm observing wavelength, indicating that the material falling into the black hole produces additional emission that is now observed in the new image. The diameter of the ring measured by the Global Millimeter VLBI Array (GMVA) is 64 microarcseconds, which corresponds to the size of a small (5-inch/13-cm) selfie ring light as seen by an astronaut on the Moon looking back at Earth. The light from M87 is produced by the interplay between highly energetic electrons and magnetic fields, a phenomenon called synchrotron radiation. The new observations, at a wavelength of 3.5 mm, reveal more details about the location and energy of these electrons. They also tell us something about the nature of the black hole itself: it is not very hungry. It consumes matter at a low rate, converting only a small fraction of it into radiation. The quest to learn more about Messier 87 is not over, as further observations and a fleet of powerful telescopes continue to unlock its secrets.

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