By Brittany Anderson
The vastness of the universe and everything inside of it can be both exciting and terrifying.
Astronomers recently revealed the first image of the Milky Way’s supermassive black hole Sagittarius A*, or Sgr A* (“Sagittarius A star”), captured with the Event Horizon Telescope. Sgr A* is located in Sagittarius A, which is the center of our galaxy, between the constellations Sagittarius and Scorpius.
Black holes are cosmic bodies that have such an intense gravitational pull that nothing, not even light, can escape it. Supermassive black holes are the largest type of black holes, with its mass being millions to billions of times the mass of our Sun.
Richard Anantua, an astrophysicist and assistant professor of Physics and Astronomy at the University of Texas at San Antonio, spoke to the Hays Free Press/News-Dispatch about the Sgr A* image while — fittingly — at a black hole conference in Kathmandu, Nepal. Anantua has served as a member of the Event Horizon Telescope (EHT) Collaboration, bringing EHT science to Texas.
“Almost all galaxies are thought to have supermassive black holes at their center, including our own,” Anantua said. “We’ve had a lot of indirect lines of evidence that there was one, such as the very eccentric orbits of stars that are near it that we’ve seen, and the material that we’ve seen in the innermost disc around the black hole in infrared wavelengths. But this is the first image where we actually see a central depression going all the way into the horizon. That’s basically what we expect to be around black holes.”
Anantua said that Sgr A* has been a prediction of the theory of gravity that Einstein had that was worked out by a number of individuals: that if you have enough matter within a region, then you can have a one-way surface beyond which light can escape. One of the confirmations of the theory is that matter deforms space in a way that space becomes too curved even for objects of very high escape speeds to escape, even light.
“This is a very important theory that tells us about the fundamental nature of space and time that was thought for many centuries to be absolute, not dependent on how you’re moving or what gravitating object is near it,” Anantua said.
This is the first time a black hole in our galaxy has been seen, and only the second time a black hole has ever been captured. Anantua explained that in 2017, there was light received and data taken from Sgr A*, but astronomers were only confident enough to make the image now after overcoming various engineering and theoretical challenges.
The process of capturing such an image hasn’t been simple. Anantua said that eight ground-based telescopes sensitive to millimeter wavelength light were used, turning the information they were getting from the photons of light after a 27,000-year journey from the galactic center into an image using mathematical procedures that would convert the data coming from space.
According to Anantua, Sgr A* has a four million solar mass, eating very little of the matter that is around it, and the matter that is around it is swirling and magnetized. Its glowing ring is a result of the particles it is launching at high speeds. It’s also rotating and attracting material from around it, or at least influencing material around it to rotate with it.
“The black hole is in a very active place in the galaxy,” Anantua said. “It’s a very complicated, jumbled mess at the center of action in the galaxy. The black hole is directing traffic in some ways, but it’s also causing traffic jams, and causing things to be flung out. It’s also being affected by the things that are falling into it.”
But you can rest easy — the idea of a supermassive black hole existing in our own galaxy might be unnerving, but Sgr A* is 27,000 light years away from Earth, and it’s small in size relative to everything else in the galaxy.
“It’s a very small fraction of the total mass that’s in the galaxy,” Anantua said. “The galaxy might have a trillion solar masses worth of mass, but this [Sgr A*] only has four million solar masses … it’s not really going to affect the path of Earth around the center of the galaxy that much. The speed that we’re going around the center of the galaxy is enough to keep us from falling in, and we’re not slowing down very fast to where we’d have to worry about falling in.”
Although some might look at Sgr A* and only see a fuzzy image of an orange and yellow blob, the intense dedication put in by scientists to capture this supermassive black hole’s existence could lead to more scientific discoveries and an even better understanding of our own galaxy.
“The fact that we could bend space and time with the right matter is something that could form the basis of speculative objects like wormholes,” Anantua said. “Our current technology isn’t suitable to really make any of this right now, but knowing how matter tells space how to curve and space tells matter how to bend, could be the basis for intergalactic travel eventually. It could be the basis for very long-term projects that might have something to do with the ultimate fate of the planet.”
Learn more about Sgr A* and Anantua’s work at .
