Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Physicist probes dark, violent side of the universe; studies highest energy photons

29.10.2002


In search of cosmic mayhem


The Whipple Observatory gamma-ray telescope



A physicist at Washington University in St. Louis working with scientists at the Smithsonian Institution is unveiling the dark, violent side of the universe.

Studying the highest energy photons known to science, Washington University Associate Professor of Physics James H. Buckley, Ph.D., and his colleagues are analyzing bursts of gamma rays released from massive black holes at the center of so-called active galaxies.


Using the Whipple Observatory gamma-ray telescope and camera in the Santa Rita Mountains, south of Tucson, the Whipple collaboration, of which Buckley is a member, first discovered astronomical sources of terra-electron volt (TeV) from the Crab Nebula. Like meteor showers, each TeV photon leaves a faint blue streak in the atmosphere that points back to its source. Over the last decade, they also have discovered six occurrences of energetic gamma-ray flares from peculiar galaxies known as Active galaxies or Blazars. "We are learning about the physical conditions inside what are known as relativistic jets, which produce TeV gamma rays, " said Buckley. "The jets are composed of matter and radiation that move very close to the speed of light, scattering ambient light up to extremely high (TeV) energies.

"Just this June (2002), we discovered enormous flares of TeV gamma rays from an object called 1 ES 1959+650 that lasted for hours. The flares were incredibly rapid, signifying a very compact emission region, consistent with the Black Hole hypothesis."

In addition to unveiling the nature of the monster that lies at the center of these enigmatic galaxies, the technique of TeV gamma-ray astronomy also holds promise to reveal the nature of the "dark matter" that comprises the majority of our own galaxy.

It is estimated that less than 10 % of the matter in the universe is ordinary matter such as protons, neutrons and electrons. The rest is composed of two dark components: About 30% of the universe appears to be composed of "dark matter" and another 65 % of some new form of "dark energy." While these two components dominate the mass budget for the universe, their nature is unknown.

"It is widely believed that cold dark matter formed the first structure in the universe, and that galaxies subsequently formed by falling into the gravitational potential wells formed by the dark matter," Buckley explained. "A dark matter halo with a very high central density should exist in our own galaxy. Favored models for this dark matter predict that annihilation of the dark matter particles should result in monochromatic gamma-ray emission in the energy range 0.1 TeV to 8 TeV. "

Buckley said that planned experiments may well have the sensitivity to detect this new component of the universe.

Over the last half century new windows on the invisible universe were opened with radio, and x-ray astronomy. In just the last decade, the universe has been revealed in a new, even more extreme form of radiation, terra-electron volt (TeV) gamma rays. These photons are so energetic that no terrestrial particle accelerator can produce them.

A TeV photon has the same energy as an electron accelerated by a trillion volts. While there are no sources of such photons on the Earth, TeV gamma rays appear to be produced by an ever-increasing number of astrophysical sources.

The Whipple Observatory gamma-ray telescope is a 10-meter reflector that images the faint flashes of blue light from the showers of energetic particles produced as individual gamma-ray photons interact in the Earth’s atmosphere.

When an energetic gamma ray interacts in the atmosphere it produces an electron and a positron (the electron’s antiparticle). These go on to liberate more electrons and gamma rays and other matter. An avalanche called an electromagnetic cascade ensues. The particles in this "shower" are moving so rapidly that they emit an electromagnetic shock wave known as Cherenkov radiation, much like a sonic boom emitted by a supersonic jet.

A fast camera on the Whipple telescope takes 20 nanosecond snapshots of the streaks of light produced by each photon. Collectively, these streaks of Cherenkov light point back to the object much like lines of perspective converge at the distant horizon. Buckley and his colleagues analyze these images in detail and produce a picture of the sky at terra-electron volt energies.

One of the most exciting discoveries by the Whipple group is the TeV emission from active galactic nuclei, or AGNs. In these remarkable galaxies, a compact nucleus can outshine the rest of the galaxy by a factor of as much as 100 or 1000. The optical luminosity of the compact central object exceeds what could be produced by thermonuclear fusion, and is believed to result from the accretion of mass into the deep gravitational potential well of a supermassive black hole.

