Astronomers have finally seen the center of the Milky Way galaxy, unmasking a giant black hole, a celestial vortex 26,000 light-years from Earth that would otherwise be hidden from view.
An international team of researchers released a snapshot of the supermassive black hole known as Sagittarius A* on Thursday., spied on through the power of eight linked radio antennas from around the world that together can penetrate through gas clouds in space. Although black holes are by definition invisible – light cannot travel fast enough to escape their clutches – Sagittarius A* revealed itself as a dark shadow surrounded by the bright glow of gas and debris swirling around its perimeter.
The photo showed a region in deep space reminiscent of a solar eclipse – a darkened circle, shrouded in a radiant red-orange blur of light. The image has been colorized so that human eyes can perceive it.
Until three years ago, any depiction of a black hole was merely an artistic interpretation or computer model of what the spinning and bending phenomenon of spacetime might look like. This object, seen in the photo at the top of this story, is the real deal, with each pixel representing a Herculean effort: hundreds of scientists from 80 institutions around the world, working together to collect, process and piece together bits of data.
The breakthrough was also published in the scientific journal Astrophysical Journal Letters. Spokespersons for the Event Horizon telescope, the international collaboration of 300 scientists who worked on the feat, held simultaneous press conferences in at least seven countries to share the news, including in the United States at the National Press Club in the nation’s capital.
The image of Sagittarius A*, pronounced “Sagittarius A-Star”, is a monumental achievement, the second time scientists have broken through the barrier of invisibility to glimpse a black hole. The first photo, revealed in April 2019, showed the black hole that resides at the center of the Messier 87 galaxy, an easier target to capture due to its size, despite being much farther away, at around 53 million miles away. light years. Astronomers say the black hole, dubbed M87*, is as large as Earth’s eight-planet solar system.
The second photo provides powerful confirmation to the scientific community, said Feryal Özel, professor of astronomy and physics at the University of Arizona.
“Now we know that wasn’t a coincidence – it wasn’t an aspect of the environment that looked like the ring we expected to see,” she said at the event. in Washington, D.C. “We now know that, in both cases, what we see is the heart of the black hole, the point of no return. These two images resemble each other because they are the consequence of the fundamental forces of the gravity.
Astronomers see the first supermassive black hole as it grows
This graph shows how much larger the supermassive black hole in galaxy M87 is than Sagittarius A* (which sits at the center of our galaxy, the Milky Way).
Credit: National Science Foundation/Keyi “Onyx” Li
Sagittarius A*, or Sgr A* for short, is considerably smaller, at around 27 million miles in diameter, but it’s no pipsqueak. Scientists estimate that it is 4 million times more massive than the sun. To make a hard-to-grasp number even more unfathomable, imagine this: the mass of the sun equals 333,000 Earths.
Its home, the Milky Way, a spiral galaxy, is fairly flat, but the center sinks where the supermassive black hole is. All around, stars spin in various directions. But the hole, often anthropomorphized in pop culture as a space monster, is actually quite “soft”, the researchers say, consuming relatively little of its surroundings.
Black holes are among the most elusive things in space. The most common type, called a stellar black hole, is often thought to be the result of the death of a huge star in a supernova explosion. The star material then collapses in on itself, condensing into a relatively small area.
But how supermassive black holes, millions to billions of times more massive than the sun, form is even more mysterious than typical stellar black holes. Many astrophysicists and cosmologists believe these behemoths lurk at the center of virtually every galaxy. Recent observations from the Hubble Space Telescope have bolstered the theory that supermassive black holes originate in the dusty cores of star-shaped galaxies, where new stars are rapidly produced, but scientists are still trying to solve the problem.
Black holes have no surface, like on a planet or a star. Instead they have a boundary called the “event horizon”, it’s a point of no return. If something gets too close, it will fall into it, never escaping the hole’s gravitational pull.
Ahead of the groundbreaking May 12 image, the Event Horizon Telescope team released the first photo of a black hole in the Messier 87 galaxy in April 2019.
Credit: Chip Somodevilla/Getty Images
If M87* offered proof that black holes weren’t science fiction, Sgr A* is the testament to decades of growing observational science. Before the first black hole photo, scientists deduced the presence of a hole in space by detecting its impact on nearby stars and gas. Albert Einstein, whose theory of general relativity predicted black holes more than a century ago, and Stephen Hawking, a cosmologist who has devoted much of his career to mathematically proving their existence, are among the many prominent figures that paved the way for Thursday’s reveal.
If M87* offered proof that black holes weren’t science fiction, Sgr A* is the testament to decades of growing observational science.
Sgr A* is exciting for scientists because it’s ordinary, said Michael Johnson of the Harvard Smithsonian Center for Astrophysics. the central supermassive black hole is representative of many others in the universe, allowing experts to learn more about these mysterious space objects.
Despite their visual similarities — one flaming donut versus another flaming donut — the two black holes couldn’t be more different, the scientists said. M87* is accumulating matter at a much faster rate, but the Milky Way’s central black hole is changing its appearance more quickly: it only takes a few minutes for the gas to completely orbit it, whereas an orbit around its predecessor lasts about two weeks.
In addition, the first photographed black hole launches a huge jet of radiation that extends to the edges of its galaxy, unlike Sgr A*.
To collect the huge amount of data needed to process the new image, the Event Horizon Telescope used a technique called very long baseline interferometry, which synchronizes observatories around the world and takes advantage of the Earth’s rotation to form a planet-sized virtual telescope. . Together, the instruments were able to see the sky with a view comparable to that needed to read a newspaper in New York from Paris, according to the organization.
At the time of the 2019 black hole announcement, Event Horizon Telescope collaborators said they had also attempted to image this supermassive black hole, but the team had been unable to get a clear picture. As one of the most studied supermassive black holes in the universe, it was a disappointment for many astrophysicists who longed to gaze upon the navel of our galaxy.
“For me personally, I met him 20 years ago and loved him and have been trying to figure him out ever since,” Özel said on Thursday.
This time, the scientists added the South Pole Telescope, which was not used in the M87* photo, to the network of virtual telescopes to improve the resolution of their imagery. The researchers gathered five petabytes of data, or about 2.5 trillion pages of printed text, to capture even a glimmer of this black hole, said Dom Pesce, a member of the telescope team.
Simply put, it’s the equivalent amount of data in about 100 million TikTok videos, said MIT Haystack Observatory researcher Vincent Fish. That’s way too much to broadcast on the Internet, so the scientists had to ship hundreds of hard drives to two centers in western Massachusetts and Bonn, Germany, where supercomputers could process the raw data.
Credit: Daniel Michalik / National Science Foundation
Admittedly, the Sgr A* photo is blurry. Johnson compared the blur to looking through ground glass. Radio waves containing crucial image detail are scattered, causing the sharp outline of the hole to look more like a ring of jelly. To solve this problem, telescopes must either be further apart or reach higher frequencies, he said.
“We don’t think the black hole is actually a blurry image in the sky,” Johnson said. “We’re just at our breaking point here.”
“We don’t think the black hole is actually a blurry image on the sky.”
With financial support from the National Science Foundation and other groups, the scientists plan to improve their technology to make the image considerably sharper.
Another next step in the collaboration is to attempt to turn these still images into videos, so scientists can observe how gas falls toward the event horizons of black holes. This project could be completed after 2024, they said.
But in case anyone is disappointed by another flaming donut, Katie Bouman, assistant professor of astronomy at Caltech, recalled the amount of data contained in the image.
“This picture is actually one of the sharpest pictures you’ve ever seen,” she said.