Tour: Spotted: 'Death Star' Black Holes in Action

Huge black holes are firing powerful beams of particles into space — and then changing their aim to fire at new targets. This discovery, made using NASA’s Chandra X-ray Observatory and the Very Long Baseline Array, shows what kind of widespread impact black holes can have on their surrounding galaxy and beyond.

A team of astronomers looked at 16 black holes in galaxies surrounded by hot gas detected in X-rays by Chandra. Using radio data, they studied the directions of beams — also known as jets — of particles fired a few light-years away from the black holes. This gave the scientists a picture of where each beam is currently pointed, as seen from Earth. Each black hole fires two beams in opposite directions.

The team then used Chandra data to study pairs of cavities, or bubbles, in the hot gas that were created in the past by the beams pushing gas outwards. The locations of large outer cavities indicate the pointing direction of beams millions of years earlier. The researchers then compared the directions of the radio beams with the directions of the pairs of cavities.

They found that about a third of the beams are now pointing in completely different directions than before. These so-called death star black holes are swiveling around and pointing at new targets.

The X-ray and radio data indicate that the beams can change directions over nearly 90 degrees in some cases, and over timescales between one million years and a few tens of millions of years. Considering that these black holes are likely more than 10 billion years old, astronomers consider a large change in direction over a few million years to be fast.

Scientists think that beams from black holes and the cavities they carve out play an important role in how many stars form in their galaxies. The beams pump energy into the hot gas in and around the galaxy, preventing it from cooling down enough to form huge numbers of new stars. If the beams change directions by large amounts, they can tamp down star formation across much larger areas of the galaxy.