The discovery of mysterious gamma-ray bursters in the late 1960s opened up a new chapter in astronomy. Now gamma-ray astronomy has taken another surprising turn with the revelation that many of the previously unidentified high-energy gamma-ray sources in our galaxy, the Milky Way, comprise a whole new class of mysterious objects that “shine” continuously instead of coming in bursts.
The known gamma-ray universe contains many yet-unidentified gamma-ray sources, listed in a 271-source catalogue compiled by the Energetic Gamma Ray Telescope Experiment aboard NASA’s Compton Gamma Ray Observatory spacecraft. Scientists have struggled to associate these unidentified sources with known objects emitting other types of light.
Of the unidentified gamma sources in our galaxy, about half lie in a narrow band along the galactic plane. These may be well known classes of objects that simply shine too faintly in other types of light to be identified – gamma rays pass through intervening material much more easily than other types of radiation.
The other half of the unidentified galactic gamma sources – the new class – are closer to Earth. These lie just off the Milky Way plane and seemingly follow the Gould Belt – a ribbon of nearby massive stars and gas clouds that winds through the Milky Way plane. However the mechanisms of powerful gamma-ray emitters, whether in bursts or more prolonged, remains a mystery.
