Is There A Black Hole At The Center Of Our Galaxy?
QUICK ANSWER
Yes, there's a supermassive black hole at the center of the Milky Way called Sagittarius A* (Sgr A*). It contains about 4 million times the mass of our Sun and sits 26,000 light-years from Earth. The Event Horizon Telescope captured the first direct image of Sagittarius A* in May 2022.
The center of our Milky Way galaxy holds a supermassive black hole called Sagittarius A*, pronounced Sagittarius A-star. It has about 4 million times the mass of our Sun and sits 26,000 light-years from Earth in the constellation Sagittarius. We can't see it directly with normal telescopes, but its gravitational effects on nearby stars confirmed its existence decades ago.
How big is Sagittarius A*?
About 4 million solar masses. According to NASA, Sagittarius A* contains roughly 4 million times the mass of our Sun, all compressed into a region smaller than our solar system. The event horizon is about 14 million miles across, larger than the Sun but tiny compared to galactic scales. Despite its enormous mass, Sgr A* is considered modest for a supermassive black hole. Many galaxies host central black holes thousands of times more massive than ours.
How do we know it's there?
From watching nearby stars orbit it. Astronomers have tracked stars near the galactic center for decades, watching them swing around an invisible massive object at extreme speeds. The star S2 makes a complete orbit every 16 years, traveling at up to 5,000 miles per second at closest approach. The orbital data lets astronomers calculate the central mass with high precision: about 4.3 million solar masses concentrated in a tiny region. Two of the astronomers leading this work shared the 2020 Nobel Prize in Physics for the discovery.
Was it ever imaged?
Yes, in May 2022. The Event Horizon Telescope (EHT), a network of radio telescopes around the world, captured the first direct image of Sagittarius A*. The image shows a bright ring of glowing material around a dark central shadow. The shadow is the silhouette of the black hole's event horizon. The result confirmed long-standing predictions from Einstein's general relativity. Sgr A* was the second black hole imaged by the EHT, after M87* in 2019.
Is Sagittarius A* dangerous to Earth?
Not at all. Sgr A* is 26,000 light-years away, far enough that its gravitational influence on Earth is negligible. The Sun orbits the galactic center along with everything else in the Milky Way, taking about 230 million years to complete one orbit. Sgr A* is relatively quiet for a supermassive black hole, with low rates of matter falling in compared to active galactic nuclei in other galaxies. It's not a threat under any plausible scenario.
The center of the Milky Way contains a supermassive black hole called Sagittarius A*, about 4 million times the mass of the Sun and 26,000 light-years from Earth. It was first directly imaged in May 2022, confirming decades of indirect evidence. Sgr A* is relatively small for a supermassive black hole and not dangerous to Earth at our distance. It's the most studied black hole in our galaxy.
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