In its center is a shadow, where the black hole’s intense gravitational pull prevents even light from escaping. Fortunately, says Galison, “we live in a golden age of observational astronomy.” Data gathered from eight telescopes at six separate sites around the globe, all part of the Event Horizon Telescope (EHT), were combined to create the image, which shows a donut-shaped ring of dense, hot gas, emitting energy. For an astronomer to see a star being pulled around like that is amazing.”ĭespite its relative proximity to Earth, creating the image of Sagittarius A* that was published today required a telescope the size of the planet. Many planets orbit the sun slower than that. In fact, two astronomers, Reinhard Genzel and Andrea Ghez, who won the 2020 Nobel Prize in physics, “were able to see these stars going around incredibly fast,” says Galison, “on 15-year orbits. Sagittarius A*, though just 15 million miles across, is close enough to Earth that astronomers can actually see stars orbiting around it. Big compared to Earth, but because it’s 55 million light-years away, it’s like seeing a grain of sand in Los Angeles from Boston.” (In the same way, the moon appears to observers on Earth to be about the same size as the far more massive sun, as anyone who has experienced a full eclipse has seen.) “M87* is 20 billion miles across,” Galison says, “about three times the size of our solar system. Though smaller than M87*, the black hole at the center of the Milky Way Galaxy occupies about the same amount of the sky because it is much closer to Earth, explains Pellegrino University Professor Peter Galison. Sagittarius A*, a supermassive black hole, is just 25,000 light-years (more than 147 trillion miles) from Earth, much closer than Messier 87* (M87*), the first black hole whose image, when published in April 2019, made headlines around the world. More than 300 scientists worldwide, working collaboratively, have created an extraordinary image of the black hole at the center of the Milky Way Galaxy.
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