Recent observations of blazar jets require researchers to look deeper into whether current theories about jet formation and motion require refinement. This simulation, courtesy of Jonathan McKinney (KIPAC), shows a black hole pulling in nearby matter (yellow) and spraying energy back out into the universe in a jet (blue and red) that is held together by magnetic field lines (green).

World-wide Campaign Sheds New Light on Nature’s “LHC”

11 Mar , 2010 by

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In a manner somewhat like the formation of an alliance to defeat Darth Vader’s Death Star, more than a decade ago astronomers formed the Whole Earth Blazar Telescope consortium to understand Nature’s Death Ray Gun (a.k.a. blazars). And contrary to its at-death’s-door sounding name, the GASP has proved crucial to unraveling the secrets of how Nature’s “LHC” works.

“As the universe’s biggest accelerators, blazar jets are important to understand,” said Kavli Institute for Particle Astrophysics and Cosmology (KIPAC) Research Fellow Masaaki Hayashida, corresponding author on the recent paper presenting the new results with KIPAC Astrophysicist Greg Madejski. “But how they are produced and how they are structured is not well understood. We’re still looking to understand the basics.”

Blazars dominate the gamma-ray sky, discrete spots on the dark backdrop of the universe. As nearby matter falls into the supermassive black hole at the center of a blazar, “feeding” the black hole, it sprays some of this energy back out into the universe as a jet of particles.

Researchers had previously theorized that such jets are held together by strong magnetic field tendrils, while the jet’s light is created by particles spiraling around these wisp-thin magnetic field “lines”.

Yet, until now, the details have been relatively poorly understood. The recent study upsets the prevailing understanding of the jet’s structure, revealing new insight into these mysterious yet mighty beasts.

“This work is a significant step toward understanding the physics of these jets,” said KIPAC Director Roger Blandford. “It’s this type of observation that is going to make it possible for us to figure out their anatomy.”

Over a full year of observations, the researchers focused on one particular blazar jet, 3C279, located in the constellation Virgo, monitoring it in many different wavebands: gamma-ray, X-ray, optical, infrared and radio. Blazars flicker continuously, and researchers expected continual changes in all wavebands. Midway through the year, however, researchers observed a spectacular change in the jet’s optical and gamma-ray emission: a 20-day-long flare in gamma rays was accompanied by a dramatic change in the jet’s optical light.

Although most optical light is unpolarized – consisting of light with an equal mix of all polarizations – the extreme bending of energetic particles around a magnetic field line can polarize light. During the 20-day gamma-ray flare, optical light from the jet changed its polarization. This temporal connection between changes in the gamma-ray light and changes in the optical polarization suggests that light in both wavebands is created in the same part of the jet; during those 20 days, something in the local environment changed to cause both the optical and gamma-ray light to vary.

“We have a fairly good idea of where in the jet optical light is created; now that we know the gamma rays and optical light are created in the same place, we can for the first time determine where the gamma rays come from,” said Hayashida.

This knowledge has far-reaching implications about how a supermassive black hole produces polar jets. The great majority of energy released in a jet escapes in the form of gamma rays, and researchers previously thought that all of this energy must be released near the black hole, close to where the matter flowing into the black hole gives up its energy in the first place. Yet the new results suggest that – like optical light – the gamma rays are emitted relatively far from the black hole. This, Hayashida and Madejski said, in turn suggests that the magnetic field lines must somehow help the energy travel far from the black hole before it is released in the form of gamma rays.

“What we found was very different from what we were expecting,” said Madejski. “The data suggest that gamma rays are produced not one or two light days from the black hole [as was expected] but closer to one light year. That’s surprising.”

In addition to revealing where in the jet light is produced, the gradual change of the optical light’s polarization also reveals something unexpected about the overall shape of the jet: the jet appears to curve as it travels away from the black hole.

“At one point during a gamma-ray flare, the polarization rotated about 180 degrees as the intensity of the light changed,” said Hayashida. “This suggests that the whole jet curves.”

This new understanding of the inner workings and construction of a blazar jet requires a new working model of the jet’s structure, one in which the jet curves dramatically and the most energetic light originates far from the black hole. This, Madejski said, is where theorists come in. “Our study poses a very important challenge to theorists: how would you construct a jet that could potentially be carrying energy so far from the black hole? And how could we then detect that? Taking the magnetic field lines into account is not simple. Related calculations are difficult to do analytically, and must be solved with extremely complex numerical schemes.”

Theorist Jonathan McKinney, a Stanford University Einstein Fellow and expert on the formation of magnetized jets, agrees that the results pose as many questions as they answer. “There’s been a long-time controversy about these jets – about exactly where the gamma-ray emission is coming from. This work constrains the types of jet models that are possible,” said McKinney, who is unassociated with the recent study. “From a theoretician’s point of view, I’m excited because it means we need to rethink our models.”

As theorists consider how the new observations fit models of how jets work, Hayashida, Madejski and other members of the research team will continue to gather more data. “There’s a clear need to conduct such observations across all types of light to understand this better,” said Madejski. “It takes a massive amount of coordination to accomplish this type of study, which included more than 250 scientists and data from about 20 telescopes. But it’s worth it.”

