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This is a stellar shot for more than one title. The photo above shows a cluster of stars 5,500 light-years away from the Earth, filled with fully ripe celestial bodies that are still growing.
This image is false color, which means that the same extent would be looked at naked eye very different from its current representation. Colors represent light in infrared wavelengths, which is impossible for humans to see. The snapshot of the star cluster, called RCW 38, is one of the sharpest and deepest images ever taken from the region. And it's not that they've caught this particular training on a good day of hair (or rather good corona). An image like this requires excellent photographic equipment, and this image is no exception.
Koraljka Muzic, a researcher at the University of Lisbon in Portugal, is leading the project. His team used the Very Large Telescope in Chile to locate the group of stars. She also used the camera-pronounced HAWK-I hawkeye, and it might be surprising to hear that it's a bit more advanced than your DSLR. HAWK-I is an abbreviation for the K-band Imager with a large, high-acuity field. It was installed in 2007 and was already very good for taking pictures of distant celestial objects. But recently, scientists have installed an upgrade called GRAAL. And this upgrade involves lasers.
Even for a powerful camera like HAWK-I, there are limits to being a ground-based telescope. Namely, the sky. Of course, the atmosphere around us allows us to breathe, protects us from a lot of solar radiation, and generally plays a huge role in life here on Earth. But the man is bad to look at the sky.
"The atmosphere is turbulent and blurs our images," says Muzic. Even on a clear night, atmospheric disturbances can disturb the astronomical views of stars, blurring and twisting the subject of their photography session. The changing winds and currents, the changes in temperature and density, all play in the choppy air between a telescope and a perfect view of the sky. These disturbances are the reason why the stars seem to flicker, even on a clear night.
GRAAL is working to counter this turbulence by using a technology called adaptive optics. "Adaptive optics has a real-time calculator that calculates the effect of turbulence on the wavelength," Muzic says. The computer determines how much turbulence deforms the image, and then sends this information to a deformable ceramic mirror, just two millimeters (0.08 inches) thick and 1.1 meters (3.6 feet) wide. The thin mirror has 170 actuators behind it, which can push the mirror slightly, doing exactly the opposite of what the chopped sky does above. It can adjust these actuators at a rate of about 800 times per second, following the changes in the air itself.
"This allows us to get much sharper images than with adaptive optics," says Muzic. This image was part of the scientific tests of the new HAWK-I system, GRAAL. It will open soon to more research opportunities.
In order to make all these small adjustments fast, GRAAL needs a reference point. "For Adaptive Optics to work, it needs a bright star in or near your object. But there are not many bright stars." in the sky, "says Muzic. Fortunately, there is an alternative. "Another way is to create an artificial star using lasers," she adds.
GRAAL has four lasers pointing upwards in the atmosphere. In the upper section, each of these lasers excites sodium atoms, creating a glow bright enough to emulate the stars. A VLT computer can compare what lasers are ideally supposed to look like with the turbulent way they actually appear and make their corrections fast, making the image sharper and sharper.
First proposal in 1953 decades that technology has progressed to the point where adaptive optical systems could be installed in telescopes around the world. Researchers have developed deformable mirrors, such as those used in the VLT, liquid mirrors controlled by magnetic fields, adaptive optical technologies adapted to make more advanced microscopes, and yes, captured beautiful images.
But it's not the aesthetic images they can take that make them so valuable to researchers like Muzic.
With the picture came back a lot of data. The main research interest of Muzic is the brown dwarfs, objects with characteristics somewhere between a big planet and a small star. They have been spotted in nearby star clusters, but Muzic hopes to find some of these faint objects in RCW 38, a more distant cluster of stars that does not have the same environment as some of the closest cluster. She is currently badyzing the data to see if these weak objects are present in the image.
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