Scaled laboratory experiments explain the kink behaviour of the Crab Nebula jet

December 20, 2016 by Paul Rivenberg, Massachusetts Institute of Technology
This mosaic image of the Crab Nebula was taken by NASA's Hubble Space Telescope. Features of this nebula and other astrophysical phenomena are being studied at MIT's Plasma Science and Fusion Center. Credit: NASA / ESA / J. Hester / Arizona State University

Senior research scientist Chikang Li wants to experiment with the stars. Intrigued by a curious "kink" phenomenon observed in the Crab Nebula, an interstellar cloud of gas and dust that formed in the wake of a supernova explosion, he has been looking for answers. Images from the Chandra X-ray observatory show that a jet of plasma pouring straight out from the neutron star at the center of the nebula appears to change direction every few years, without changing its structure. Why? Scientists have hypothesized that magnetic fields with the right properties could explain this behavior, but Li wanted proof.

"How do you design an experiment on Earth to explain mysteries that are happening 6,500 light years away, and stretching over 13 light years of space?" he asks. "Traditional astrophysics is based on observation. Typically after you make an observation, you build a theoretical model, you do some numerical simulations. But that's it. How can you go there and measure anything? How can you do an experiment to test this model?"

Li has been part of MIT's Plasma Science and Fusion Center (PSFC) since becoming a graduate student in 1987. As a co-founder and associate head of the PSFC's High-Energy-Density Physics (HEDP) Division, Li has collaborated regularly with the National Ignition Facility and the University of Rochester's Laboratory for Laser Energetics on and laboratory-astrophysical experiments. He decided to see if he could also use the lab's OMEGA laser to mimic the conditions in the Crab Nebula, and prove the hypothesis that magnetic fields were responsible for the "kink in the crab".

Instead of training OMEGA's multiple laser beams on a single pellet of hydrogen fuel, as he would for a , Li bounced lasers off two 3 x 3 mm foils hinged together at a 60-degree angle. Using two laser beams to heat each side, he generated plasma bubbles, or plumes. Li knew that because they are very dense and hot, these plumes would immediately expand, colliding in the middle plane between the two foils to form a jet.

Scaled laboratory experiments explain the kink behaviour of the Crab Nebula jet
Side-by-side images of the jet from the Crab Nebula show its directional change between Nov. 5, 2008 (left) and May 11, 2011. Credit: NASA / CXC / SAO

Li notes that even though laboratory-generated jets and astrophysical jets have very different size scales, the fundamental physics can be the same because critical dimensionless parameters are similar. As a result, they share enough physical properties to allow Li to scale his laboratory experiments, as one would do from a wind tunnel to an airplane, to conditions in the .

While the kink in the nebula jet occurs over a period of a few years, the laboratory experiment creates a jet in one nanosecond (billionth of a second), which then propagates for five to six nanoseconds. Li laughs as he considers the speed of the experiments: "You have to generate that, diagnose that, characterize that, quantify that in this period of time!"

To measure the magnetic fields generated by the experiment, Li used a monoenergetic proton radiography (MPR) diagnostic invented by his division in 2005, allowing him, through the deflection of the protons, to make a radiograph of the fields. With the quantitative measurements in hand, he has been able to prove that the nebula jet behavior is governed by along the jet, which keep its structure largely straight, and other magnetic fields circling around the jet, which create the instability responsible for the directional change. The results were recently published in Nature Communications.

HEDP division head Richard Petrasso noted the importance of Li's work: "Through his understanding of instabilities and his development of the MPR diagnostic to map transient magnetic fields in the laboratory, Chikang has been able to explore and explicate, for the first time, such puzzling phenomena as the jetting in the Crab Nebula."

Explore further: Pulsar wind nebulae

More information: C. K. Li et al. Scaled laboratory experiments explain the kink behaviour of the Crab Nebula jet, Nature Communications (2016). DOI: 10.1038/ncomms13081

Related Stories

Pulsar wind nebulae

November 7, 2016

Neutron stars are the detritus of supernova explosions, with masses between one and several suns and diameters only tens of kilometers across. A pulsar is a spinning neutron star with a strong magnetic field; charged particles ...

Hubble captures the beating heart of the Crab Nebula

July 7, 2016

Peering deep into the core of the Crab Nebula, this close-up image reveals the beating heart of one of the most historic and intensively studied remnants of a supernova, an exploding star. The inner region sends out clock-like ...

