Today, more than three years after the release of the first-ever image of a black hole, scientists from the Event Horizon Telescope (EHT) shared an image of Sagittarius A* (pronounced A-star) — the supermassive specimen sitting at the center of our own Milky Way galaxy.
“It is a dream that comes true after decades of work,” said Heino Falcke, an astrophysicist at Radboud University in the Netherlands. “I always knew this day would come, but I never expected it to be so clear and impressive right away.”
The image immediately reveals new information about the Milky Way’s monster. “The major things we found out about Sag A* were: Is the black hole spinning? Yes, it is,” said Sara Issaoun, an astrophysicist and member of the EHT team. “And what is the orientation of the black hole with respect to us? Now we are fairly confident it is pointed more or less face on to us,” with one of the poles pointed in our direction.
The black hole shown in the new image is vastly different from the one in the earlier photo. The other black hole sits in the center of M87, an enormous elliptical galaxy that’s significantly more massive than our spiral-shaped Milky Way. That black hole fires out a vast jet powered by intense magnetic fields.
Sagittarius A*, by contrast, is 1,000 times less massive than M87’s black hole — 4 million versus 6.5 billion solar masses — making it much harder to see despite its relative proximity. And with less matter swirling around it, Sagittarius A* is dimmer as well. “It’s got a very low mass supply,” said Roger Blandford, an astrophysicist at Stanford University who is not involved with the EHT. “It’s been starved, essentially.”
