Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

In The Heart Of Cygnus, NASA's Fermi Reveals A Cosmic-ray Cocoon

29.11.2011
The constellation Cygnus, now visible in the western sky as twilight deepens after sunset, hosts one of our galaxy's richest-known stellar construction zones. Astronomers viewing the region at visible wavelengths see only hints of this spectacular activity thanks to a veil of nearby dust clouds forming the Great Rift, a dark lane that splits the Milky Way, a faint band of light marking our galaxy's central plane.

Located in the vicinity of the second-magnitude star Gamma Cygni, the star-forming region was named Cygnus X when it was discovered as a diffuse radio source by surveys in the 1950s. Now, a study using data from NASA's Fermi Gamma-ray Space Telescope finds that the tumult of star birth and death in Cygnus X has managed to corral fast-moving particles called cosmic rays.

Cosmic rays are subatomic particles -- mainly protons -- that move through space at nearly the speed of light. In their journey across the galaxy, the particles are deflected by magnetic fields, which scramble their paths and make it impossible to backtrack the particles to their sources.

Yet when cosmic rays collide with interstellar gas, they produce gamma rays -- the most energetic and penetrating form of light -- that travel to us straight from the source. By tracing gamma-ray signals throughout the galaxy, Fermi's Large Area Telescope (LAT) is helping astronomers understand the sources of cosmic rays and how they're accelerated to such high speeds. In fact, this is one of the mission's key goals.

The galaxy's best candidate sites for cosmic-ray acceleration are the rapidly expanding shells of ionized gas and magnetic field associated with supernova explosions. For stars, mass is destiny, and the most massive ones -- known as types O and B -- live fast and die young.

They're also relatively rare because such extreme stars, with masses more than 40 times that of our sun and surface temperatures eight times hotter, exert tremendous influence on their surroundings. With intense ultraviolet radiation and powerful outflows known as stellar winds, the most massive stars rapidly disperse their natal gas clouds, naturally limiting the number of massive stars in any given region.

Which brings us back to Cygnus X. Located about 4,500 light-years away, this star factory is believed to contain enough raw material to make two million stars like our sun. Within it are many young star clusters and several sprawling groups of related O- and B-type stars, called OB associations. One, called Cygnus OB2, contains 65 O stars -- the most massive, luminous and hottest type -- and nearly 500 B stars.

Astronomers estimate that the association's total stellar mass is 30,000 times that of our sun, making Cygnus OB2 the largest object of its type within 6,500 light-years. And with ages of less than 5 million years, few of its most massive stars have lived long enough to exhaust their fuel and explode as supernovae.

Intense light and outflows from the monster stars in Cygnus OB2 and from several other nearby associations and star clusters have excavated vast amounts of gas from their vicinities. The stars reside within cavities filled with hot, thin gas surrounded by ridges of cool, dense gas where stars are now forming. It's within the hollowed-out zones that Fermi's LAT detects intense gamma-ray emission, according to a paper describing the findings that was published in the Nov. 25 edition of the journal Science.

"We are seeing young cosmic rays, with energies comparable to those produced by the most powerful particle accelerators on Earth. They have just started their galactic voyage, zig-zagging away from their accelerator and producing gamma rays when striking gas or starlight in the cavities," said co-author Luigi Tibaldo, a physicist at Padova University and the Italian National Institute of Nuclear Physics.

The energy of the gamma-ray emission, which is measured up to 100 billion electron volts by the LAT and even higher by ground-based gamma-ray detectors, indicates the extreme nature of the accelerated particles. (For comparison, the energy of visible light is between 2 and 3 electron volts.) The environment holds onto its cosmic rays despite their high energies by entangling them in turbulent magnetic fields created by the combined outflows of the region's numerous high-mass stars.

"These shockwaves stir the gas and twist and tangle the magnetic field in a cosmic-scale jacuzzi so the young cosmic rays, freshly ejected from their accelerators, remain trapped in this turmoil until they can leak into quieter interstellar regions, where they can stream more freely," said co-author Isabelle Grenier, an astrophysicist at Paris Diderot University and the Atomic Energy Commission in Saclay, France.

The well known Gamma Cygni supernova remnant – so named for its proximity to the star -- also lies within this region; astronomers estimate its age at about 7,000 years. The Fermi team considers it possible that the supernova remnant spawned the cosmic rays trapped in the Cygnus X "cocoon," but they also suggest an alternative scenario where the particles became accelerated through repeated interaction with shockwaves produced inside the cocoon by powerful stellar winds.

