These are the so-called gamma-rays. Astronomers and physicists measure the energies of these photons of light in terms of MeV. 1 MeV, or 1 million electron volts, is about 1 million times more energetic than the photons of light we see with. A single gamma-ray photon with 1 MeV carries an energy equal to 0.0000016 ergs, which is an almost measurable pulse of energy by conventional laboratory standards.
The most energetic gamma-rays are studied by using the earth's atmosphere as a detector of what are called 'air showers'. When such a photon collides with an atom in the atmosphere, it unleashes a cascade of nuclear particles, electrons and anti-electrons which reach down to the ground in a triangular cone. As seen from the ground, this event would appear as a very faint burst or light covering a large fraction of the sky. Special telescopes have been built to search for these faint pulses. One of these is the so-called 'Fisheye' telescope. They are sensitive to gamma rays with an energy of 1,000,000,000 MeV; yes that's right 1000 million, million electron volts!!! Many of these events have been seen over the last few decades since people began looking for them in the sky. It is hard to imagine a single photon of light carrying 1600 ergs of energy. But they arrive about one air shower each second!
For more information, see the feature article in Sky and Telescope for May, 1990 page 479 where such a telescope in the antarctic is described.
Isn't nature grand?