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[Far and Wide Part 3: Exoplanets]
The same capabilities that make the James Webb and Nancy Grace Roman Space Telescopes such powerful tools for studying the early universe will also help them in another key mission: the search for and study of exoplanets, or worlds outside our solar system.
Roman’s ability to survey huge areas of sky with high precision gives Roman a unique ability in hunting for new exoplanets. Existing exoplanet missions like Kepler and TESS have been extremely successful at finding exoplanets through the transit method, where the planets block some of their host star’s light as they orbit past. But this method is limited in the systems it tends to find.
Roman should find thousands of planets through transits, but will mainly hunt for both smaller exoplanets and ones with larger orbits using a method called gravitational microlensing. When a planetary system passes between us and another star, the gravity of the nearer star and its planets bends and temporarily magnifies the background star’s light. This even works on so-called rogue planets, untethered to any star. Microlensing events are very rare, but Roman’s sky coverage will enable it to see many.
Roman also has a coronagraph technology demonstration instrument. Its primary goal is to test cutting-edge hardware for the first time in space. At its simplest, a coronagraph uses a disk to block the direct light of a star in order to better see what is around it. Roman’s dynamic coronagraph will use special masks, filters and deformable mirrors to actively sculpt the light rather than simply block it, giving finer control over reducing the star’s glare. This control should allow Roman to directly image – take actual pictures of – planets similar to Jupiter.
Webb is equipped with a static coronagraph, and along with its increased resolving power and sensitivity, Webb has a powerful suite of tools to study the light coming from exoplanets, whether radiating as heat from their surfaces, reflected starlight bouncing off them, or passing through their atmosphere as they orbit in front of their stars. By studying this light, scientists can see what wavelengths were emitted, reflected, or absorbed. Even if the planet itself isn’t visible as an object, its light can tell us a great deal about what it might look like if our equipment were sensitive enough. Because of this ability, Webb will be our prime tool for carefully studying the exoplanets we have found.
The continuing discovery and study of exoplanets, some with liquid water and some which are Earth-size, brings us closer to understanding the conditions necessary for life and where it might exist elsewhere in the galaxy. Roman will expand our catalogue of known worlds, and Webb will add detail to many entries within that catalogue. Together, they are poised to make some of the most important planetary discoveries of our lifetime.
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[NASA]