Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Laser beams help take the twinkle out of starlight

04.06.2002


If you have ever peered down a highway on a sunny day, you have probably seen the rising, wavelike ripples of heated air that distort the appearance of objects near the horizon. Similar disturbances in the atmosphere above us make stars twinkle as their light is distorted on the way down to Earth.



Although twinkling stars inspired a well-known nursery rhyme, the effect hampers astronomers’ attempts to study the heavens. Scientists at Lawrence Livermore National Laboratory are now building systems, known as a synthetic guide stars, to help astronomers accurately account for atmospheric distortions wherever they choose to point their telescopes. Pictures collected by large terrestrial telescopes equipped with such systems often exceed the quality of Hubble Space Telescope images.

Guide stars have long played an important role in correcting atmospheric distortion. Astronomers pick a bright, stable star near a region of the sky that they hope to study and monitor distortions in the guide star image to deduce the optical properties of the atmosphere. They then correct their images with adaptive optics, which distort telescope components to offset atmospherically induced errors. Generally, adaptive optics corrections involve warping light-collecting telescope mirrors with computer controlled motors that respond to changes in the guide star image.


Guide stars and adaptive optics combine to provide stunning pictures of planets, galaxies, and other objects. Unfortunately, astronomers find suitable natural guide stars in only one percent of the sky. At the 2002 Conference on Lasers and Electro-Optics/Quantum Electronics and Laser Science Conference (May 19-23, www.cleoconference.org) meeting in Long Beach, CA, Deanna Pennington explained that she and her colleagues at Lawrence Livermore National Laboratory have now opened up a much larger portion of the heavens with a manmade analog to guide stars. Pennington estimates that the synthetic guide star system can correct for atmospheric turbulence in about three fifths of the sky.

The researchers create their synthetic guide star by beaming a laser through the atmosphere in the direction of an object they wish to study. The frequency of the laser is specifically chosen to excite sodium atoms, causing them to emit yellow light. Sodium is relatively scarce in most of our atmosphere, but incoming meteors deposit a concentrated layer of the atoms in the mesosphere, about ninety kilometers above the earth. The laser paints an artificial star in the sky when it strikes the sodium rich layer.

Pennington points out that natural stars are best for correcting atmospheric distortion. Stars are so far away that they appear to be point light sources effectively located at infinity. Synthetic guide stars, in comparison, are too close to completely eliminate atmospheric errors, but they provide astronomers with seventy-five percent of the benefit offered by natural guide stars.

Any telescope equipped with adaptive optics can benefit from the addition of a synthetic guide star system, but the technology will be indispensable for future, earth-based observations. "Very large telescopes," says Pennington," must use adaptive optics to approach their theoretical performance. Atmospheric turbulence primarily dictates the ultimate resolution a telescope can achieve." Telescope designs being considered for future observatories may sport mirrors thirty to a hundred meters across, and will dwarf even cutting-edge telescopes such as the ten-meter telescope at Keck Observatory in Hawaii. Larger telescopes collect more light and could provide ever high resolution images, provided we correct for the hazy blanket of gas that surrounds our planet.

Although the Keck telescope already uses adaptive optics that rely on natural guide stars, Pennington’s group installed a new sodium guide star system at the observatory last year. Keck’s adaptive optics successfully locked on to the laser-generated guide star in tests performed last December, but modifications to the system interfaces prevented astronomers from using it to collect images. If the final installation stages go as planned, a synthetic guide star shining over Hawaii should help astronomers peer into the heavens by Christmas 2002.

For more information contact:

Deanna Pennington pennington1@llnl.gov
Lawrence Livermore National Laboratory
P.O. Box 5500, L-477
Livermore, CA 94551
925-423-9234


James Riordon | EurekAlert

More articles from Physics and Astronomy:

nachricht Researchers create artificial materials atom-by-atom
28.03.2017 | Aalto University

nachricht Astronomers probe swirling particles in halo of starburst galaxy
28.03.2017 | International Centre for Radio Astronomy Research

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: A Challenging European Research Project to Develop New Tiny Microscopes

The Institute of Semiconductor Technology and the Institute of Physical and Theoretical Chemistry, both members of the Laboratory for Emerging Nanometrology (LENA), at Technische Universität Braunschweig are partners in a new European research project entitled ChipScope, which aims to develop a completely new and extremely small optical microscope capable of observing the interior of living cells in real time. A consortium of 7 partners from 5 countries will tackle this issue with very ambitious objectives during a four-year research program.

To demonstrate the usefulness of this new scientific tool, at the end of the project the developed chip-sized microscope will be used to observe in real-time...

Im Focus: Giant Magnetic Fields in the Universe

Astronomers from Bonn and Tautenburg in Thuringia (Germany) used the 100-m radio telescope at Effelsberg to observe several galaxy clusters. At the edges of these large accumulations of dark matter, stellar systems (galaxies), hot gas, and charged particles, they found magnetic fields that are exceptionally ordered over distances of many million light years. This makes them the most extended magnetic fields in the universe known so far.

The results will be published on March 22 in the journal „Astronomy & Astrophysics“.

Galaxy clusters are the largest gravitationally bound structures in the universe. With a typical extent of about 10 million light years, i.e. 100 times the...

Im Focus: Tracing down linear ubiquitination

Researchers at the Goethe University Frankfurt, together with partners from the University of Tübingen in Germany and Queen Mary University as well as Francis Crick Institute from London (UK) have developed a novel technology to decipher the secret ubiquitin code.

Ubiquitin is a small protein that can be linked to other cellular proteins, thereby controlling and modulating their functions. The attachment occurs in many...

Im Focus: Perovskite edges can be tuned for optoelectronic performance

Layered 2D material improves efficiency for solar cells and LEDs

In the eternal search for next generation high-efficiency solar cells and LEDs, scientists at Los Alamos National Laboratory and their partners are creating...

Im Focus: Polymer-coated silicon nanosheets as alternative to graphene: A perfect team for nanoelectronics

Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are less stable. Now researchers at the Technical University of Munich (TUM) have, for the first time ever, produced a composite material combining silicon nanosheets and a polymer that is both UV-resistant and easy to process. This brings the scientists a significant step closer to industrial applications like flexible displays and photosensors.

Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

International Land Use Symposium ILUS 2017: Call for Abstracts and Registration open

20.03.2017 | Event News

CONNECT 2017: International congress on connective tissue

14.03.2017 | Event News

ICTM Conference: Turbine Construction between Big Data and Additive Manufacturing

07.03.2017 | Event News

 
Latest News

Researchers create artificial materials atom-by-atom

28.03.2017 | Physics and Astronomy

Researchers show p300 protein may suppress leukemia in MDS patients

28.03.2017 | Health and Medicine

Asian dust providing key nutrients for California's giant sequoias

28.03.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>