French-American cooperation produces polychromatic guide star

French-American cooperation produces polychromatic guide star

While continuing experiments at Lawrence Livermore National Laboratory (LLNL, Livermore, CA) to refine laser guide stars for astronomy, visiting French researchers last month conducted tests using a 400-W polychromatic laser beam. Projection of a single beam containing 589 and 569 nm produced the first amber-colored guide star. Previous LLNL experiments were limited to just a 589-nm beam from a copper-vapor-pumped dye laser. The French researchers believe multicolor guide stars can give information on the average tilt of stellar wavefronts, which cannot be inferred by single-color guide stars. Sharper images provided by polychromatic guide stars might benefit the search for planets around nearby stars, where faint planets would normally be lost in the scattered light from a bright star, and high-resolution studies of matter falling into giant black holes in the center of galaxies.