There is a special sub-variety of life-bearing gas giant that is particularly rare, and interesting: they glow green. Bright green. Radioactive, fluorescent green, bright enough to be seen from space. They are the Glowing Green Giants (GGGs).

One can speculate about the cause. As this fluorescent green colouration only ever occurs on life-bearing worlds, the presence of life must be a causal factor. But since the vast majority of life-bearing worlds are not fluorescent green in colour, it is not merely the presence of microscopic airborne lifeforms that is the causal factor. Unfortunately, the numbers of such worlds that have been fully documented is still staggeringly low: only five of then have been reported on publicly-available sources to date. Further examples will be required for any statistically significant study as to the collective origins of this peculiar phenomenon.

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