A dead star's ghostly glow

October 27, 2016

The eerie glow of a dead star, which exploded long ago as a supernova, reveals itself in this NASA Hubble Space Telescope image of the Crab Nebula. But don't be fooled. The ghoulish-looking object still has a pulse. Buried ...

Peering into cosmic magnetic fields

January 22, 2015

The generation of cosmic magnetic fields has long intrigued astrophysicists. Since it was first described in 1959, a phenomenon known as Weibel filamentation instability—a plasma instability present in homogeneous or nearly ...

Recommended for you

Information engine operates with nearly perfect efficiency

January 19, 2018

Physicists have experimentally demonstrated an information engine—a device that converts information into work—with an efficiency that exceeds the conventional second law of thermodynamics. Instead, the engine's efficiency ...

Team takes a deep look at memristors

January 19, 2018

In the race to build a computer that mimics the massive computational power of the human brain, researchers are increasingly turning to memristors, which can vary their electrical resistance based on the memory of past activity. ...

Artificial agent designs quantum experiments

January 19, 2018

On the way to an intelligent laboratory, physicists from Innsbruck and Vienna present an artificial agent that autonomously designs quantum experiments. In initial experiments, the system has independently (re)discovered ...

7 comments

Adjust slider to filter visible comments by rank

Display comments: newest first

Chris_Reeve
Dec 20, 2016
This comment has been removed by a moderator.
cantdrive85
1.7 / 5 (6) Dec 20, 2016
"Traditional astrophysics is based on observation. Typically after you make an observation, you build a theoretical model, you do some numerical simulations. But that's it. How can you go there and measure anything? How can you do an experiment to test this model?"

Lest we not forget the foundation of modern astrophysics, the "thought experiment".
cantdrive85
2.1 / 5 (7) Dec 20, 2016
As a result, they share enough physical properties to allow Li to scale his laboratory experiments, as one would do from a wind tunnel to an airplane, to conditions in the crab nebula."

Exactly what Birkeland, Alfven, Peratt, Thornhill, et al have done for over 100 years now. Shame on them for suggesting plasma actually behaves like plasma...
cantdrive85
2.7 / 5 (7) Dec 21, 2016
Well Chris, I guess it's just you and me. There's no mention of DM, DE, black holes, or magical gravity, just good honest science using lab experimentation to validate observation. You know, real science ILO the theoretical pseudoscientific mumbo jumbo astrophysicists typically produce. Seems all the pop-sci-fi fans aren't interested, why am I not surprised?
Captain Stumpy
5 / 5 (5) Dec 21, 2016
@reeve/hannes and the rest of you eu nutjobs
It seems that phys.org's editorial is taking its own stance -- in contradiction to its vocal "base" in the comments
no, you moron... this is science as it is always done

this is science like you absolutely refuse to do
and that the eu absolutely cannot do

unlike you eu idiots who make claims repeatedly no matter how much evidence refutes your claims... this is simply yet another study that pushes the frontiers of knowledge outward

and in time, it may well be validated through second party evaluation and experimentation

this is the scientific method at work
whereas the bulk of eu claims is nothing more than attention seeking narcissistic Dunning-Kruger based delusional rants suckering money out of the ignorant like yourselves

FOAD

2Bcont'd
Captain Stumpy
5 / 5 (4) Dec 21, 2016
@nazi sympathizing conspiracist illiterate idiot
the theoretical pseudoscientific mumbo jumbo astrophysicists typically produce. Seems all the pop-sci-fi fans aren't interested, why am I not surprised?
a very Special note for the nazi sympathizer idiot

the above authors/locations are ref's that i've linked to you before proving you're wrong about modern astro's

in fact, Department of Astronomy and Astrophysics, University of Chicago, Department of Physics and Plasma Science and Fusion Center, Massachusetts Institute of Technology were specifically linked on more than one occasion to prove not only magnetic reconnection, but also that astro's know plasma physics

so the real question is:
why aren't you denigrating this article and study as being false since you've repeatedly stated they're all idiots in the past?

i say again - this here is why real scientists usually just ignore you eu idiots
eu=pseudoscience
cantdrive85
3.4 / 5 (5) Dec 27, 2016
Well, a week later and it would seem I was correct. Experimentation is just a bit too real for pop-sci-fi dark matter fans. There is no room for the typical fairy tales and blaming it on some "dark tail wagger". It's just plasma being plasma, as one (not astrophysicists) should expect. Here is more lab based experiment/hypothesis real science, ILO the typical thought experiments by fanciful guessers.
https://www.youtu...HHHTwAyM
Hmmm, how refreshing!

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.