Ten Trillionths Of Your Suntan Comes From Beyond Our Galaxy

At the beach, your body is bombarded by about sextillion photons of light per second, but don’t worry, you will have to bask in it for trillions of years before it causes any long-lasting damage.

AsianScientist (Aug. 17, 2016) – Astronomers in Australia have accurately measured the light hitting the Earth from outside our galaxy over a very broad wavelength range. Their work was published in the Astrophysical Journal.

The research looked at photons, whose wavelengths vary from a fraction of a micron (damaging) to millimeters (harmless). Most of these photons, or small packets of energy, originate from the Sun. But a very small fraction have traveled across the Universe for billions of years before ending their existence when they collide with your skin.

Fortunately, radiation from outside the galaxy constitutes only ten trillionths of your suntan, so there is no immediate need for alarm.

International Center for Radio Astronomy Research astrophysicist Professor Simon Driver, who led the study, said we are constantly bombarded by about ten billion photons per second from intergalactic space when we’re outside, day and night. While ten billion might sound like a lot, Driver said we would have to bask in it for trillions of years before it caused any long-lasting damage.

Ten trillionths of a suntan comes from beyond our galaxy. Credit: ICRAR
Ten trillionths of a suntan comes from beyond our galaxy. Credit: ICRAR

The international research team led by Driver accurately measured this ambient radiation from the Universe and from a wide range of wavelengths, by combining deep images from space telescopes.

Professor Rogier Windhorst from Arizona State University said the Universe also comes with its own inbuilt protection, as about half the energy coming from the ultraviolet light of galaxies is converted into a less damaging wavelength by dust grains.

“The galaxies themselves provide us with a natural suntan lotion with an SPF of about two,” Windhorst said.

The article can be found at: Driver et al. (2016) Extra-galactic Background Light Measurements from the Far-UV to the Far-IR from Deep Ground and Space-based Galaxy Counts.


Source: International Center for Radio Astronomy Research; Photo: Shutterstock.
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