Forum für Wissenschaft, Industrie und Wirtschaft

Hauptsponsoren:     3M 
Datenbankrecherche:

 

NASA'S Fermi Proves Supernova Remnants Produce Cosmic Rays

15.02.2013
A new study using observations from NASA's Fermi Gamma-ray Space Telescope reveals the first clear-cut evidence the expanding debris of exploded stars produces some of the fastest-moving matter in the universe. This discovery is a major step toward understanding the origin of cosmic rays, one of Fermi's primary mission goals.

"Scientists have been trying to find the sources of high-energy cosmic rays since their discovery a century ago," said Elizabeth Hays, a member of the research team and Fermi deputy project scientist at NASA's Goddard Space Flight Center in Greenbelt, Md. "Now we have conclusive proof supernova remnants, long the prime suspects, really do accelerate cosmic rays to incredible speeds."

Cosmic rays are subatomic particles that move through space at almost the speed of light. About 90 percent of them are protons, with the remainder consisting of electrons and atomic nuclei. In their journey across the galaxy, the electrically charged particles are deflected by magnetic fields. This scrambles their paths and makes it impossible to trace their origins directly.

Through a variety of mechanisms, these speedy particles can lead to the emission of gamma rays, the most powerful form of light and a signal that travels to us directly from its sources.

Since its launch in 2008, Fermi's Large Area Telescope (LAT) has mapped million- to billion-electron-volt (MeV to GeV) gamma-rays from supernova remnants. For comparison, the energy of visible light is between 2 and 3 electron volts.

The Fermi results concern two particular supernova remnants, known as IC 443 and W44, which scientists studied to prove supernova remnants produce cosmic rays. IC 443 and W44 are expanding into cold, dense clouds of interstellar gas. These clouds emit gamma rays when struck by high-speed particles escaping the remnants.

Scientists previously could not determine which atomic particles are responsible for emissions from the interstellar gas clouds because cosmic ray protons and electrons give rise to gamma rays with similar energies. After analyzing four years of data, Fermi scientists see a distinguishable feature in the gamma-ray emission of both remnants. The feature is caused by a short-lived particle called a neutral pion, which is produced when cosmic ray protons smash into normal protons. The pion quickly decays into a pair of gamma rays, emission that exhibits a swift and characteristic decline at lower energies. The low-end cutoff acts as a fingerprint, providing clear proof that the culprits in IC 443 and W44 are protons.

The findings will appear in Friday's issue of the journal Science.

"The discovery is the smoking gun that these two supernova remnants are producing accelerated protons," said lead researcher Stefan Funk, an astrophysicist with the Kavli Institute for Particle Astrophysics and Cosmology at Stanford University in Calif. "Now we can work to better understand how they manage this feat and determine if the process is common to all remnants where we see gamma-ray emission."

In 1949, the Fermi telescope's namesake, physicist Enrico Fermi, suggested the highest-energy cosmic rays were accelerated in the magnetic fields of interstellar gas clouds. In the decades that followed, astronomers showed supernova remnants were the galaxy's best candidate sites for this process.

A charged particle trapped in a supernova remnant's magnetic field moves randomly throughout the field and occasionally crosses through the explosion's leading shock wave. Each round trip through the shock ramps up the particle's speed by about 1 percent. After many crossings, the particle obtains enough energy to break free and escape into the galaxy as a newborn cosmic ray.

The supernova remnant IC 443, popularly known as the Jellyfish Nebula, is located 5,000 light-years away toward the constellation Gemini and is thought to be about 10,000 years old. W44 lies about 9,500 light-years away toward the constellation Aquila and is estimated to be 20,000 years old. Each is the expanding shock wave and debris formed when a massive star exploded.

The Fermi discovery builds on a strong hint of neutral pion decay in W44 observed by the Italian Space Agency's AGILE gamma ray observatory and published in late 2011.

NASA's Fermi Gamma-ray Space Telescope is an astrophysics and particle physics partnership. Goddard manages Fermi. The telescope was developed in collaboration with the U.S. Department of Energy, with contributions from academic institutions and partners in the United States France, Germany, Italy, Japan, and Sweden.

