An international team of astronomers has answered a long standing question about the enigmatic jets emitted by black holes, in research published today in the journal Nature.

Jets are narrow beams of matter spat out at high speed from near a central object, like a black hole.

"Although they have been observed for decades, we're still not sure what they are made of, or what powers them," ESO astronomer Dr María Díaz Trigo, lead author of the study, said.

The team studied the radio waves and X-rays emitted by a small black hole a few times the mass of the Sun. The black hole in question was known to be active, but the team's radio observations did not show any jets, and the X-ray spectrum didn't reveal anything unusual.

However, a few weeks later, the team took another look and this time saw radio emissions corresponding to the sudden appearance of these jets, and even more interestingly, lines had appeared in the X-ray spectrum -- the tell-tale signature of ordinary atoms -- around the black hole.

To read more, click here.