Enjoy basking in the sun? Some of that light is coming from outside our galaxy

A new study has found that the sun reaching us has travelled across the universe for billions of years. REUTERS/Nacho Doce

Have you laid outside to catch the warm rays of the sun this summer? It turns out that some of the light that hits your body is coming from far beyond our sun and far beyond our galaxy.

In a new paper to be published in the Astrophysical Journal on August 12, astronomers claim to have accurately measured light that has reached Earth from outside our galaxy.

Light has the unique ability to be both a particle (photon) and a wave. In order to calculate how much light is extra-galactic, the researchers examined the varying wavelengths of photons: those that are just a fraction of a micron, which is considered to be damaging, to those that are millimetres, which are considered to be damaging.

They concluded that our bodies are hit with about 10 billion photons per second from intergalactic space. But there’s no need to worry: it’s only about ten trillionth of your suntan.

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10 trillionths of a suntan comes from beyond our galaxy.
10 trillionths of a suntan comes from beyond our galaxy. ICRAR/Dan Hutton

“Most of the photons of light hitting us originate from the sun, whether directly, scattered by the sky, or reflected off dust in the solar system,” said International Centre for Radio Astronomy Research (ICRAR) astrophysicist Professor Simon Driver, who led the study. “However, we’re also bathed in radiation from beyond our galaxy, called the extra-galactic background light.

“These photons are minted in the cores of stars in distant galaxies, and from matter as it spirals into supermassive black holes.”

In order for any damage to be done to us from this intergalactic light, we’d have to bathe in it for trillions of years, according to Driver.

And our universe actually provides us with some protection: dust grains convert the damaging ultraviolet waves from other galaxies into less damaging wavelengths.

“The galaxies themselves provide us with a natural suntan lotion with an SPF of about two,” said Rogier Windhorst, from Arizona State University who also worked on the study.

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The goal of the research wasn’t to figure out how much of our suntan comes from the great beyond, but rather to help astronomers better understand energy and the structure of our universe.

But still: now you can claim that your suntan isn’t just out of this world, but out of this galaxy.

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