A DISH of magnetic oil could prove a cheap and simple way to sharpen fuzzy images of far-away objects.
Unlike telescopes in space, ground-based telescopes have to view the heavens through the Earth鈥檚 atmosphere, which distorts the light from distant objects. This explains why stars twinkle.
To improve fuzzy images, astronomers usually find a well-characterised star in the region of space they are looking at. Because they know what this star should look like, they can use it to measure how much the light is being blurred as it travels through the atmosphere and then correct for the effect.
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Usually this is done using a computer that controls an array of tiny piezoelectric actuators fitted to the back of a thin glass mirror. The actuators gently bend and twist the mirror to the required position, so that when the blurred image is bounced off the mirror the reflected image is much sharper. Because the atmosphere is constantly changing, the shape of the mirror must also change rapidly 鈥� around 100 times each second.
But such 鈥渁daptive-optics鈥� mirrors are costly 鈥� up to $45,000 for one measuring less than 4 centimetres across. Now, Ermanno Borra and his team of physicists at Laval University in Quebec, Canada, have found a cheaper way to make mirrors that could sharpen even the most badly blurred image. First they floated a film of shiny silver nanoparticles on top of a millimetre-thick layer of oil containing millions of tiny magnetic particles. Then, to make their 鈥渕irror鈥� change shape, Borra sat it on a base containing hundreds of electric coils. Passing currents through the coils set up magnetic fields that pulled and pushed at the magnetic particles, dragging the oil with them. This in turn forced the reflective surface into a complex range of hills and valleys tens of micrometres high.
Borra is now working with researchers at the National Institute of Optics in Quebec to commercialise a mirror within the year. He estimates the cost will be about one tenth that of existing mirrors. Borra says large mirrors, more than a metre wide, would also be easy to build. Equipped with such mirrors, the next generation of 鈥渆xtremely large telescopes鈥� might be able to see planets orbiting distant stars.
Paul Hickson, an astronomer at the State University of New York at Stony Brook, told 快猫短视频 that at the moment Borra鈥檚 mirror is only reflective enough at certain wavelengths of light. 鈥淭hey need to improve the reflectivity, but what they鈥檝e done already is really quite remarkable,鈥� he says.
