Astronomers have spotted a collision between two knots of matter ejected from a supermassive black hole.
The black hole is located inside a galaxy 260 million light-years from Earth, and Hubble’s observation allows scientists a new insight into the behavior of these jets of matter, which are not currently understood very well.
Scientists surprised by Hubble’s observations
Scientists put together a video of the jet using 20 years’ worth of images taken by the NASA Hubble Space Telescope. Their work revealed a collision between matter inside the jet, and analysis suggests that the shocks produced by these collisions cause particles to accelerate even further.
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This specific jet has a string-of-pearls structure, and analysis showed one knot catching up with another, to the surprise of Eileen Meyer of the Space Telescope Science Institute (STScI) in Baltimore, Maryland. “Something like this has never been seen before in an extragalactic jet,” said Meyer. She said that the collision caused the knots to brighten considerably, a process that will continue over the next few decades.
Gravitationally compact objects sometimes eject knots of material in jets, but it is uncommon to observe them with optical telescopes like Hubble, and so far away from their black hole. It is thought that material falls onto the object and becomes superheated, before being ejected in a jet due to powerful magnetic fields which constrain it.
Series of knots instead of constant stream
Should the material not fall at a constant rate, the jet of material is ejected as a series of knots rather than a steady flow. This marks only the second time that the phenomenon has been measured so far away from the black hole where it originated, showing that they still travel at near to the speed of light over huge distances.
This information helps scientists to understand the evolution of galaxies as the universe ages. Meyer is currently working on videos, constructed from Hubble images, for two more jets in order to search for further examples of the phenomenon. Extragalactic jets such as this one are seldom seen in optical light by space telescopes like Hubble, and astronomers do not know why some of their number are visible in such conditions and others are not.
The journal Nature reported the results of Meyer’s work in its May 28 issue.