High energy cosmic rays may be released during commonly occurring stellar explosions. The discovery suggests these explosions can sometimes be more powerful than we believed, and might give us a better idea of how they occur.
Galactic cosmic rays 鈥� particles that move at close to the speed of light 鈥� are nearly always accompanied by very high energy gamma radiation. This co-occurrence is helpful because cosmic rays are deflected by magnetic fields before they reach Earth, making it difficult to work out where they came from. But the gamma radiation isn鈥檛 deflected, so it is easier to establish its source 鈥� and hence also the source of the cosmic rays.
聽at Heidelberg University in Germany and his colleagues have been studying such gamma rays using the聽聽鈥� a global system of telescopes.
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On the , used by researchers to communicate new findings rapidly, Wagner鈥檚 team report the discovery of extremely high energy gamma radiation coming from a single source called RS Ophiuchi in the constellation Ophiuchus, about 5000 light years away from Earth.
RS Ophiuchi consists of a white dwarf and a red giant, and the white dwarf temporarily brightens in a聽鈥渘ova鈥� explosion聽about once every 15 to 20 years.聽A closer look suggests the high energy gamma radiation was released during one of these nova explosions.
Novas are a lot smaller than supernova explosions 鈥� which happen when a star dies 鈥� but the new discovery suggests that some nova explosions may be far stronger than we believed. The radiation released during the nova in Ophiuchus was between 10 to 100 times stronger than that associated with any nova previously studied.
鈥淲e鈥檝e looked at nova outbursts for the last few years and never seen high energy gamma radiation,鈥� says Wagner. 鈥淭his is the first detection.鈥�
Wagner says the particles, along with the radiation released, will give us a better idea of what happens inside a nova explosion.
at Columbia University says it is an important finding, though he notes that most high energy cosmic rays are still likely to come from supernovas. He also says it is unclear whether this means that other novas also release cosmic rays, or if this nova is just special.
鈥淲e need to get lucky to catch more gamma-ray bright classical novae to address this question in the future,鈥� he says.
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