Hubble video shows near-light-speed collision inside black hole jet


Hubble astronomers have captured a near-light-speed collision between two collections of matter ejected from a supermassive black hole 260 million light-years from Earth.

The jets ejected from these vast black holes are so energised that they appear to travel at speeds several times the speed of light – an optical illusion due to the very fast real speed of the plasma, which is close to the universal maximum of the speed of light.

Scientists don't know that much about the jets but the latest analysis suggests that collisions within the jet further accelerate particles and brighten the regions of colliding material.

The video of the jet (above) was assembled with two decades' of NASA Hubble Space Telescope images of the elliptical galaxy NGC 3862, the sixth brightest galaxy and one of only a few active galaxies with jets seen in visible light.

The jet was discovered in optical light by Hubble in 1992. NGC 3862 is in a rich cluster of galaxies known as Abell 1367.

Eileen Meyer of the Space Telescope Science Institute in Baltimore, Maryland, matched archival Hubble images with a new, deep image taken in 2014 to better understand jet motions.

Meyer was surprised to see a fast knot of matter with an apparent speed of seven times the speed of light catch up with the end of a slower moving knot along the string.

The resulting "shock collision" caused the merging blobs to brighten significantly.

"Something like this has never been seen before in an extragalactic jet," said Meyer. As the knots continue merging they will brighten further in the coming decades. "This will allow us a very rare opportunity to see how the kinetic energy of the collision is dissipated into radiation."

While scientists aren't sure how it works, the believe that a knot of matter launched later that the first may have less drag from the ejected interstellar medium and catch up to the earlier knot, rear-ending it.

The collision will continue to play out over the next few decades.

Extragalactic jets have been detected at X-ray and radio wavelengths in many active galaxies powered by central black holes, but only a few have been seen in optical light.

Meyer's results are being reported in today's issue of the journal Nature.

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