Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:


Extreme Jets Take New Shape

Jets of particles streaming from black holes in far-away galaxies operate differently than previously thought, according to a study published today in Nature.

The new study reveals that most of the jet's light—gamma rays, the universe's most energetic form of light—is created much farther from the black hole than expected and suggests a more complex shape for the jet.

The research was led by scientists at the Kavli Institute for Particle Astrophysics and Cosmology, jointly located at the Department of Energy's SLAC National Accelerator Laboratory and Stanford University, with participation from scientists from around the world. The study included data from more than 20 telescopes including the Fermi Gamma-ray Space Telescope and KANATA telescope.

High above the flat Milky Way galaxy, bright galaxies called blazars dominate the gamma-ray sky, discrete spots on the dark backdrop of the universe. As nearby matter falls into the 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.

"As the universe's biggest accelerators, blazar jets are important to understand," said KIPAC Research Fellow Masaaki Hayashida, who serves as corresponding author on the paper 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."

Researchers had previously theorized that such jets are held together by strong magnetic field tendrils, while the jet's light is created by particles revolving 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."

Locating the Gamma Rays
Over a full year of observations, the researchers focused on one particular blazar jet, located in the constellation Virgo, monitoring it in many different wavelengths of light: gamma-ray, X-ray, optical, infrared and radio. Blazars continuously flicker, and researchers expected continual changes in all types of light. 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 rays with an equal mix of all polarizations or directionality—the extreme bending of energetic particles around a magnetic field line can polarize light. During the 20-day gamma-ray flare, optical light streaming from the jet changed its polarization. This temporal connection between changes in the gamma-ray light and changes in the optical light suggests that both types of light are created in the same geographical region of the jet; during those 20 days, something in the local environment altered 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 energy escapes a black hole. 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."

Rethinking Jet Structure
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.

The gamma-ray observations used in this study were made by the Large Area Telescope on board the Fermi Gamma-ray Space Telescope, an astrophysics and particle physics partnership developed by NASA in collaboration with the U.S. Department of Energy Office of Science, along with important contributions from academic institutions and partners in France, Germany, Italy, Japan, Sweden, and the United States. LAT collaboration members were key participants in the development of this research. SLAC National Accelerator Laboratory managed construction of the LAT and now plays the central role in science operations, data processing and making scientific data available to collaborators for analysis.

The optical polarization data that played a crucial role in this study was taken by the KANATA collaboration, using the KANATA telescope located in Higashihiroshima, Japan. The KANATA telescope is operated by Hiroshima University.

The GASP-WEBT observatories participating in this work are Abastumani, Calar Alto, Campo Imperatore, Crimean, Kitt Peak (MDM), L'Ampolla, Lowell (Perkins-PRISM), Lulin, Roque de los Muchachos (KVA and Liverpool), San Pedro Ma´rtir, St Petersburg for the optical–NIR bands, and Mauna Kea (SMA),Medicina, Metsahovi, Noto and UMRAO for the millimeter radio band.

The campaign also included data from NASA satellites Swift and the ROSSI X-ray Timing Explorer, and the Japanese satellite Suzaku.

Melinda Lee | EurekAlert!
Further information:

More articles from Physics and Astronomy:

nachricht Move over, lasers: Scientists can now create holograms from neutrons, too
21.10.2016 | National Institute of Standards and Technology (NIST)

nachricht Finding the lightest superdeformed triaxial atomic nucleus
20.10.2016 | The Henryk Niewodniczanski Institute of Nuclear Physics Polish Academy of Sciences

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: New 3-D wiring technique brings scalable quantum computers closer to reality

Researchers from the Institute for Quantum Computing (IQC) at the University of Waterloo led the development of a new extensible wiring technique capable of controlling superconducting quantum bits, representing a significant step towards to the realization of a scalable quantum computer.

"The quantum socket is a wiring method that uses three-dimensional wires based on spring-loaded pins to address individual qubits," said Jeremy Béjanin, a PhD...

Im Focus: Scientists develop a semiconductor nanocomposite material that moves in response to light

In a paper in Scientific Reports, a research team at Worcester Polytechnic Institute describes a novel light-activated phenomenon that could become the basis for applications as diverse as microscopic robotic grippers and more efficient solar cells.

A research team at Worcester Polytechnic Institute (WPI) has developed a revolutionary, light-activated semiconductor nanocomposite material that can be used...

Im Focus: Diamonds aren't forever: Sandia, Harvard team create first quantum computer bridge

By forcefully embedding two silicon atoms in a diamond matrix, Sandia researchers have demonstrated for the first time on a single chip all the components needed to create a quantum bridge to link quantum computers together.

"People have already built small quantum computers," says Sandia researcher Ryan Camacho. "Maybe the first useful one won't be a single giant quantum computer...

Im Focus: New Products - Highlights of COMPAMED 2016

COMPAMED has become the leading international marketplace for suppliers of medical manufacturing. The trade fair, which takes place every November and is co-located to MEDICA in Dusseldorf, has been steadily growing over the past years and shows that medical technology remains a rapidly growing market.

In 2016, the joint pavilion by the IVAM Microtechnology Network, the Product Market “High-tech for Medical Devices”, will be located in Hall 8a again and will...

Im Focus: Ultra-thin ferroelectric material for next-generation electronics

'Ferroelectric' materials can switch between different states of electrical polarization in response to an external electric field. This flexibility means they show promise for many applications, for example in electronic devices and computer memory. Current ferroelectric materials are highly valued for their thermal and chemical stability and rapid electro-mechanical responses, but creating a material that is scalable down to the tiny sizes needed for technologies like silicon-based semiconductors (Si-based CMOS) has proven challenging.

Now, Hiroshi Funakubo and co-workers at the Tokyo Institute of Technology, in collaboration with researchers across Japan, have conducted experiments to...

All Focus news of the innovation-report >>>



Event News

#IC2S2: When Social Science meets Computer Science - GESIS will host the IC2S2 conference 2017

14.10.2016 | Event News

Agricultural Trade Developments and Potentials in Central Asia and the South Caucasus

14.10.2016 | Event News

World Health Summit – Day Three: A Call to Action

12.10.2016 | Event News

Latest News

Resolving the mystery of preeclampsia

21.10.2016 | Health and Medicine

Stanford researchers create new special-purpose computer that may someday save us billions

21.10.2016 | Information Technology

From ancient fossils to future cars

21.10.2016 | Materials Sciences

More VideoLinks >>>