HWO has two main methods of blocking excess starlight. On the one hand, it can use an external light barrier called a star canopy, which will open in the form of an umbrella after launch. The second method is to use a star shade called a coronagraph. This canopy is similar to a tool scientists use to block the sun’s bright photosphere and study its outer atmosphere, or solar corona. NASA plans to use coronagraphy technology for HWO, which has been used in other telescopes such as the James Webb and Nancy Grace Roman telescopes.
Observatory of W. M. Located on Mauna Kea in Hawaii, Keck uses the Coronagraph in conjunction with the Keck Planetary Imager (KPIC) to study exoplanets. The coronagraph allows KPIC to image the heat rays of young, hot gas giant exoplanets. In this way, scientists can understand how planets and their systems evolve.
The Earth-like planets targeted by the HWO can also emit as much as 10 billion times less light than their stars. As a result, the coronagraph of this telescope must block the starlight as much as possible. As we approach the level required to compress starlight, more difficult challenges will arise.
Blocking starlight with a deforming mirror
One of Caltech’s ideas to improve the blocking of light from a distant star is to put a mirror inside the coronagraph that can change the shape of the light rays. Using thousands of actuators to control the shape of the mirror as well as the traction and thrust of reflective surfaces can prevent disturbing light from entering the final image and creating unwanted spots. This type of deformable mirror is also used in the Nancy Grace Roman telescope. This space observatory will probably not be launched before 2027. The Roman telescope allows astronomers to see gas giants hundreds of millions of times fainter than stars, as well as debris left over from the birth of planets.
The above efforts are important building blocks towards more powerful technology embedded in HWO. According to Maut, the mirrors must be modified at the level of picometric accuracy. During a meeting held at Caltech, scientists determined the best type of mirror needed for the HWO and its coating, as well as other possible instruments for the telescope.
As planning for HWO continues, astronomers are also working to select Earth-like exoplanet targets. The effort involves using the Keck Planet Finder (KPF) at the Keck Observatory, which is designed to target Earth-like planets in the habitable belt of red dwarf stars.