“This is the biggest black hole in the nearby universe,” said astronomer two smaller black holes merging into one.
It probably took a few hundred such mergers to build the beast in M87, said Caltech astronomer George Djorgovski, who was not involved in the new work. In the same press conference, Djorgovski announced 16 new black hole pairs that will probably merge in the next few million years.
Big black holes also have big event horizons, the point at which a black hole’s gravity is so great even light can’t escape. The black hole in M87’s event horizon is about 12 billion miles across, three times the size of Pluto’s orbit.
“This black hole could swallow our solar system whole,” Gebhardt said.
That extensive event horizon would cast a dark shadow on the galactic dust behind it. Future observations with a worldwide network of telescopes looking at wavelengths of light smaller than a millimeter could potentially take a picture of that shadow, proving once and for all that black holes exist.
“We don’t know whether black holes are black holes,” Gebhardt said. “To actually determine whether an object is a black hole, you need to have some type of proof of the event horizon. That doesn’t exist yet. To have an object where we might be able to image it, it’s remarkably important.”
Image: An artist’s rendition of what the black hole’s shadow might look like. Credit: Gemini Observatory/AURA illustration by Lynette Cook