American Scientist

More than 5,000 exoplanets—planets that are outside our Solar System—have been identified so far. But we haven’t actually seen any. So how have they been identified? Most often, detection techniques involve a disruption in another signal, such as a dip in the light from a star when its orbiting planet crosses in front of it, from the viewpoint of Earth. This phenomenon, called transiting, has been covered many times in American Scientist’s pages. The difficulty with exoplanet detection remains that most of the methods currently used have drawbacks, such as a lengthy time delay between measurements, making it more likely that errors in measurement will creep in. Optical scientist Marija Strojnik describes another potential detection method that uses the wave nature of light, which could allow for more accuracy. In “Direct Detection of Exoplanets,” Strojnik shows that curved light wave fronts coming from distant exoplanet systems become planar over long distances, and those wave fronts create a detectable signal. The wave front from an exoplanet will develop a tilt in relation to the wave front from its star, because of the planet’s off-axis position. Those two wave fronts can be combined by a detector, essentially creating an interference pattern that would not exist if the exoplanet wasn’t there.