An international team of researchers that depended on expertise from Charlottesville’s National Radio Astronomy Observatory revealed the first-ever image of a black hole on Wednesday.
Several years ago, a team of scientists proposed using ALMA, an array of powerful radio telescopes in the Chilean desert operated in part by Charlottesville researchers, for a project to find the edge of a black hole. On Wednesday, those efforts revealed a blurry, donut-shaped image that outlines a super massive black hole lurking at the heart of the galaxy Messier 87.
“This is a huge milestone for NRAO and for ALMA,” said Anthony Remijan, who manages the North American ALMA Science Center and was part of the commissioning team that made the trek up a mountain in Chile to prepare the array for the Event Horizon Telescope project.
“It’s really amazing to see the final image that came out of that effort from the entire team,” he said.
The field of radio astronomy began in the 1930s as a way to use radio waves to detect objects from distances farther than the eye and visual telescopes could see.
In 1955, the National Science Foundation built the country’s first radio telescope in Green Bank, West Virginia, and in 1964, the foundation began moving some equipment and personnel to new offices at the University of Virginia.
Radio telescopes gather radio wave information from a period of time and piece them together into a visual image.
“It’s not a snapshot; it’s an exposure,” said Charles Blue, a spokesman for the observatory.
Today, Charlottesville houses no NRAO radio telescopes, but scientists and analysts pass through headquarters as they coordinate projects and analyze research. NRAO operates several large arrays of radio telescopes, including ALMA in Chile, VLA in New Mexico and VLBA from sites across the Northern Hemisphere. International efforts often use multiple radio telescopes together, harnessing them to search even wider and see even farther.
The image revealed Wednesday relied on a network of eight telescopes and arrays in multiple countries that stretched across the entire Earth. That network is collectively known as the Event Horizon Telescope.
Two years of data consistently showed the same image, researchers said at a press conference in Washington, D.C., on Wednesday.
Black holes are made up of huge amounts of matter squeezed into a small area, creating a gravitational field that draws in everything around it, including light. The event horizon of black holes is their point of no return, where any matter is sucked inside. Their capture of light makes them impossible to view or photograph through a traditional telescope. But, by linking the telescopes to form an Earth-sized radio disk and tuning each telescope to the same high frequency, researchers could achieve the resolution necessary to pinpoint the radio waves emitting from the ring-shaped silhouette of the black hole.
The image revealed Wednesday displays a glowing ring of gas. The dark center in the image is actually the black hole’s shadow, caused by the gravitational bending and the capture of light of the event horizon.
“Nature has conspired to show us something that we long thought was invisible,” said Shep Doeleman, a senior researcher at Harvard University and director of the Event Horizon Telescope. “The power that we’re seeing, we can’t see it with our own eyes, so we have to use other waves from the electromagnetic spectrum.”
The effort to coordinate ALMA’s telescopes with other telescopes across the world was massive, and also required a tune-up to receive radio waves at higher frequencies. That expertise is appreciated by other researchers, such as Al Wootten, an ALMA scientist who studies early star and planet formation.
“The [event horizon] announcement is pretty exciting and is something we’ve been waiting for for a long time,” Wootten said. “A lot of aspects of UVa went into the array and making the science possible.”
UVa’s Microfabrication Laboratories, part of the School of Engineering & Applied Science, also fabricated detectors for most of the radio receivers on the telescopes.
The discovery confirms a prediction made in Albert Einstein’s general theory of relativity, scientists said, and advances the academic and technical exploration of space.
“Through its leadership in ALMA and long-term support for the EHT, NRAO has once again helped to advance our understanding of the cosmos and the fundamental laws of physics,” Tony Beasley, director of the NRAO, said in a new release Wednesday. “This observation clearly illustrates the value of radio astronomy to scientific advancement.”