Distant galaxies appear to be flashing 鈥撀燽ut this is actually an optical illusion caused by changes in Earth鈥檚 atmosphere that could be both a blessing and a curse for astronomers.
Mark Kuiack at the University of Amsterdam in the Netherlands and his colleagues were using the Amsterdam-ASTRON Radio Transient Facility And Analysis Center to search for flares of radio light from distant objects throughout the universe, but they found something a little closer to home. Sometimes, a known source of radio light, like a galaxy, would unexpectedly flash up to 100 times brighter for around 20 seconds.
A closer look at the flashes showed that these bursts of light weren鈥檛 actually intrinsic to the distant galaxies, but rather an effect of Earth鈥檚 atmosphere. The top layer of the atmosphere is constantly bombarded with photons from the sun, which cause ripples and fluctuations in the density of the air there, bending the distant light.
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鈥淭hese little turbulent eddies and density fluctuations form different shapes,鈥� says Kuiack. 鈥淲hen there鈥檚 a little region that is much less dense than the area around it, it can be sort of a natural lens that stacks on top of your telescope lens.鈥� When that natural lens passes between an observer and a distant object, it can make the object appear to flash.
That could be a problem for astronomical surveys looking for different types of cosmic events that emit radio waves, Kuiack says. In fact, he and his team have already identified one apparent astronomical discovery that seems to be actually a flash in the atmosphere.
However, he says, if used carefully this effect could also be helpful. 鈥淭his phenomenon can take sources which are usually too dim for us to see and magnify them to the extent that we can observe them,鈥� he says. If we can characterise the atmospheric eddies more precisely, we could potentially use them to help us spot more distant, dim objects in space.
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