With this and future multi-wavelength studies, theorists will have new insight with which to craft models of how the universe’s biggest accelerators work. Darth Vader has been denied all access to these research results.

Sources: DOE/SLAC National Accelerator Laboratory Press Release, a paper in the 18 February, 2010 issue of Nature.

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Astrofiend
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Astrofiend
March 11, 2010 7:04 PM

Wow – that is a very interesting result indeed. Ball’s in your court, theorists!

The Eclectic Exterminator of Stupid Electricians
Member
The Eclectic Exterminator of Stupid Electricians
March 11, 2010 7:22 PM

Oh Dear. Now we will be again bombarded by all those EU weirdos, and hear their claptrap of irrelevant rubblish. Since black holes don’t exist in the minds of these jackasses, then I suppose whatever they say really doesn’t matter.

One important point though. This phenomena likely only occurs in extreme circumstances, where material is dragged into the vicinity of an accretion disk, accelerated, and expelled through the poles. This forms the strong magnetic field. The black hole itself only acts as the gravitation source vacuuming up the material.

Let the “personal theories” begin, I suppose.

Lawrence B. Crowell
Member
Lawrence B. Crowell
March 11, 2010 8:20 PM

It is curious that the gamma rays are produced so far from the BH. I might conjecture that these result from Bremmstrahlung, or the relativistic case of synchrotron radiation as the highly relativistic charge particles accelerated through the jet interact with a gas cloud.

LC

Dilip G Banhatti
Member
March 12, 2010 1:45 AM

The picture of detailed simulation accompanying the story is rather misleading! The observations are of 20 days of gamma ray flare and optical polarization changes during this flare. Detailed simulations are hardly warranted unless one has mapped the flare in detail (perhaps in radio band). Occam’s razor indicates that a rough model like Scheuer’s dentist’s drill should suffice to explain the observations. In this mdel, the jet changes direction erratically due to bouncing repeatedly on somewhat asymmetric surrounding medium, rather like a dentist’s drill.

Torbjorn Larsson OM
Member
Torbjorn Larsson OM
March 12, 2010 2:21 AM
¨Huh, I had the same reaction as HSBC. Isn’t it awful how the first reaction is “wow, amazing” and the second “wow, wonder what those amazing idjits the [insert pertinent crackpot species here] make of this”. They do train us well with their persistent habituation, don’t they? – “Sit up, roll over, please play intellectually dead. Good reader!” As far as this, again truly amazing, data goes all my personal ideas just failed testing. No twisted jets would have come out of that mess. So good riddance! And now for some new mess. It will be pitiful for the experts, but hey, I must make a passing for now mental model or play as dead as those crackpots… Read more »
SteveZodiac
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SteveZodiac
March 12, 2010 5:34 AM

Torbjorn, I like the reconnection idea, from what little I know of Gamma Ray bursts magnetic fields seem to be strongly implicated. The sheer strength of the fields in these cases would result in an almighty release of energy from any reconnection events.

DrFlimmer
Member
DrFlimmer
March 12, 2010 6:06 AM
Ah, my favorite topic of astrophysics. Great read, very interesting article, thanks Jean!! Reconnection is likely involved, since it is a nice mechanism to transform magnetic energy into kinetic energy. However the field strength are not that “high” in a jet. IIRC, normally one talks about a few Gauss or less. That’s far less than what you need for the LHC (~5 Tesla). In fact, if the particles in the jet are fast enough, they can collimate themselves quite nicely due to relativistic effects. I have read a nice review recently by H. Spruit. It deals with jets, the launching mechanism and the problems involved. Very interesting: http://arxiv.org/abs/0804.3096 If the jets really kink and bend rather quickly, I… Read more »
Aodhhan
Member
Aodhhan
March 12, 2010 7:57 AM

Because I really want to believe (really badly)not only can massless particles exceed the sped of light, but things with mass can as well… I’m going to speculate we cannot see/detect the gamma rays until they are so far out, because they are exceeding the speed of light!
…however as a realist, there is something in my gut telling me not to be shocked if it isn’t due to the massive gravity around a black hole which is bending space time. Since it would be opposite the principle of something falling into it.

DrFlimmer
Member
DrFlimmer
March 12, 2010 8:09 AM
@ Aodhhan: What exactly do you want to say? 1) NOTHING can exceed the speed of light. It’s really that simple. 2) It is not simple for a black hole (no matter how massive it is) to suck down matter. Every piece of matter approaching a black hole has angular momentum with respect to the black hole. In order to fall into the BH, the angular momentum must be taken away, which is a VERY hard task! Friction alone in an accretion disk does not do the job! You need other things. Jets are a possibility. So, a jet and highly relativistic particles streaming away from a black hole is natural and necessary. People have a hard time… Read more »
Aqua4U
Member
March 12, 2010 11:33 AM

Great to hear of worldwide co-operation of any sort!

