Orbital starshade paired with giant ground telescope could reveal rocky worlds
A NASA-led team has proposed a hybrid observatory that would combine an orbital starshade with the next-generation Extremely Large Telescope to block starlight and directly image Earth-sized exoplanets within about 20 light-years. The concept, called HOEE, would operate in optical light and could complement existing space-based instruments. The team has applied for further NASA funding to develop the idea.
The proposed starshade would measure roughly 50 meters across its central disk, with 48 petals extending 24.5 meters each, and would maintain positional accuracy within 6 meters using hydrogen-powered microthrusters. It would occupy an elliptical astro-stationary orbit about 175,000 kilometers from Earth, using chemical propulsion for station-keeping and solar electric propulsion to retarget between stars.
The concept targets planetary systems within 20 light-years, where reflected optical light from rocky worlds would be roughly one billion times fainter than their host stars. The team has submitted a Phase B proposal to NASA's Innovative Advanced Concepts program, with a decision expected by 2027, and the observatory would complement rather than replace existing space-based instruments like JWST and the Roman Space Telescope.
If realized, HOEE could substantially accelerate the search for habitable rocky worlds, potentially delivering the first direct optical images of Earth-sized exoplanets within a generation. This may reshape public understanding of humanity's place in the cosmos and influence future funding priorities in astronomy. Scientists and educators could gain unprecedented data on nearby planetary systems, while taxpayers may see value in a concept that leverages existing ground infrastructure rather than requiring a fully space-based observatory.