Nearly naked black hole exposed by galactic close encounter

CHARLOTTESVILLE, Va., Nov. 2 (UPI) -- Supermassive black holes are usually hidden away at the center of galaxies. But researchers at the National Radio Astronomy Observatory have discovered a black hole surrounded by relatively little galactic material. It's nearly naked, they say.

According to a new paper published in the Astrophysical Journal, the black hole's home galaxy was stripped of material by a close encounter with a much larger galaxy.

What's left of the black hole's galactic clothing stretches just 3,000 light-years across. The Milky Way, for comparison, is 100,000 light-years across.

The unmasked black hole is surprising, not just for its limited galactic insulation, but because the black hole is fleeing the close encounter at a speed of 2,000 miles per second -- still intact.

When two galaxies collide, more often than not the resident black holes become locked in orbit, collide and merge.

"We were looking for orbiting pairs of supermassive black holes, with one offset from the center of a galaxy, as telltale evidence of a previous galaxy merger," James Condon, a scientist at NRAO, said in a news release. "Instead, we found this black hole fleeing from the larger galaxy and leaving a trail of debris behind it. We've not seen anything like this before."

Astronomers named the black hole B3 1715+425. It's found near a cluster of galaxies called ZwCl 8193.

The peculiarity of the bare black hole was identified and analyzed using data collected by the National Science Foundation's Very Long Baseline Array, a powerful radio telescope.

"The data we get from the VLBA is very high quality," Condon said. "We get the positions of the supermassive black holes to extremely good precision."

Condon and his colleagues believe B3 1715+425 has a lonely future to look forward to. The black hole and what remains of its surrounding galaxy will soon stop making stars -- its galactic resources now limited. Eventually, it will disappear.

For this reason, researchers believe there may be other objects like B3 1715+425 out there waiting to be discovered.