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Very high energy gamma rays from a distant Quasar: How transparent is the Universe?

MAGIC discovers the most distant very-high energy gamma-ray emission from an accreting supermassive black hole.

The MAGIC (Major Atmospheric Gamma-ray Imaging Cherenkov) telescope has detected emission of very high energy gamma rays from the active nucleus of the 3C279 galaxy. The quasar's distance is more than five billion light years (roughly half the radius of the Universe) from the Earth, more than twice the distance of objects previously observed with this kind of radiation.

3C279 is a prominent member of the class of active galactic nuclei (AGNs) containing super-massive black holes, typically a billion times more massive than the Sun, powered by accreting matter from surrounding stars or gas. AGNs emit radiation across the entire electromagnetic spectrum from radio wavelengths to very high energy (VHE) gamma-rays. Whereas most of the emission can travel through the Universe without being absorbed, the flux of VHE gamma rays is attenuated by pair-production in interactions with low energy photons of the extragalactic background light (EBL). The EBL comprises the history of all light produced by stars and galaxies in the Universe and is, therefore, of great interest as a record of cosmological structure formation. The detection of VHE gamma-ray emission from a source at such a distance as 3C279 constrains current theories about the density of the EBL. The Universe appears more transparent at cosmological distances than believed, precluding significant contributions from light other than from sources observed by current optical and infrared telescopes.

The MAGIC result confirms once more the rich potential of gamma-ray observations to open new avenues in astronomy. Gamma rays constitute the highest-energy electromagnetic radiation observable, and are generated by the most violent cosmic objects such as supernovae, active galactic nuclei, and gamma ray bursts. They allow us to zoom into a realm of extreme physical conditions, far beyond what can be studied in terrestrial laboratories. Gamma rays are highly important messengers in modern astroparticle physics and astronomy: they provide precious information about the processes that generated them, without deflections by magnetic fields that affect all charged Cosmic Rays. Since such particles travel for distances comparable with the radius of the Universe, they also give important information on fundamental physics and cosmology, in particular about the evolution of the Universe.

Background Information on the MAGIC Telescope

MAGIC is a gamma-ray telescope with a mirror of 17m diameter, the largest stand-alone telescope worldwide. It was built and is operated by a large international collaboration, including currently about 150 researchers from Germany, Italy, Spain, Switzerland, Poland, Finland, Bulgaria and the United States. It is located at the Roque de los Muchachos Observatory, on the Canary island of La Palma. It detects gamma rays through short light flashes that are produced when gamma rays cross the atmosphere (Cherenkov light). A second MAGIC telescope is under construction close to the first, and will be inaugurated in September 2008.

Background Information on 3C279

3C279 was one of the brightest quasars seen by the EGRET instrument on board NASA's Compton Gamma-Ray Observatory.


Picture courtesy APOD, EGRET team, Compton Observatory, NASA

Like all quasars, 3C279 is a nondescript, faint, starlike object in the visible sky. Yet, in June of 1991 a gamma-ray telescope onboard NASA's orbiting Compton Gamma-Ray Observatory unexpectedly discovered that it was one of the brightest objects in the gamma-ray sky. Shortly after this image was recorded, the quasar faded from view at gamma-ray energies. Astronomers are still trying to understand what causes these enigmatic objects to flare so violently. Another quasar, 3C273, is faintly visible above and to the right of center.

Original Publication: MAGIC Collaboration, "Very high energy gamma rays from a distant Quasar: How transparent is the Universe?", Science, Vol. 320, 1752 (Abstract).

Shortly after sunset MAGIC atop Roque de los Muchachos on the Canary Island of La Palma is preparing for the nightly observations.



Sky Map of 3C279 in Very-High Energy photons as seen by MAGIC. The active galactic nucleus, from which these photons originated, is a quasar distant more than five billion light years from the Earth.



While the first MAGIC telescope is successfully taking data since 2004, a second telescope, further increasing the instrument's sensitivity, is under construction and will be inaugurated in September 2008.

The MAGIC telescope has detected very high energy photons from the active galactic nucleus of the galaxy 3C279, a quasar distant more than five billion light years from the Earth. The detection of very-high energy gamma emission by a source at such a distance challenges current theories about the intergalactic medium, which appears more transparent than previously believed.

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This page was created by Robert Wagner. Last modification 05.01.2009 by Robert Wagner.
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