A Princeton-led team of researchers has discovered a revolutionary way to generate high-energy shock waves in the lab.
Peering deep into the core of the Crab Nebula, this Hubble image reveals the beating heart of one of the most historic and intensively studied remnants of a supernova, an exploding star. The neutron star at the very center of the nebula has about the same mass as the Sun but compressed into an incredibly dense sphere that is only a few miles across. Spinning 30 times a second, the neutron star shoots out detectable beams of energy that make it look like it’s pulsating. The Hubble snapshot is centered on the region around the neutron star (the rightmost of the two bright stars near the center of this image) and the expanding, tattered, filamentary debris surrounding it. Hubble’s sharp view captures the intricate details of glowing gas, shown in red, that forms a swirling medley of cavities and filaments. Inside this shell is a ghostly blue glow that is radiation given off by electrons spiraling at nearly the speed of light in the powerful magnetic field around the crushed stellar core. This neutron star is a showcase for extreme physical processes and unimaginable cosmic violence. Bright wisps are moving outward from the neutron star at half the speed of light to form an expanding ring. It is thought that these wisps originate from a shock wave that turns the high-speed wind from the neutron star into extremely energetic particles. Image credit: NASA / ESA / J. Hester, ASU / M. Weisskopf, NASA & MSFC.
Throughout the Universe, supersonic shock waves propel cosmic rays and supernova particles to velocities near the speed of light.
The most high-energy of these astrophysical shocks occur too far outside our Solar System to be studied in detail and have long puzzled scientists.
Shocks closer to Earth can be detected by spacecraft, but they fly by too quickly to probe a wave’s formation.
Now Princeton University researcher Dr. Derek Schaeffer and co-authors have generated the first high-energy shock waves in a laboratory setting, opening the door to new understanding of these mysterious processes.
“We have for the first time developed a platform for studying highly energetic shocks with greater flexibility and control than is possible with spacecraft,” Dr. Schaeffer said.
“This lets you understand the evolution of the physical processes going on inside shock waves,” added co-author Dr. Will Fox, of the U.S. Department of Energy’s (DOE) Princeton Plasma Physics Laboratory.
To produce the wave, the team used a laser to create high-energy plasma — a form of matter composed of atoms and charged atomic particles — that expanded into pre-existing magnetized plasma.
The interaction created, within a few billionths of a second, a magnetized shock wave that expanded at a rate of more than 1 million mph, congruent with shocks beyond the Solar System.
The rapid velocity represented a high ‘magnetosonic Mach number’ and the wave was ‘collisionless,’ emulating shocks that occur in outer space where particles are too far apart to frequently collide.
“Going forward, the laboratory platform will enable new studies of the relationship between collisionless shocks and the acceleration of astrophysical particles,” the authors said.
“The platform complements present remote sensing and spacecraft observations, and opens the way for controlled laboratory investigations of high-Mach number shocks.”
The research was published in the July 14, 2017 issue of the journal Physical Review Letters.
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D.B. Schaeffer et al. 2017. Generation and Evolution of High-Mach-Number Laser-Driven Magnetized Collisionless Shocks in the Laboratory. Phys. Rev. Lett 119 (2): 025001; doi: 10.1103/PhysRevLett.119.025001
