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This is a post by Jansen Penido for the Young Astronomers.

The LBT (Large Binocular Telescope) is an optical/infrared telescope placed at the Mount Graham International Observatory, in Arizona, USA. It is a partnership among several institutes from Italy, Germany and USA.

The Large Binocular Telescope Observatory in Mt. Graham. Credit: John Hill

Different from most telescopes, LBT has two primary mirrors, measuring 8.4 meters (27 ft) wide, each mounted in the same enclosure (whence the name “binocular”). Together, they can capture the same amount of light as an 11.8 meter (39 ft) wide ‘standard’ telescope. What’s more: by combining the light from the two mirrors, the LBT is able to achieve the image clarity of a 22.8 meter (75 ft) aperture. In other words, this telescope delivers an image quality far greater than that of the Hubble Space Telescope (at certain wavelengths.



What’s the secret?

The secret of LBT lies in the coherent combination of the light collected by both mirrors, a technique that scientists call

The two primary mirrors are mounted with a 14.4 meter center-center separation. Credit: Marc-Andre Besel and Wiphu Rujopakarn

interferometry. By setting the mirrors far apart, astronomers can take two images, merge them together and improve the resolution of the resultant picture; as if had been produced by a large mirror the size of the distance between the actual mirrors. This is done with the help of an instrument called LBTI (Large Binocular Telescope Interferometer).

LBTI is also able to help the astronomers analyse the images. A special system was designed to explore young stars – surrounded by disks of gas and dust that may eventually evolve to planetary systems – and even to detect planets around them – observing the infra-red light to see through the cloud that obscures visible light.

Pros and cons of ground-based telescopes

During the last several years, the majority of astronomical discoveries have been made using space telescopes. In fact, the telescopes in orbit have a privileged vision of the cosmos, since they’re not subjected to the atmospheric turbulence and light/thermal interference. Moreover, some wavelengths of light, like x-rays, are filtered by our atmosphere and can’t be detected from the ground. Though supporting an observatory in space implies a high cost with production, launch, operation and maintenance.

With the most recent technological advancements, scientists have created ways to increase the clarity of the images by passing the light through a system to compensate for the blur of the Earth’s atmosphere. Such systems are called adaptive optics. The LBT’s instrument FLAO (First Light Adaptive Optics) is responsible for ‘fixing’ the atmospheric blurring, allowing the telescope to literally see as clearly as if there was no atmosphere above it.

A true-color image of Messier 1, the Crab Nebula, taken by LBT. This famous nebula is located in our own galaxy at a distance of about 6300 light years from Earth. Credit: LBT

“This is an incredibly exciting time as this new adaptive optics system allows us to achieve our potential as the world’s most powerful optical telescope,”

said Richard Green, director of the LBT, just after the installation of FLAO.

So the LBT represents a remarkable step forward for astronomy, bringing us the next generation of ground-based telescopes, which will help us to better understand everything from the formation of planets around young stars in Milky Way to the biggest mysteries of the early universe.

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