"Measurements of matter swirling around the central objects point to the existence of black holes with the mass of hundreds of millions of suns," said Buckley. "In many of these sources radio observations reveal jet- like outflows presumably aligned with the rotation axis of the central black hole. The TeV gamma-ray measurements have been used to provide a quantitative measure of the speed of these relativistic outflows, which appear to be traveling as much as 99.98 percent of the speed of light."

Questions

Contact: Tony Fitzpatrick, senior science editor, Washington University in St. Louis, 314-935-5272; tony_fitzpatrick@aismail.wustl.edu; or Gerry Everding, University Communications, 314-935-6375; gerry_everding@aismail.wustl.edu.

Gerry Everding | EurekAlert!
Further information:
http://www.wustl.edu/

More articles from Physics and Astronomy:

nachricht Further Improvement of Qubit Lifetime for Quantum Computers
09.12.2016 | Forschungszentrum Jülich

nachricht Electron highway inside crystal
09.12.2016 | Julius-Maximilians-Universität Würzburg

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: Electron highway inside crystal

Physicists of the University of Würzburg have made an astonishing discovery in a specific type of topological insulators. The effect is due to the structure of the materials used. The researchers have now published their work in the journal Science.

Topological insulators are currently the hot topic in physics according to the newspaper Neue Zürcher Zeitung. Only a few weeks ago, their importance was...

Im Focus: Significantly more productivity in USP lasers

In recent years, lasers with ultrashort pulses (USP) down to the femtosecond range have become established on an industrial scale. They could advance some applications with the much-lauded “cold ablation” – if that meant they would then achieve more throughput. A new generation of process engineering that will address this issue in particular will be discussed at the “4th UKP Workshop – Ultrafast Laser Technology” in April 2017.

Even back in the 1990s, scientists were comparing materials processing with nanosecond, picosecond and femtosesecond pulses. The result was surprising:...

Im Focus: Shape matters when light meets atom

Mapping the interaction of a single atom with a single photon may inform design of quantum devices

Have you ever wondered how you see the world? Vision is about photons of light, which are packets of energy, interacting with the atoms or molecules in what...

Im Focus: Novel silicon etching technique crafts 3-D gradient refractive index micro-optics

A multi-institutional research collaboration has created a novel approach for fabricating three-dimensional micro-optics through the shape-defined formation of porous silicon (PSi), with broad impacts in integrated optoelectronics, imaging, and photovoltaics.

Working with colleagues at Stanford and The Dow Chemical Company, researchers at the University of Illinois at Urbana-Champaign fabricated 3-D birefringent...

Im Focus: Quantum Particles Form Droplets

In experiments with magnetic atoms conducted at extremely low temperatures, scientists have demonstrated a unique phase of matter: The atoms form a new type of quantum liquid or quantum droplet state. These so called quantum droplets may preserve their form in absence of external confinement because of quantum effects. The joint team of experimental physicists from Innsbruck and theoretical physicists from Hannover report on their findings in the journal Physical Review X.

“Our Quantum droplets are in the gas phase but they still drop like a rock,” explains experimental physicist Francesca Ferlaino when talking about the...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

ICTM Conference 2017: Production technology for turbomachine manufacturing of the future

16.11.2016 | Event News

Innovation Day Laser Technology – Laser Additive Manufacturing

01.11.2016 | Event News

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

14.10.2016 | Event News

 
Latest News

Researchers identify potentially druggable mutant p53 proteins that promote cancer growth

09.12.2016 | Life Sciences

Scientists produce a new roadmap for guiding development & conservation in the Amazon

09.12.2016 | Ecology, The Environment and Conservation

Satellites, airport visibility readings shed light on troops' exposure to air pollution

09.12.2016 | Health and Medicine

VideoLinks
B2B-VideoLinks
More VideoLinks >>>