Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:


Cosmic ray mystery solved?

Universe's most energetic particles point to huge black holes

The most energetic particles in the universe – ultrahigh-energy cosmic rays – likely come from supermassive black holes in the hearts of nearby active galaxies, says a study by scientists from nearly 90 research institutions worldwide, including the University of Utah.

“We discovered the sources of the highest energy particles in the universe,” says Miguel Mostafa, an assistant professor of physics at the University of Utah and one of 370 scientists and engineers belonging to a 17-nation collaboration that operates the $54 million Pierre Auger Observatory in Argentina.

“The sources are the center regions of very active galaxies which host violent black holes” and are known as “active galactic nuclei,” he adds. “Now that we found the sources, we are one step closer to knowing what physical process can accelerate particles to these ultrahigh energies. Right now, we don’t know.”

The study by the Pierre Auger Collaboration is being published in the Friday, Nov. 9 issue of the journal Science. Members of the collaboration at the University of Utah are Mostafa; physicist and Dean of Science Pierre Sokolsky; postdoctoral research associate Patrick Younk; and physics graduate student David Thomas. Two undergraduate students – Joshua Schmeiser and Felix Lau – also work on the project.

Black holes are collapsed stars with gravity so strong that nothing – not even light – can escape once it has fallen past the black hole’s “event horizon.” Scientists believe most galaxies, including ours, host supermassive black holes, which contain the mass of up to a few billion stars like our sun.

When matter is sucked into supermassive black holes, the process also spews out various particles and electromagnetic radiation, from gamma and X-rays to ultraviolet, visible and infrared light, and radio waves. A galaxy with a compact center that is extremely, persistently bright in all or some wavelengths is known as an active galactic nucleus (AGN). Only a fraction of galaxies with supermassive black holes are AGNs.

From the Fly’s Eye to the Auger Observatory

Cosmic rays, discovered in 1912, are subatomic particles, including nuclei of atoms such as hydrogen, oxygen, carbon, nitrogen or iron. Medium-energy cosmic rays come from exploding stars. The sun and other stars emit lower-energy cosmic rays. The source of ultrahigh-energy cosmic rays has been unexplained. They are 100 million times more energetic than anything produced by the most powerful particle smashers on Earth.

Suspected sources have included not only supermassive black holes in active galactic nuclei, but also noisy radio galaxies, shock waves from colliding galaxies, and bizarre sources such as so-called cosmic strings or the decay of massive particles left over from the “big bang” that scientists believe formed the universe 13 billion years ago.

The highest-energy cosmic ray ever detected was measured in 1991 by the University of Utah’s Fly’s Eye observatory on the U.S. Army’s Dugway Proving Ground. It had an energy of 300 billion billion electron volts (billion twice is correct, or 3 times 10 to the 20th power electron volts). The single subatomic particle would feel like a fast-pitched baseball if it could penetrate the atmosphere and hit a person in the head.

In 1996, an international group of physicists proposed building the Pierre Auger Project: twin $50 million cosmic ray observatories in Argentina and Utah. (Auger was a French physicist who, in 1938, discovered “air showers” of particles produced when incoming cosmic rays hit gas in Earth’s upper atmosphere.) The Argentina observatory was built first to look for cosmic rays in southern skies. The Northern Hemisphere observatory now is planned for Colorado.

Construction in Argentina started in 1999. The Auger Observatory – the world’s largest cosmic ray observatory – began collecting data in 2004. The observatory includes a 1,200-square-mile grid of 1,600 large, instrumented water tanks – which detect particles from air showers – and four sites with a total of 24 telescopes that detect faint fluorescent flashes in the sky caused when a cosmic ray particle triggers an air shower.

The Study: Ultrahigh-energy Cosmic Rays Correlate with Active Galaxies

In the study in Science, the Auger collaboration reports the observatory has recorded 77 cosmic rays with ultrahigh-energies above 40 billion billion electron volts (billion twice is correct, or 4 times 10 to the 19th power electron volts).

Of the 27 most energetic events – those with energies above 57 billion billion electron volts – 20 come from the direction of the known locations of some of the 318 active galactic nuclei with the Auger Observatory’s field of view, Mostafa says.

If the cosmic rays were coming randomly from all directions, only five or six would correlate with the known locations of the active galaxies, he adds.

The researchers report there is less than a one-in-100 chance that the correlation between ultrahigh-energy cosmic rays and active galactic nuclei is random, not real.

Mostafa says the galaxies spewing super-energetic cosmic rays must be relatively close to our Milky Way galaxy, within a distance of 100 megaparsecs, which works out to 326 million light years or 1,920 billion billion miles. (Billion twice is correct).

“This is our local neighborhood in cosmic terms,” he says.

Most ultrahigh-energy cosmic rays from greater distances would lose energy before they reach Earth because they interact with cosmic microwave background radiation – the “afterglow” of the “big bang.”

The University of Utah’s Contributions

Mostafa’s group at the University of Utah played a key role in designing, building and operating two lasers and four lidar (light detection and ranging) devices to monitor dust, clouds, water vapor and other atmospheric conditions above the Auger Observatory.

