It’s easy to think of black holes as inescapable cosmic sinkholes, sucking everything in the vicinity inwards in their vast grip, but their outskirts can also eject violently spectacular jets, streams of plasma that are mysteriously spat out at speeds approaching the speed of light.
An international team of astronomers has now imaged newly forming jets of plasma from a massive black hole with unprecedented accuracy and detail thanks to a super high resolution telescope that allowed them to observe the jet structure 10 times closer to the black hole than ever before. Their results are published this week in Nature Astronomy.
Using RadioAstron – a network of the world's largest telescopes on the ground plus one in space, resulting in a telescope larger than Earth itself – the team managed to capture ultra-high angular resolution images of a jet launching from a black hole in the center of NGC 1275, a giant galaxy 230 million light-years away in the galaxy cluster of Perseus A.
“The result was surprising. It turned out that the observed width of the jet was significantly wider than what was expected in the currently favoured models where the jet is launched from the black hole’s ergosphere – an area of space right next to a spinning black hole where space itself is dragged to a circling motion around the hole,” lead author Professor Gabriele Giovannini from the Italian National Institute for Astrophysics explained in a statement.
“This may imply that at least the outer part of the jet is launched from the accretion disk surrounding the black hole. Our result does not yet falsify the current models where the jets are launched from the ergosphere, but it hopefully gives the theorists insight about the jet structure close to the launching site and clues how to develop the models”, added Dr Tuomas Savolainen from Aalto University in Finland.
Supermassive black holes, with masses more than a million times that of the Sun, appear to be found in the center of all massive galaxies. Nobody is quite sure about how or why these jets form, which is why imaging them during their formation is so important.
Curiously, the jet structure seen in NGC 1275 was significantly different from the jets observed in the relatively close galaxy Messier 87, the only other jet whose structure has been imaged equally close to the black hole. The most viable explanation for this contrasting structure is the difference in age of the two jets.
“The jet in NGC 1275 was re-started just over a decade ago and is currently still forming, which provides a unique opportunity to follow the very early growth of a black hole jet. Continuing these observations will be very important", confirmed co-author Dr Masanori Nakamura from Academia Sinica in Taiwan.