"Whether the particles further gain or lose energy inside this cocoon needs to be investigated, but its existence shows that cosmic-ray history is much more eventful than a random walk away from their sources," Tibaldo added.

Fermi is providing a never-before-seen glimpse of the early life of cosmic rays, long before they diffuse into the galaxy at large. Astronomers know of a dozen stellar clusters at least as young and rich as Cygnus OB2, including the Arches and Quintuplet clusters near the galaxy's center. Energetic gamma rays are detected in the vicinity of several of them, so perhaps they also corral cosmic rays in their own high-energy cocoons.

NASA's Fermi is an astrophysics and particle physics partnership managed by NASA's Goddard Space Flight Center in Greenbelt, Md., and developed in collaboration with the U.S. Department of Energy, with important contributions from academic institutions and partners in France, Germany, Italy, Japan, Sweden and the United States.

Related Links:

Nursery of Giants Captured in New Spitzer Image
http://www.nasa.gov/vision/universe/starsgalaxies/spitzer-041304.html
NASA's Fermi Telescope Detects Gamma-Rays From 'Star Factories' in Other Galaxies

http://www.nasa.gov/mission_pages/GLAST/news/star_factories.html

What is Cygnus X?
http://www.cfa.harvard.edu/cygnusX/whatis.html
Francis Reddy
NASA's Goddard Space Flight Center, Greenbelt, Md.

Francis Reddy | EurekAlert!
Further information:
http://www.nasa.gov
http://www.nasa.gov/mission_pages/GLAST/news/cygnus-cocoon.html

More articles from Physics and Astronomy:

nachricht Electrocatalysis can advance green transition
23.01.2017 | Technical University of Denmark

nachricht Quantum optical sensor for the first time tested in space – with a laser system from Berlin
23.01.2017 | Ferdinand-Braun-Institut Leibniz-Institut für Höchstfrequenztechnik

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: Quantum optical sensor for the first time tested in space – with a laser system from Berlin

For the first time ever, a cloud of ultra-cold atoms has been successfully created in space on board of a sounding rocket. The MAIUS mission demonstrates that quantum optical sensors can be operated even in harsh environments like space – a prerequi-site for finding answers to the most challenging questions of fundamental physics and an important innovation driver for everyday applications.

According to Albert Einstein's Equivalence Principle, all bodies are accelerated at the same rate by the Earth's gravity, regardless of their properties. This...

Im Focus: Traffic jam in empty space

New success for Konstanz physicists in studying the quantum vacuum

An important step towards a completely new experimental access to quantum physics has been made at University of Konstanz. The team of scientists headed by...

Im Focus: How gut bacteria can make us ill

HZI researchers decipher infection mechanisms of Yersinia and immune responses of the host

Yersiniae cause severe intestinal infections. Studies using Yersinia pseudotuberculosis as a model organism aim to elucidate the infection mechanisms of these...

Im Focus: Interfacial Superconductivity: Magnetic and superconducting order revealed simultaneously

Researchers from the University of Hamburg in Germany, in collaboration with colleagues from the University of Aarhus in Denmark, have synthesized a new superconducting material by growing a few layers of an antiferromagnetic transition-metal chalcogenide on a bismuth-based topological insulator, both being non-superconducting materials.

While superconductivity and magnetism are generally believed to be mutually exclusive, surprisingly, in this new material, superconducting correlations...

Im Focus: Studying fundamental particles in materials

Laser-driving of semimetals allows creating novel quasiparticle states within condensed matter systems and switching between different states on ultrafast time scales

Studying properties of fundamental particles in condensed matter systems is a promising approach to quantum field theory. Quasiparticles offer the opportunity...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Sustainable Water use in Agriculture in Eastern Europe and Central Asia

19.01.2017 | Event News

12V, 48V, high-voltage – trends in E/E automotive architecture

10.01.2017 | Event News

2nd Conference on Non-Textual Information on 10 and 11 May 2017 in Hannover

09.01.2017 | Event News

 
Latest News

Tracking movement of immune cells identifies key first steps in inflammatory arthritis

23.01.2017 | Health and Medicine

Electrocatalysis can advance green transition

23.01.2017 | Physics and Astronomy

New technology for mass-production of complex molded composite components

23.01.2017 | Process Engineering

VideoLinks
B2B-VideoLinks
More VideoLinks >>>