It a characteristic of atoms that they can absorb and radiate only certain fixed frequencies of the electromagnetic spectrum. This then allows scientists to identify hydrogen in space even when the hydrogen is a billion light years away.
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The image above is an example of absorption banding in the spectrum. If energy is absorbed the area is black, and if energy passes right through, the area is not black. As an example of ‘energy passing right through’ you can consider radio frequency waves of energy, that pass right through walls and into your radio or television set. You can also consider absorption, in that your skin allows radio wave frequencies to pass right on through, but your skin absorbs UVA and UVB, which is why you get sun burned by those frequencies of electromagnetic radiation. If someone were to do a spectrum analysis of you they would find dark areas where the UVA and UVB would be, because those did not pass through your body. This is why you wear sun block, for the idea is that the sun block also absorbs UVA and UVB so that your skin doesn’t have to.
It is also typical for atoms to only emit certain fixed frequencies of electromagnetic energy when an atom releases energy. Hydrogen can only release three different frequencies, and those values are fixed, so if you saw those three skinny lines on an otherwise black chart, you would know that this was characteristic of the emission band of hydrogen.
It is also typical of atoms to only radiate energy in fixed quantities, with the amount radiated dependant upon the frequency of the energy being emitted. The measurement of this small amount of energy when measured in joules, is a very small number, a zero followed by a decimal point, followed by a long list of zeroes followed by a very small number.
Now when the black hole that created the Crab Nebula exploded, the Chinese astronomers reported that the light glowed so intensely that it was visible even in broad daylight for several years. How can we explain such intense brilliance for such an extended period.
We assume that it was a black hole that exploded, and further the Unified Field Theory of gravitation states that hyper-energetic atoms are trapped within black holes, and can only escape the black hole when the magnetic field of the black hole collapses. This could happen when the balance of free energy employed to maintain current flow becomes less than the expansion energy of trapped atoms, such that there could be different sizes of black holes and therefore they could have shorter or longer lives, depending upon the ratio of free energy to trapped atoms within each black hole.
Now when hyper-energetic atoms escape a black hole, they are free to radiate excess energy, for they no longer experience the crushing pressures of that black hole. However atoms are not free to radiate energy in any form, but only in discrete, fixed forms, and just a little at a time. Therefore we can know that it was energetic atoms which emerged within the region now called the Crab Nebula, and we know that those atoms were hyper-energetic, for the glow that lasted for years was caused by atoms losing an enormous amount of excess energy, while following the rules and releasing energy only at little bit at a time, a process which took several years.