Sagittarius A*. This image was taken with NASA’s Chandra X-Ray Observatory. Credit: Public domain
A team of researchers from around the world is getting ready to create what might be the first image of a black hole. The project is the result of collaboration between teams manning radio receivers around the world and a team at MIT that will assemble the data from the other teams and hopefully create an image. The project has been ongoing for ~20 years as members have sought to piece together the Event Horizon Telescope (EHT).
Each of the 12 participating radio receiving teams will use equipment that has been installed for the project to record data received at a wavelength of 230GHz during April 5 through the 14th. The data will be recorded onto hard drives which will all be sent to MIT Haystack Observatory in Massachusetts, where a team will stitch the data together using a technique called very long baseline array VLBA interferometry—in effect, creating the illusion of a single radio telescope as large as the Earth. The black hole they will all focus on is the one believed to be at the center of the Milky Way galaxy— Sagittarius A*.
A black hole cannot be photographed, of course, light cannot reflect or escape from it, thus, there would be none to capture. What the team is hoping to capture is the light that surrounds the black hole at its event horizon, just before it disappears. Sagittarius A* is ~26,000 light-years from Earth and is believed to have a mass ~4 million times greater than the sun—it is also believed that its event horizon is approximately 12.4 million miles across. Despite its huge size, it would still be smaller than a pin prick against our night sky, hence the need for the array of radio telescopes.
The researchers believe the image that will be created will be based on a ring around a black blob, but because of the Doppler effect, it should look to us like a crescent. Processing at Haystack is expected to take many months, which means we should not expect to see an image released to the press until sometime in 2018.
https://phys.org/news/2017-02-scientists-readying-image-black-hole.htmljCp
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