Most of the 5000 exoplanets discovered so far have been found using methods that don’t actually see the planet at all. Brightness dimmings and star wobbles only get us so far. They limit our ability to study them in detail and astronomers are working on gigantic starshades to resolve planets directly.
Direct imaging is a technique that can be used to take pictures of exoplanets. But this is a much more challenging task than indirect methods, because the light from the exoplanet is much fainter than the light from the star it orbits. However, direct imaging is the only way to obtain detailed information about the physical properties of exoplanets, such as their geography, shape, and atmosphere.
One way to improve the sensitivity of direct imaging is to use a starshade. A starshade is a large, deployable structure that looks a lot like a gigantic flower that blocks out the light from a star, allowing a telescope to see the fainter light from an orbiting planet. Starshades are still in the development stage, but they have the potential to revolutionize the field of exoplanet research.
How does a starshade work? It works by creating a shadow in the space between the telescope and the star. The shadow is created by the starshade’s petals, which are arranged in a circular or hexagonal pattern. The shape of the petals is designed to reduce diffraction and minimize the amount of stray light that enters the shadow.
The starshade is positioned in front of the telescope, and the telescope is pointed at the star. With the light from the star blocked, the reflected light from the planet is revealed and the telescope can then see the faint glow.
There are several challenges associated with using starshades to find exoplanets. One challenge is the size of the starshade. They are huge and they need to be large enough to block out the light from the star, but they also need to be light enough to be deployed in space.
Another challenge is the alignment of the starshade. It needs to be aligned very precisely with the telescope in order to create a sharp shadow.
There are several ongoing projects to develop starshades. One project is the HabEx mission, which is a joint project between NASA and the European Space Agency. The HabEx mission would use a starshade to search for Earth-like planets around nearby stars.
Another project is the Roman Starshade Rendezvous, which is a NASA mission that will attempt to directly image the habitable zones of nearby sun-like stars. They will attempt to determine whether Earth-like exoplanets exist in the HZs of the nearest sunlike stars and have biosignature gases in their atmospheres.
The development of starshades is still in the early stages, but they have the potential to make major advances in our understanding of exoplanets. Starshades could help us to find new exoplanets, to study their atmospheres, and to search for signs of life.