First, using the space telescope and “starshade,” or occulter, exoplanetary systems will be directly detected. Currently, Doppler techniques, which have been used to find over 200 extrasolar planets to date, have trouble detecting low-mass Earth-like planets. These techniques tell us little more than mass and orbit for the extrasolar planet. Using the newly developed technology regarding starshade design, we will be able to directly detect planetary systems surrounding stars other than our Sun.
Following detection, system mapping would involve the direct mapping of planetary systems through the detection of the planetary light separate from the parent star. In a sufficiently high-quality image, planets would appear as individual star-like objects. A series of images of the planetary system would allow us to measure the planetary orbits, and the brightness and broadband colors of the planets would give us information about the basic nature of each planet.
At this stage, detailed study of the individual planets will take place. With a low noise level and a modest signal, spectroscopy and photometry can be performed. Spectroscopy will allow us to perform chemical analysis of atmospheres and surfaces, which might hold clues to the existence of life elsewhere in the universe. Photometry will show variation in color and intensity as surface features rotate in and out of the field of view, allowing for the detection of oceans, continents, polar caps and clouds.
For more on spectroscopy, go here.
For more on photometry, go here.
A quantum leap in capability is needed to achieve true planet imaging. However, techniques of interferometry show that, in principle, this is possible to achieve. Fifty to one hundred percent of a planet’s surface could theoretically be mapped, depending on the planet’s inclination.
The final step in extrasolar planet studies will be the ability to study these distant worlds in the same way that Earth-observing systems study the Earth’s surface. Such a telescope will of necessity be large, to collect enough light to resolve and analyze small details on the planet’s surface. However, these kinds of studies do not lie in the foreseeable future, for it takes square kilometers of collecting area to capture the needed signal.