- Astronomers measured the light hitting Earth from outside our galaxy
- Over a very broad wavelength range – from a fraction of a micron to mm
- A fraction of the photons come from other galaxies and the Big Bang
- Radiation from outside the galaxy is so small there is no need for alarm
Abigail Beall For Mailonline
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This summer you might be spending some time topping up your tan on the beach, basking in the warmth and light from our sun.
But the light that helps cause tans, and sun burn, does not only come from our sun.
Small fractions of the light that hits your skin having travelled across the universe for billions of years, a new study has found.
For the first time, astronomers have accurately measured the light hitting the Earthfrom outside our galaxy over a very broad wavelength range – from a fraction of a micron (damaging) to millimetres (harmless)
WHERE YOUR SUN TAN COMES FROM
1,000,000,000,000,000,000,000 photons per square metre per second come from the sun.
300,000,000,000,000,000,000 photons per square metre per second are reflected off the sky.
10,000,000,000,000,000 photons per square metre per second are left over from the Big Bang.
100,000,000,000,000 photons per square metre per second are reflected off dust in the solar system.
10,000,000,000 photons per square metre per second are from extra-galactic background light.
Your body will be bombarded by about sextillion photons of light per second.
Most of these photons, or small packets of energy, originate from the sun.
But a very small fraction have travelled across the universe for billions of years before ending their existence when they collide with your skin.
For the first time, astronomers have accurately measured the light hitting the Earth from outside our galaxy over a very broad wavelength range – from a fraction of a micron, which is damaging, to millimetres, which is harmless.
But radiation from outside the galaxy is so small there is no immediate need for alarm.
International Centre for Radio Astronomy Research (ICRAR) astrophysicist Professor Simon Driver said we are constantly bombarded by about 10 billion photons per second from intergalactic space when we’re outside, day and night.
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This summer you might be spending some time topping up your tan on the beach, basking in the warmth and light from our sun. But the light that helps cause tans, and sun burn, does not only come from our sun
HOW THE STUDY WAS DONE
For the first time, astronomers have accurately measured the light hitting the Earth from outside our galaxy over a very broad wavelength range – from a fraction of a micron, which is damaging, to millimetres, which is harmless.
Lead author Professor Driver, based at the University of Western Australia, measured this ambient radiation from the universe, from a wide range of wavelengths by combining deep images from a flotilla of space telescopes.
They found our bodies will be bombarded by about sextillion photons of light per second.
Most of these photons, or small packets of energy, originate from the sun.
But a very small fraction have travelled across the universe for billions of years before ending their existence when they collide with our skin.
‘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,’ Professor Driver said.
‘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.’
Lead author Professor Driver, based at the University of Western Australia, measured this ambient radiation from the universe, from a wide range of wavelengths by combining deep images from a flotilla of space telescopes.
While 10 billion photons a second might sound like a lot we would have to bask in it for trillions of years before it caused any long-lasting damage.
Professor Rogier Windhorst, from Arizona State University, added 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 universe 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
GALAXIES HAVE AN SPF TOO
While 10 billion photons a second might sound like a lot we would have to bask in it for trillions of years before it caused any long-lasting damage.
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, the researchers say.
He said: ‘The galaxies themselves provide us with a natural suntan lotion with an SPF of about two.’
The study is part of ICRAR’s ongoing work to understand the evolution of energy, mass and structure in the universe.
The research programme examines how we went from the smooth distribution of atoms in the early universe to the emergence of the Periodic Table and the multitude of stars, galaxies and galaxy clusters we see today.
‘The processes which shape and shuffle mass generate vast quantities of energy, dwarfed only by the vastness of space,’ Professor Driver said.
‘The precise physics as to how this energy is released is still not fully understood and work continues to build numerical models capable of explaining the energy that we’ve now measured.’
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