Starshade: A starshade is a physical occulter placed between a star and a telescope that blocks out the light from the star, allowing the telescope to observe the planet. The starshade would need to be extremely precise and would require complex deployment and positioning in space.
Coronagraph: A coronagraph is an instrument that blocks out the light from a star by using a series of masks or focal plane optics. Coronagraphs can be used to directly image exoplanets, but they are limited by the amount of starlight they can block.
Phase-induced amplitude apodization (PIAA): PIAA is a technique that uses a series of diffractive optical elements to manipulate the light from a star in a way that cancels out the starlight and leaves the light from the planet visible.
Polarimetry: Polarimetry is a technique that measures the polarization of light. The light from a star is typically unpolarized, while the light from a planet can be polarized. By measuring the polarization of light, it is possible to separate the light from the planet from the light from the star.
Imaging spectroscopy: Imaging spectroscopy is a technique that measures the spectrum of light at each pixel in an image. By analyzing the spectrum of light, it is possible to determine the composition and temperature of a planet, as well as its distance from the star.
Some new concepts like exo-moons, which are moons orbiting an exoplanet, are extremely faint, and can be seen with a nulling interferometer. This instrument could be used to reduce the light of an exoplanet's star by 10 billion times, which would allow astronomers to directly detect extremely faint objects, such as exomoons.
These are just a few of the methods that have been proposed for suppressing starlight from a star in order to make its exoplanets more observable. As technology advances, it is possible that new and more effective methods will be developed.
