M87* sits in a galaxy that is offset from our own, making it easier to see. The fact that Sgr A* lies in our own galaxy also presented an imaging challenge. (Similarly, it’s harder to photograph a dog chasing its tail than one running at the same speed around a large park.) As Sgr A* is 1,500 times smaller than M87*, its speeding light is much harder to resolve. However, it took far more time and effort to bring Sgr A* into focus, due to its smaller size and its location within our own galaxy.Īstronomers suspect that hot gas circles both black holes at the same velocity, close to the speed of light. The images of both black holes are based on data taken by the EHT of the respective sources in 2017. “We now have a consistent image that looks like general relativity is working on both ends of supermassive black holes,” says EHT collaboration member Kazunori Akiyama, a research scientist at MIT’s Haystack Observatory. The similarity between the two images confirms another prediction of general relativity: that all black holes are alike, no matter their size. And yet the image of M87* reveals a bright ring structure, much like Sgr A*. M87* is a goliath compared to Sgr A*, with a mass of 6.5 billion suns (more than 1,000 times heavier than our own black hole), and a size that could easily swallow the entire solar system. That groundbreaking image was of M87*, the supermassive black hole at the center of Messier 87, a galaxy located 53 million light years from Earth. The new image of Sgr A* follows the first-ever image of a black hole, which was obtained by the EHT in 2019. The findings are the result of work by more than 300 researchers from 80 institutions, including MIT, which together make up the Event Horizon Telescope Collaboration. The image and accompanying analyses are presented today in a number of papers appearing in a special issue of The Astrophysical Journal Letters. “The result is a milestone in our understanding of black holes in general and the one at the center of our galaxy in particular.” “It is notoriously difficult to reconstruct images from a widely dispersed array like the EHT, and both rigor and ingenuity have been required to properly understand and quantify uncertainties,” says Colin Lonsdale, director of MIT’s Haystack Observatory. The image revealed today provides the first visual evidence that the object is a black hole, with dimensions that agree with predictions based on Einstein’s theory of general relativity. Astronomers previously have observed stars circling around an invisible, massive, and extremely dense object - all signs pointing to a supermassive black hole. The image is the first visual confirmation that a black hole indeed exists at the center of our galaxy. Judging from the ring’s dimensions, Sgr A* is roughly 4 million times the mass of the sun and incredibly compact, with a size that could fit within the orbit of Venus. The ring’s white-hot plasma is estimated to be 10 billion Kelvin, or 18 billion degrees Fahrenheit. The bright ring encircles a dark center, described as the black hole’s “shadow.” This ring structure lies just outside the event horizon, or the point beyond which light cannot escape, and is the result of light being bent by the black hole’s enormous gravity. The resulting image reveals Sgr A* for the first time, in the form of a glowing, donut-shaped ring of light. The researchers focused the EHT array on the center of our galaxy, 27,000 light years from Earth, cutting through our planet’s atmosphere and the turbulent plasma beyond our solar system. The image was created by the Event Horizon Telescope (EHT) - a global network of radio telescopes whose movements are choreographed so they function as one virtual, planet-sized telescope. Now an international team of astronomers, including researchers at MIT’s Haystack Observatory, has captured the light around our own supermassive black hole, revealing for the first time, an image of Sagittarius A* (Sgr A*, pronounced ‘sadge-ay-star’), the black hole at the heart of the Milky Way galaxy. But just beyond a black hole’s point of no return, light persists, and its patterns, like a photo negative, can reveal a black hole’s lurking presence. Their pull is inescapable, forever trapping any light that falls into their gravitational abyss.
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