tics more practical. Before correcting the blurring of an observed object, AO systems must measure the atmospheric distortion. Sometimes a nearby bright star can be used as a "guide star," to measure this distortion. More often, no bright star is near enough to the object to be observed. The Lick LGS system actually creates a guide "star" by shooting a laser beam into the sky, making sodium ions in the upper atmospere glow. The atmospheric distortion is measured using this manmade "star," and the deformable mirror is adjusted accordingly to get a clear view of the observed object. This system is now being used at observatories throughout the world.
Please see the Adaptive Optics webpage for more details about AO engineering and observation at Lick Observatory.
Light pollution, or light from communities and industries adjacent to observatories that reduces the accuracy of observation, is an increasing problem throughout the world today. Astronomers are increasingly interested in infrared (IR) observation, which measures wavelengths that we perceive as heat, because there is less earth-based "pollution" in this area of the spectrum. Many new IR cameras and spectrographs are being designed and built.
Mt. Hamilton is less light-polluted than many observatories, thanks to the city of San Jose. San Jose employs low-pressure sodium vapor streetlights which "pollute" only one small area of the spectrum. However, the night sky over Mt. Hamilton is even more "dark" (without interference) in the IR range.
Many astronomical processes create IR radiation that can be observed and analyzed. Examples include star formation, forming and colliding galaxies, novae and supernovae, and the event horizons of black holes. Astronomers can quantify IR radiation from around "room temperature" to several thousand degrees above absolute zero.
IR radiation also penetrates cosmic dust clouds more easily than visible light. This makes IR observation superior to visible light observation if the process itself is dusty, such as star formation The image to the left reveals a dense cluster of young stars (reddish region in center) which is obscured at visible wavelengths by the nebula's dark central dust lane. (NGC 2024 image courtesy Ian McLean and UCLA IR Lab.) IR observation is also practical for observing remote objects when there are cosmic dust clouds between the object observed and the observer.
The now-retired Lick Infrared Camera (LIRC-II) was an early pioneeer in IR imaging, used at the Cassegrain foci of both the Shane and Nickel telescopes. The Gemini IR Imaging Camera, built at UCLA Infrared Labs, is currently used with the Shane telescope. IR-sensitive instruments are being built for Adaptive Optics (AO), and IR-sensitive CCDs are being developed. Clearly, IR observation and imaging will be widely used in future research at Lick Observatory, and throughout the world.