The first image of Sagittarius A*, the gargantuan black hole spinning away at the center of our own galaxy, the Milky Way, was released on Thursday by scientists collaborating on the massive Event Horizon Telescope (EHT) project.
Located roughly 27,000 light-years from Earth, Sagittarius A*, or Sgr A*, is thought to be roughly 4 million times the mass of our Sun.
Everything in our 13.6 billion-year-old galaxy orbits Sagittarius A*, including our solar system.
Scientists have inferred its existence at the center of our galaxy for decades based on how objects move around the black hole. But this is the first time we have a direct image of its shadow, even more proof of life of the nexus of our cosmic neighborhood.
Although we cannot see the black hole itself, because it is completely dark, glowing gas around it reveals a telltale signature: a dark central region (called a “shadow”) surrounded by a bright ring-like structure.
Black Hole Sagittarius A* four million times bigger than the Sun
The new view captures light bent by the powerful gravity of the black hole, which is four million times more massive than our Sun.
“We were stunned by how well the size of the ring agreed with predictions from Einstein’s Theory of General Relativity,” said EHT Project Scientist Geoffrey Bower from the Institute of Astronomy and Astrophysics, Academia Sinica, Taipei.
“These unprecedented observations have greatly improved our understanding of what happens at the very center of our galaxy, and offer new insights on how these giant black holes interact with their surroundings,” Bower said.
The EHT team’s results are being published today in a special issue of The Astrophysical Journal Letters.
Because the black hole is so far away from Earth, it appears to us to have about the same size in the sky as a donut on the Moon.
To image it, the team created the powerful EHT, which linked together eight existing radio observatories across the planet to form a single “Earth-sized” virtual telescope. The EHT observed Sgr A* on multiple nights, collecting data for many hours in a row, similar to using a long exposure time on a camera.
The breakthrough follows the EHT collaboration’s 2019 release of the first image of a black hole, called M87*, at the center of the more distant Messier 87 galaxy.
The two black holes look remarkably similar even though our galaxy’s black hole is more than a thousand times smaller and less massive than M87*.
“We have two completely different types of galaxies and two very different black hole masses, but close to the edge of these black holes they look amazingly similar,” says Sera Markoff, Co-Chair of the EHT Science Council and a professor of theoretical astrophysics at the University of Amsterdam, the Netherlands.
Markoff says that “This tells us that General Relativity governs these objects up close, and any differences we see further away must be due to differences in the material that surrounds the black holes.”
Black hole in our Milky Way galaxy
The Milky Way is the galaxy that includes our Solar System, with the name describing the galaxy’s appearance from Earth: a hazy band of light seen in the night sky formed from stars that cannot be individually distinguished by the naked eye.
From Earth, the Milky Way appears as a band because its disk-shaped structure is viewed from within.
Galileo Galilei first resolved the band of light into individual stars with his telescope in 1610. Until the early 1920s, most astronomers thought that the Milky Way contained all the stars in the Universe.
Following the 1920 Great Debate between the astronomers, Harlow Shapley and Heber Curtis, observations by Edwin Hubble showed that the Milky Way is just one of many galaxies.
What does a black hole sound like?
Last week, NASA released an audio of the sound emitted from a black hole at the center of the Perseus galaxy cluster more than 200 million light-years away from Earth.
Perseus is known to be an 11 million-light-year-wide bundle of hundreds of galaxies shrouded by hot gas.
Scientists have released the eerie, Hans Zimmer-like audio captured from a black hole at the centre of the Perseus galaxy cluster 🔭🌌
— Sky News (@SkyNews) May 6, 2022