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 New quantum phenomena in graphene superlattices
19.09.2017 | Graphene Flagship

nachricht Solar wind impacts on giant 'space hurricanes' may affect satellite safety
19.09.2017 | Embry-Riddle Aeronautical University

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: Ultrafast snapshots of relaxing electrons in solids

Using ultrafast flashes of laser and x-ray radiation, scientists at the Max Planck Institute of Quantum Optics (Garching, Germany) took snapshots of the briefest electron motion inside a solid material to date. The electron motion lasted only 750 billionths of the billionth of a second before it fainted, setting a new record of human capability to capture ultrafast processes inside solids!

When x-rays shine onto solid materials or large molecules, an electron is pushed away from its original place near the nucleus of the atom, leaving a hole...

Im Focus: Quantum Sensors Decipher Magnetic Ordering in a New Semiconducting Material

For the first time, physicists have successfully imaged spiral magnetic ordering in a multiferroic material. These materials are considered highly promising candidates for future data storage media. The researchers were able to prove their findings using unique quantum sensors that were developed at Basel University and that can analyze electromagnetic fields on the nanometer scale. The results – obtained by scientists from the University of Basel’s Department of Physics, the Swiss Nanoscience Institute, the University of Montpellier and several laboratories from University Paris-Saclay – were recently published in the journal Nature.

Multiferroics are materials that simultaneously react to electric and magnetic fields. These two properties are rarely found together, and their combined...

Im Focus: Fast, convenient & standardized: New lab innovation for automated tissue engineering & drug

MBM ScienceBridge GmbH successfully negotiated a license agreement between University Medical Center Göttingen (UMG) and the biotech company Tissue Systems Holding GmbH about commercial use of a multi-well tissue plate for automated and reliable tissue engineering & drug testing.

MBM ScienceBridge GmbH successfully negotiated a license agreement between University Medical Center Göttingen (UMG) and the biotech company Tissue Systems...

Im Focus: Silencing bacteria

HZI researchers pave the way for new agents that render hospital pathogens mute

Pathogenic bacteria are becoming resistant to common antibiotics to an ever increasing degree. One of the most difficult germs is Pseudomonas aeruginosa, a...

Im Focus: Artificial Enzymes for Hydrogen Conversion

Scientists from the MPI for Chemical Energy Conversion report in the first issue of the new journal JOULE.

Cell Press has just released the first issue of Joule, a new journal dedicated to sustainable energy research. In this issue James Birrell, Olaf Rüdiger,...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

“Lasers in Composites Symposium” in Aachen – from Science to Application

19.09.2017 | Event News

I-ESA 2018 – Call for Papers

12.09.2017 | Event News

EMBO at Basel Life, a new conference on current and emerging life science research

06.09.2017 | Event News

 
Latest News

“Lasers in Composites Symposium” in Aachen – from Science to Application

19.09.2017 | Event News

New quantum phenomena in graphene superlattices

19.09.2017 | Physics and Astronomy

A simple additive to improve film quality

19.09.2017 | Power and Electrical Engineering

VideoLinks
B2B-VideoLinks
More VideoLinks >>>