Astronomers Are Creating “Fake Stars”, And It’s Changing What We Can See From Earth

Astronomers have always faced the fundamental challenge of observing the universe through the distortion of light as it passes through Earth's atmosphere when viewing the stars. They have been able to overcome this challenge with the help of the laser guide star technique, which enables astronomers to view the universe with greater clarity when using telescopes on the ground. The concept is quite simple: astronomers use high-powered lasers to illuminate the atmosphere with a beam of light, which then stimulates a layer of sodium atoms 90 to 100 kilometers above the Earth's surface. This leads to the creation of a bright spot of light, which is referred to as the “fake star.” Astronomers use the “fake star” to analyze the distortion of the light as it passes through the atmosphere. Adaptive optics is then used to correct the distortion hundreds or thousands of times per second with the help of a mirror.

This method is extremely useful in improving the clarity of the image. “Laser guide stars make it possible to approach the level of sharpness which is typically associated with space telescopes”, stated European Southern Observatory engineer Markus Kasper. The improvement is not just visual, as it allows astronomers to resolve smaller details and detect objects that would remain hidden otherwise. One of the most important applications of this method is in the study of exoplanets. These planets are generally faint and located very close to much brighter stars, which makes it difficult to observe them. Adaptive optics systems that are supported by laser guide stars help in separating the light from planets and their host stars. Observations at facilities such as the Very Large Telescope in Chile use multiple lasers to improve coverage and detail, which makes it much easier to study planetary systems and surrounding dust structures (Nature, 2010).

The area that needs to be corrected can be expanded by using more than one artificial star. A study by Michael Hart and colleagues showed that multiple laser guide stars allow telescopes to model atmospheric turbulence in a more efficient manner. Their system improved the resolution by 30 to 50 percent across a wider field of view, which makes it possible to study dense star clusters and crowded galactic regions with more accuracy (Nature, 2010; PubMed). There are practical advantages beyond scientific capability. Space telescopes are expensive to build and difficult to upgrade once they are deployed. Ground-based systems using adaptive optics can be improved over time by updating lasers and software, which makes them more cost-effective. Upgrades can be carried out incrementally, which allows observatories to remain competitive without launching entirely new missions, according to ESO astronomer Paola Amico.

Technology is still evolving, more rapidly than ever before. The success of these technologies is based on the atmosphere and the ability to model the turbulence. There is also a limitation to the number of lasers that can be used and the area that can be corrected at one time. The study continues to improve the technologies, especially in the development of larger telescopes (AMOSTech; ADS Harvard). The laser guide star technologies represent a shift in the approach to the Earth's atmosphere, and scientists have begun to use them to their advantage rather than seeing the atmosphere. They have been able to improve the study of the atmosphere and opened the door to further study without having to rely on space-based telescopes by creating artificial reference points in the atmosphere.