Ahh So… model also represents the nucleus of an atom? or center of a star? or center of a globular cluster? or center of a galaxy? or center of? NOW I’m starting to see ….fractal cosmology?

solrey
Member
March 12, 2010 11:46 AM
1) NOTHING can exceed the speed of light. It’s really that simple. There is experimental evidence of superluminal speed. An ultrawideband electromagnetic pulse transmitter initiated by a picosecond laser In order to increase the energy of photoelectrons, a high-transparency metal mesh to which a voltage was applied was mounted near the reflector surface. Electrons accelerated in the interelectrode gap penetrate into the space behind the mesh anode, where they form a current pulse normal to the mesh surface. The front of the photoelectron current runs along the anode surface with faster-than-light (superluminal) speed and provides the in-phase summation of radiation fluxes from elementary sources. And this: Superluminal pulse transmission through a phase-conjugating mirror As for astrophysical jets, the… Read more »
Al Hall
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Al Hall
March 12, 2010 9:26 AM

DrFlimmer Says:
“1) NOTHING can exceed the speed of light. It’s really that simple.”

Are you positive? .. Perhaps the math is incomplete. Not saying it is, just saying “perhaps”.. E = mc² … smile

Excalibur
Member
Excalibur
March 12, 2010 11:06 AM

@Aodhan

Quote: “I’m going to speculate we cannot see/detect the gamma rays until they are so far out, because they are exceeding the speed of ligh

Cannot see/detect [the] gammarays until they are so far out ?? Something tells me you have a completely wrong idea about how electromagnetic fenomenon are detected. They are detected when they reach our detectors, the detectors here close to the earth, not close to the black hole…

DrFlimmer
Member
DrFlimmer
March 12, 2010 12:41 PM
@ Al Hall: Are you positive? Yes! For all we have seen, measured and checked, GR and SR are correct. @ solrey: About your quote/first link: As I see it, the pulse is maybe only faster than the speed of light in the air (which would also be superluminal). This would not be faster than the speed of light in vacuum. Such things have been observed quite often, and we use this effect to measure high-energy-radiation by their Cerenkov light emission (HESS e.g.). This is how interpret the first page of your source — more is not available to me. About your second link: A few lines down on the first page, one can read this: Here, we… Read more »
Hannes
Member
Hannes
March 12, 2010 1:34 PM
@DrFlimmer: You have excellent reasoning, but as long you do not know the nature of gravity and matter your conclusion: “People have a hard time believing this, because they think the particles come “out” of the black hole. This is not the case. The particles come from the accretion disk and are collimated into the jets.” .. might be faulty. Explain this: the earth is accelerating at 1 G since the beginning of her existance. Einstein’s Equivalence Principle shows that there is no difference between constant acceleration of a rocket and gravity. We are moving now compared to the beginning of a young Earth with a relative speed of 99,99999999E % lightspeed. We are a dangerous black hole… Read more »
Al Hall
Member
Al Hall
March 12, 2010 2:57 PM

DrFlimmer –

True, so true.. The math looks pretty solid based on what we know at the moment… And I stress “…on what we know at the moment..” smile

Lawrence B. Crowell
Member
Lawrence B. Crowell
March 12, 2010 5:47 PM

@ Aodhhan: From now on stop making flame comments. Your statement above about faster than light particles can only be replied to with a real “face palm” comment.

The event horizon does not causally influence the outside universe. In fact it is just the opposite.

The magneto-hydrodynamics of jets occurs from the huge heating of material falling onto a black hole. The nucleon and electron have different masses which results in charge separations. This is the source of currents and the whole MHD physics behind jets.

LC

DrFlimmer
Member
DrFlimmer
March 13, 2010 12:54 AM
@ Hannes: Yeah, Gedankenexperiments are a nice tool… Explain this: the earth is accelerating at 1 G since the beginning of her existance. […] We are moving now compared to the beginning of a young Earth with a relative speed of 99,99999999E % lightspeed. We are a dangerous black hole now if set back in time! Well, the earth would possibly move with the speed you said, but that is no problem. Maybe the earth would have gained enough mass due to its speed that for an external observer, the earth should have become a black hole. However, for a human being on the surface of the earth, the earth would still be like it ever was, because… Read more »
Al Hall
Member
Al Hall
March 13, 2010 1:12 AM

Hawking radiation…. or ….Black Hole Evaporation…. Another one that the LHC is supposed to “prove”…… Hmmm.,,. I don’t know…. Time will tell…

Hannes
Member
Hannes
March 13, 2010 1:55 AM
@DrFlimmer Jar Jar Binks was send with a rocket to space. He doesn’t know why, but he will do the job – testing the equivalence principle with a massive ball in his hand. He is in a big rocket with much fuel. He is accelerating with 1G . He also knows without looking out of a window that at the end of the trip there will be more mass in the ceiling than below him. Jar Jar drops the ball. Will it drop to the ceiling or on his foot? His brother Einstein look to the ship and sees the ceiling has more mass. Jar jar Binks is afraid he will hurt his feet. What will Einstein say?… Read more »
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