Sun tanning comes almost universally from the Sun. However, a small proportion comes from other sources of ultraviolet light. This light is produced from nearby stars and radiation from other galaxies, some of it dating back to the ‘Big Bang.’
This amount of ultraviolet light penetrating the Earth’s atmosphere is very small. From other stars, the ultraviolet light level amounts to less than one-billionth of one percent. The contribution from the photons dating back to the Big Bang are estimated to contribute about 0.001 percent.
These findings come from Professor Simon Driver, who is employed at the University of Western Australia in Crawley. The figures are based on complex calculations.
According to Science News, Professor Driver undertook the assessment as part of on-going research to understand the level of extragalactic background light. This light accounts for a diffuse glow through the universe. The diffuse extragalactic background light is all the accumulated radiation in the universe due to star formation processes. The light covers the ultraviolet, optical, and infrared regions of the electromagnetic spectrum.
The new calculations were derived at from multiple telescopes. Not only could they estimate the proportion of ultraviolet light from other sources, the researchers were able to pinpoint the type of photons (covering the spectrum from infrared to ultraviolet). A photon is an elementary particle, the quantum of all forms of electromagnetic radiation including light.
With this it was found that some 50 percent of the photons originated with the formation of galaxy cores and supermassive black holes during roughly the first four billion years of the history of the universe.
The findings are published in the Astrophysical Journal. The research paper is titled “Measurements of extragalactic background light from the far-UV to the far-IR from deep ground- and space-based galaxy counts.”