For images and a video related to this finding, please visit:
http://go.nasa.gov/Yp14cJ
For more information about NASA's Fermi Gamma-ray Space Telescope and its mission, visit: http://www.nasa.gov/fermi

J.D. Harrington | EurekAlert!
Further information:
http://www.nasa.gov

More articles from Physics and Astronomy:

nachricht Telescopes team up to find distant Uranus-sized planet through microlensing
31.07.2015 | NASA/Goddard Space Flight Center

nachricht California 'rain debt' equal to average full year of precipitation
31.07.2015 | NASA/Goddard Space Flight Center

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: Gefangen in Ruhelosigkeit

Mit ultrakalten Atomen lässt sich ein neuer Materiezustand beobachten, in dem das System nicht ins thermische Gleichgewicht kommt.

Was passiert, wenn man kaltes und heißes Wasser mischt? Nach einer Weile ist das Wasser lauwarm – das System hat ein neues thermisches Gleichgewicht erreicht....

Im Focus: Quantum Matter Stuck in Unrest

Using ultracold atoms trapped in light crystals, scientists from the MPQ, LMU, and the Weizmann Institute observe a novel state of matter that never thermalizes.

What happens if one mixes cold and hot water? After some initial dynamics, one is left with lukewarm water—the system has thermalized to a new thermal...

Im Focus: Superschneller Wellenritt im Kristall: Elektronik auf Zeitskala einzelner Lichtschwingungen möglich

Physikern der Universitäten Regensburg und Marburg ist es gelungen, die von einem starken Lichtfeld getriebene Bewegung von Elektronen in einem Halbleiter in extremer Zeitlupe zu beobachten. Dabei konnten sie ein grundlegend neues Quantenphänomen entschlüsseln. Die Ergebnisse der Wissenschaftler sind jetzt in der renommierten Fachzeitschrift „Nature“ veröffentlicht worden (DOI: 10.1038/nature14652).

Die rasante Entwicklung in der Elektronik mit Taktraten bis in den Gigahertz-Bereich hat unser Alltagsleben revolutioniert. Sie stellt jedoch auch Forscher...

Im Focus: On the crest of the wave: Electronics on a time scale shorter than a cycle of light

Physicists from Regensburg and Marburg, Germany have succeeded in taking a slow-motion movie of speeding electrons in a solid driven by a strong light wave. In the process, they have unraveled a novel quantum phenomenon, which will be reported in the forthcoming edition of Nature.

The advent of ever faster electronics featuring clock rates up to the multiple-gigahertz range has revolutionized our day-to-day life. Researchers and...

Im Focus: Erster Nachweis von Lithium in einem explodierenden Stern

Erstmals konnte das chemische Element Lithium in der ausgestoßenen Materie einer Nova nachgewiesen werden. Beobachtungen von Nova Centauri 2013 mit Teleskopen des La Silla-Observatoriums der ESO und in der Nähe von Santiago de Chile helfen bei der Aufklärung des Rätsels, warum so viele junge Sterne mehr von diesem Element enthalten als erwartet. Diese Entdeckung liefert ein seit langem fehlendes Teil im Puzzle der chemischen Entwicklungsgeschichte unserer Galaxie und ist ein großer Fortschritt für das Verständnis des Mischungsverhältnisses der chemischen Elemente in den Sternen unserer Milchstraße.

Das leichte chemische Element Lithium ist eines der wenigen Elemente, das nach unserer Modellvorstellung auch beim Urknall vor 13,8 Milliarden Jahren...

Alle Focus-News des Innovations-reports >>>

Anzeige

Anzeige

IHR
JOB & KARRIERE
SERVICE
im innovations-report
in Kooperation mit academics
Veranstaltungen

Türme und Maste aus Stahl – Neues aus Forschung und Anwendung

31.07.2015 | Veranstaltungen

Tagung „Brandschutz im Tank- und Gefahrgutlager“ am 16. November 2015 im Essener Haus der Technik stellt praktische Lösungen vor

30.07.2015 | Veranstaltungen

12. BMBF-Forum für Nachhaltigkeit: Green Economy, Energiewende und die Zukunft der Städte

30.07.2015 | Veranstaltungen

 
B2B-VideoLinks
Weitere VideoLinks >>>
Aktuelle Beiträge

Wiederaufladbare Batterien machen sich breit

31.07.2015 | Seminare Workshops

Alles zur Kryotechnik: HDT bietet Seminar zum „Kryostatbau“ an

31.07.2015 | Seminare Workshops

Erster Zug von Siemens für Thameslink‑Strecke in UK angekommen

31.07.2015 | Verkehr Logistik