NASA | Goddard | STScI | HubbleSite | 2015 May 27
[youtube]https://www.youtube.com/watch?v=nf7W-WfKxLM[/youtube]When you’re blasting though space at more than 98 percent of the speed of light, you may need driver’s insurance. Astronomers have discovered for the first time a rear-end collision between two high-speed knots of ejected matter. This discovery was made while piecing together a time-lapse movie of a plasma jet blasted from a supermassive black hole inside a galaxy located 260 million light-years from earth.
[img3="Credit: NASA, ESA, and E. Meyers (STScI)
Acknowledgment: NASA, ESA, and G. Bacon (STScI)"]http://imgsrc.hubblesite.org/hu/db/imag ... _print.jpg[/img3][hr][/hr]
The finding offers new insights into the behavior of “light saber-like” jets that are so energized that they appear to zoom out of black hole at speeds several times the speed of light. This “superluminal” motion is an optical illusion due to their being pointed very close to our line of sight and very fast speeds.
Such extragalactic jets are not well understood. They appear to transport energetic plasma in a confined beam from the active nucleus of the host galaxy. The new analysis suggests that shocks produced by collisions within the jet further accelerate particles and brighten the regions of colliding material.
The video of the jet was assembled with two decades’ worth 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, located in the constellation Leo.
The jet from NGC 3862 has a string-of-pearls structure of glowing knots of material. Taking advantage of Hubble's sharp resolution and long-term optical stability, Eileen Meyer of the Space Telescope Science Institute (STScI) in Baltimore, Maryland assembled a video from archival data to better understand jet motions. Meyer was surprised to see a fast knot with an apparent speed of seven times the speed of light catch up with the end of a slower moving, but still superluminal, knot along the string.
The resulting “shock collision” caused the merging blobs to brighten significantly. ...
A kiloparsec-scale internal shock collision in the jet of a nearby radio galaxy - Eileen T. Meyer et al
- Nature 521(7553) 495 (28 May 2015) DOI: 10.1038/nature14481 (pdf)