Signals from another galaxy
Using a network of state-of-the-art telescopes, an international team of researchers has just detected three sources of very high-energy gamma rays in another galaxy. This is a first that may shed light on the origin of mysterious cosmic rays.
Three sources of gamma-ray radiation in the Large Magellanic Cloud, a satellite galaxy of the Milky Way: this is what the telescopes at the HESS Observatory have just detected. This is no ordinary discovery, as it is the first time these phenomena have been detected beyond our galaxy. These messages from the past (170,000 years ago) could tell us a great deal…
Invisible to the human eye
Gamma rays?“Concentrated bursts of energy. A trillion times more energetic than visible light, these ‘grains of light’ lie beyond the X-ray spectrum, in a wavelength range invisible to the human eye,” explains Matthieu Renaud, an astrophysicist at the Universe and Particles Laboratory in Montpellier.
To detect them, therefore, very specialized instruments are required.“As they enter Earth’s atmosphere, these gamma rays emit a very faint flash of bluish light (Cherenkov light) that the cameras on the HESS experiment’s telescopes are capable of detecting.” Located in Namibia, this network of four 13-meter-diameter telescopes, recently supplemented by a massive 28-meter telescope, is one of the most sensitive gamma-ray detection instruments in the world.
Mysterious cosmic radiation
The reason this discovery has experts so excited is that observing these rare phenomena will likely tell us a little more about the origin of “cosmic radiation”—that stream of particles that seems to be present everywhere in the universe and in which the Earth is constantly immersed.
A particularly stubborn mystery: discovered in 1912 by the Austrian physicist Victor Franz Hess, these extraterrestrial particles still haven’t revealed where they came from…
“We may be able to find out thanks to gamma rays. They are the best witnesses to extreme events in the universe: supernovae and their remnants, or pulsars and their wind nebulae, resulting from the evolution of massive stars. They are very good suspects in our investigation into the origin of cosmic radiation,”explains Matthieu Renaud.
New Horizons for Astronomy
A pulsar nebula, a supernova remnant, and a “superbubble” (a structure formed by the powerful winds of massive stars and their supernova explosions): these are the sources of the gamma-ray emissions that have just been observed with HESS.
About ten years ago, only a handful of very high-energy gamma-ray sources were known to exist in the vast expanse of the sky. Today, more than a hundred have been identified, thanks to gamma-ray telescopes such as HESS II—the largest of its kind—which have recently opened up a new window for astronomical observation.
