A pair of Maunakea observatories were integral to the first-ever image of the black hole at the center of the Milky Way.
A collection of eight radio observatories around the world, collectively called the Event Horizon Telescope Collaboration, released on Thursday an image of Sagittarius A*, the long-hypothesized supermassive black hole around which our entire galaxy revolves.
Sagittarius A* is the second black hole ever to be imaged in this way, the first of which was M87*, also known as Powehi, which was also photographed by EHT.
Among the EHT component observatories were the James Clerk Maxwell Telescope and the Submillimeter Array on Maunakea, which together formed the western extremity of an “Earth-sized” telescope powerful enough to capture an image of the black hole 27,000 light-years away.
“JCMT and SMA provide the western baseline for EHT,” said JCMT Head of Operations Harriet Parsons. “You get a better resolution the wider the array is, so Hawaii has always been instrumental for Event Horizon.”
Parsons said the images of Sagittarius A* and Powehi were both generated from data collected in 2017. However, the Powehi data was much easier to resolve into an image, despite that object being nearly 2,000 times more distant.
“Part of the reason it was easier is because it’s so much bigger than SgrA*,” Parsons said, using a shorthand to refer to Sagittarius A*. “It takes gas days to orbit around M87*, but only minutes to orbit around SgrA*. And that makes things a lot more blurry.”
Furthermore, looking inward from Earth toward the center of the galaxy requires looking through an expanse of space dense with gas, stars and other objects, Parsons added.
But the achievement is significant, Parsons said.
“It’s special for astronomers, because it’s our black hole,” Parsons said. “It’s in our backyard.”
Because of the extreme difference in the masses of Powehi and SgrA*, scientists now have the opportunity to compare how forces like gravity operate at opposite ends of the black hole scale, Parsons said. While SgrA* has the mass of about 4 million suns, Powehi has the mass of about 6.5 billion suns — “like comparing an elephant to an ant,” Parsons said.
However, a less unwieldy name for Sagittarius A* may not be decided on for a while. Powehi was named by Larry Kimura, an associate professor at the University of Hawaii at Hilo, at a request from the JCMT deputy director at the time — although the black hole has not been given an official name by the International Astronomical Union. Because of the COVID-19 pandemic during the intervening time, the same has not yet happened for SgrA*, Parsons said.
Parsons said she hopes a naming decision can be made soon for the black hole.
Email Michael Brestovansky at mbrestovansky@hawaiitribune-herald.com.