The devices ensure the accuracy of the fluorescence telescopes by helping scientists determine how much light is generated by a cosmic ray air shower, and how much that light is enhanced when it scatters off dust and vapor in the atmosphere.

Mostafa’s group also developed the “geometrical reconstruction technique” to analyze “hybrid” data from Auger’s tank-like particle detectors and florescence-detecting telescopes. The computer software uses that data to provide more precise information on the direction in space from which an incoming ultrahigh-energy cosmic ray originated.

Mostafa’s geometrical reconstruction method also will help physicists learn more about the specific process responsible for hurling ultrahigh-energy cosmic rays across space. While the black holes are thought to accelerate cosmic rays, another kind of theory holds that the highest-energy cosmic rays are photons – light particles – produced by the decay of superheavy particles left over from the birth of the universe. Mostafa’s method shows there are few if any photons with energy levels consistent with such theories.

The University of Utah is a pioneer in cosmic ray research. After atmospheric humidity stymied a 1950s effort to observe cosmic rays from upstate New York, University of Utah physicists built a prototype in New Mexico in 1976, constructed the Fly’s Eye at Dugway Proving Ground during 1980-1981, improved it in 1986, and then upgraded it during 1994-1999 and renamed it the High-Resolution Fly’s Eye. The name comes from the use of fly-like multifaceted mirrors to observe the sky.

The Hi-Res Fly’s Eye is shutting down and some of its equipment is being moved to the new $17 million Telescope Array cosmic ray observatory, which was built west of Delta, Utah, by the University of Tokyo and University of Utah.

Meanwhile, Mostafa’s group is responsible for designing the fluorescence detectors at the planned northern Auger Observatory in southeast Colorado near Lamar.

Lee Siegel | EurekAlert!
Further information:

More articles from Physics and Astronomy:

nachricht Mars 2020 mission to use smart methods to seek signs of past life
17.08.2017 | Goldschmidt Conference

nachricht Gold shines through properties of nano biosensors
17.08.2017 | American Institute of Physics

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: Fizzy soda water could be key to clean manufacture of flat wonder material: Graphene

Whether you call it effervescent, fizzy, or sparkling, carbonated water is making a comeback as a beverage. Aside from quenching thirst, researchers at the University of Illinois at Urbana-Champaign have discovered a new use for these "bubbly" concoctions that will have major impact on the manufacturer of the world's thinnest, flattest, and one most useful materials -- graphene.

As graphene's popularity grows as an advanced "wonder" material, the speed and quality at which it can be manufactured will be paramount. With that in mind,...

Im Focus: Exotic quantum states made from light: Physicists create optical “wells” for a super-photon

Physicists at the University of Bonn have managed to create optical hollows and more complex patterns into which the light of a Bose-Einstein condensate flows. The creation of such highly low-loss structures for light is a prerequisite for complex light circuits, such as for quantum information processing for a new generation of computers. The researchers are now presenting their results in the journal Nature Photonics.

Light particles (photons) occur as tiny, indivisible portions. Many thousands of these light portions can be merged to form a single super-photon if they are...

Im Focus: Circular RNA linked to brain function

For the first time, scientists have shown that circular RNA is linked to brain function. When a RNA molecule called Cdr1as was deleted from the genome of mice, the animals had problems filtering out unnecessary information – like patients suffering from neuropsychiatric disorders.

While hundreds of circular RNAs (circRNAs) are abundant in mammalian brains, one big question has remained unanswered: What are they actually good for? In the...

Im Focus: RAVAN CubeSat measures Earth's outgoing energy

An experimental small satellite has successfully collected and delivered data on a key measurement for predicting changes in Earth's climate.

The Radiometer Assessment using Vertically Aligned Nanotubes (RAVAN) CubeSat was launched into low-Earth orbit on Nov. 11, 2016, in order to test new...

Im Focus: Scientists shine new light on the “other high temperature superconductor”

A study led by scientists of the Max Planck Institute for the Structure and Dynamics of Matter (MPSD) at the Center for Free-Electron Laser Science in Hamburg presents evidence of the coexistence of superconductivity and “charge-density-waves” in compounds of the poorly-studied family of bismuthates. This observation opens up new perspectives for a deeper understanding of the phenomenon of high-temperature superconductivity, a topic which is at the core of condensed matter research since more than 30 years. The paper by Nicoletti et al has been published in the PNAS.

Since the beginning of the 20th century, superconductivity had been observed in some metals at temperatures only a few degrees above the absolute zero (minus...

All Focus news of the innovation-report >>>



Event News

Call for Papers – ICNFT 2018, 5th International Conference on New Forming Technology

16.08.2017 | Event News

Sustainability is the business model of tomorrow

04.08.2017 | Event News

Clash of Realities 2017: Registration now open. International Conference at TH Köln

26.07.2017 | Event News

Latest News

Gold shines through properties of nano biosensors

17.08.2017 | Physics and Astronomy

Greenland ice flow likely to speed up: New data assert glaciers move over sediment, which gets more slippery as it gets wetter

17.08.2017 | Earth Sciences

Mars 2020 mission to use smart methods to seek signs of past life

17.08.2017 | Physics and Astronomy

More VideoLinks >>>