Monster Black Holes: Most Massive Ever Discovered

Scientists have discovered the largest black holes yet, and they're far bigger than researchers expected based on the galaxies in which they were found.

The discovery suggests we have much to learn about how monster black holes grow, scientists said.

All large galaxies are thought to harbor super-massive black holes at their hearts that contain millions to billions of times the mass of our sun.

Until now, the largest black hole known was a mammoth dwelling in the giant elliptical galaxy Messier 87.

This black hole has a mass 6.3 billion times that of the sun.

The scientists used the Gemini and Keck observatories in Hawaii and the McDonald Observatory in Texas to monitor the velocities of stars orbiting around the centers of a pair of galaxies.

These velocities reveal the strength of the gravitational pull on those stars, which in turn is linked with the masses of the black holes lurking there.

The new findings suggest that one galaxy, known as NGC 3842, the brightest galaxy in the Leo cluster of galaxies nearly 320 million light years distant, has a central black hole 9.7 billion solar masses large.

The other, named NGC 4889, the brightest galaxy in the Coma cluster more than 335 million light years away, has a black hole of comparable or larger mass. Both encompass regions or "event horizons" about five times the distance from the sun to Pluto.

"For comparison, these black holes are 2,500 times as massive as the black hole at the center of the Milky Way galaxy, whose event horizon is one-fifth the orbit of Mercury," said study lead author Nicholas McConnell at the University of California, Berkeley.

Astronomers had suspected that black holes more than 10 billion solar masses large exist, based on light from quasars, cosmic objects from