American Museum of Natural HistoryThe Lyot Project

How Do We Find Out More?

The principal barrier to comparative exoplanetary science today is the glare of the stars around which orbit the planets we seek to study. Two techniques have been identified that will enable direct detection and spectroscopy of exoplanets: optical interferometry and coronagraphy. Both techniques are being considered for NASA's Terrestrial Planet Finder a spacecraft whose purpose is to find and characterize planets similar to Earth. Because the Lyot Project is primarily concerned with extremely high-fidelity coronagraphy, we will not treat the interferometric techniques here. Information on interferometery can be found at NASA/JPL's Planetquest website.

The basic principle behind both approaches to eliminating the glare of the star is that one must start with an extremely good image of the star. The better the image of the star, the easier it is to understand using physics and optics theory. If the image is perfect, it can be deleted, leaving whatever else remains in the field of view.

Whenever an image is made using real optics, it is imperfect. However it is possible to correct many of the imperfections and drive the image to the point where it is very nearly perfect. This is what adaptive optics achieves. With a nearly perfect image, coronagraphy is one technique which can effectively remove most of the light from a star while having little effect on other objects in the field of view. The next two pages describe coronagraphy and adaptive optics.

Copyright © 2003 by Ben R. Oppenheimer