For the first time, astronomers have discovered a rear-end collision between two high-speed knots of ejected matter.

They discovered it while piecing together a time-lapse movie of a plasma jet that blasted from a super massive black hole inside a galaxy, which is located at 260 million light-years away from the Earth.

Eileen Meyer of the Space Telescope Science Institute (STScI) in Baltimore, Maryland, said, “Something like this has never been seen before in an extragalactic jet. This will allow us a very rare opportunity to see how the energy of the collision is dissipated into radiation”.

Meyer was fully surprised when he saw a fast knot, with an apparent speed of seven times the speed of light, catching up with the end of a slower moving, but still superluminal, knot along the string. Knots of material in jets ejected from gravitationally compact objects are seen commonly.

Meyer added the rare thing was that motions have been observed with optical telescopes, and so far out from the black hole which was thousands of light-years away.

These kind of extragalactic jets are not well understood. It appears like they transport energetic plasma in a confined beam from the active nucleus of the host galaxy.

The latest analysis has suggested that the shocks produced by collisions within the jet have further accelerated the particles, brightening the regions of colliding material.

They have assembled the video of the jet with two decades’ worth of NASA Hubble Space Telescope pictures of the elliptical galaxy NGC 3862.

NGC 3862 is the sixth brightest galaxy. It is one of only a few active galaxies with jets seen in visible light. Hubble discovered the jet in 1992 in optical light.