Functioning as one Earth-sized telescope, the network can resolve objects just one-ten thousandth the angular size of what Hubble can see. In the end, six observatories in Mexico, Hawaii, Arizona, Chile, and Spain aimed their eyes into sky and stared at M87, which is the biggest galaxy in the center of the Virgo cluster. To resolve these supermassive black holes-which are tiny compared to their surrounding galaxies-the consortium needed to harness the power of radio telescopes all over the planet. Photograph courtesy NASA and the Hubble Heritage Team (STScI/AURA) With its relatively high brightness magnitude and at a distance of 28 million light-years from Earth, Messier 104, as Sombrero is more formally known, is easily viewed through a small telescope. Among the most memorable is this edge-on mosaic of the Sombrero galaxy. Over its lifetime, NASA's Hubble Space Telescope has captured many stunning images. When separate dishes simultaneously observe the same target, scientists can collate the observations and “see” an object as though they’re using one giant dish that spans the distance between those telescopes. Rather than being a single snapshot, like the many spectacular photos taken by the Hubble Space Telescope, the EHT‘s image is the product of a process called interferometry, which combines observations from multiple telescopes into one image. Seeing into the heart of our galaxy turned out to be a bit more complicated than staring down the barrel of a black hole in the next galaxy cluster over, which is why M87’s portrait is out first. Because M87 is one of the nearest, biggest black holes, the team also decided to aim the telescope there, hoping to eventually compare the two bruisers. Called Sagittarius A*, that black hole is relatively puny compared to M87, containing the mass of just four million suns. The Event Horizon Telescope initially set out to snag an image of the supermassive black hole at the core of our galaxy, the Milky Way. Photograph by NASA and the Hubble Heritage Team (STScI/AURA) Orange on the moon In this Hubble image, the blue jet contrasts with the yellow glow from the combined light of M87's stars and star clusters. The center of M87 glows with a gargantuan cosmic searchlight: a black-hole-powered jet of subatomic particles traveling at nearly the speed of light. “Nature has conspired to let us see something we thought was invisible.” “It’s truly remarkable, it’s almost humbling in a certain way,” Doeleman says. The data also offer some hints about how some supermassive black holes manage to unleash gargantuan jets of particles traveling at near light-speed. One of the chief takeaways is a more direct calculation of the black hole’s mass, which tracks closely with estimates derived from the motion of orbiting stars. Six papers published today in the Astrophysical Journal Lettersdescribe the observational tour de force, the process of achieving it, and the details that the image reveals. “What you are seeing is evidence of an event horizon … we now have visual evidence of a black hole.” “We are delighted to be able to report to you today that we have seen what we thought was unseeable,” added project director Shep Doeleman of the Harvard-Smithsonian Institute for Astrophysics.
“We’ve been studying black holes for so long that sometimes it’s easy to forget that none of us has ever seen one,” National Science Foundation director France Cordova said today during a press conference announcing the team’s achievement, held at the National Press Club in Washington, D.C.
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