![]() But seeing Sagittarius A* is just a bit more extraordinary for many. “Going from a sample of one to two is a big jump,” said Sarah Gallagher of Western University, an astrophysicist who was not part of the EHT collaboration.īoth observations are glorious in their own right: beautiful results that are “an affirmation of the scientific process,” said Gallagher. Now that we’ve directly seen this black hole, scientists will probe its intricacies and compare it to its much larger sibling inside M87. It allowed astronomers to peer through the hot gas surrounding a supermassive black hole, but it also provided the necessary resolution to reveal the shadow resulting from its event horizon - the point at which no light can escape. “That wavelength is a sweet spot,” said Carl Gwinn, an astrophysicist at the University of California, Santa Barbara who was not involved in the result. Except in this case, the observations were performed at a wavelength of 1.3 millimeters rather than the wavelength of visible light. The spread-out telescopes can create sharper images, just as a larger mirror on an optical telescope affords better views. The EHT uses a technique called very-long-baseline interferometry to produce its images, turning Earth into a giant virtual telescope by combining the views of multiple observatories from the South Pole to Spain. Instead, more than 1,000 hard drives were physically transported back to two processing facilities, one at the Haystack Observatory near Boston, and another at the Max Planck Institute for Radio Astronomy in Bonn, Germany. The resulting files were too large to go out over the internet. ![]() The volume of information collected was enormous, said Lindy Blackburn, an EHT data scientist at the Harvard-Smithsonian Center for Astrophysics - billions of gigabytes’ worth. Eight telescopes gathered views of Sagittarius A* over the course of 10 consecutive nights. The new images were taken in April 2017 during the same window in which the EHT was taking the now-famous image of M87’s black hole. “These results are coming five years after the observations.” “It took us two years to publish the M87 results,” said Huib Jan van Langevelde of Leiden University in the Netherlands, director of the EHT. “The material was swirling around Sag A* so quickly that Sag A*’s appearance could change from minute to minute,” said Katie Bouman, a computer scientist now at the California Institute of Technology who helped develop an algorithm to turn vast amounts of EHT data into an image. Because it is relatively small, any activity on Sagittarius A* - such as the motion of the trillion-degree plasma that surrounds it - occurs 1,000 times faster than it does on M87’s black hole. Sagittarius A* is small - just 30 times wider than our sun - and 27,000 light-years distant. ![]() In order to take an image of Sagittarius A*, the researchers had to confront unique observational challenges. No matter their size, or the environment they live in, once you arrive at the edge of a black hole, gravity takes over.” “This similarity reveals to us a key aspect of black holes. “We were amazed that Sag A* looked so similar to the famous black hole in the M87 galaxy,” said Issaoun. But despite these differences, the two images look remarkably alike.
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