The Habitable Worlds Observatory (HWO) is a proposed next generation space telescope, a successor of the flagship Hubble, Webb and Roman projects. It would have a large 6–8 meter mirror and be able to detect infrared, optical, and ultraviolet wavelengths. Its primary mission would be to search for and image Earth-size habitable exoplanets in the habitable zones of their stars, where liquid water can exist, by using a coronagraph or a starshade to block out the light of their stars. Beyond planets, it will also observe galaxies.^[1] The proposed launch date is 2041, a tentative date because U.S. President Donald Trump has promised to defund and dismantle the Roman telescope only a year away from launch.^[2]

HWO’s main objective would be to identify and directly image at least 25 potentially habitable worlds. It would then use spectroscopy to search for chemical biosignatures in these planets’ atmospheres, including gases such as oxygen and methane, which could serve as critical evidence for life. HWO would also use its high sensitivity and resolution capabilities to trace the evolution of galaxies and other cosmic structures.^[3]

The main science themes for HWO are:^[1]

• Living worlds - search for life
• Drivers of galaxy growth - show how galaxies change over the lifetime of the universe
• Evolution of elements over cosmic time - study how elements arise in stars and are redistributed
• Solar System in its galactic context - study objects in the Solar System

The concept for HWO came out of two earlier ideas called the Large Ultraviolet Optical Infrared Surveyor and Habitable Exoplanets Observatory. HWO was officially recommended in 2020 by the National Academies’ Decadal Survey on Astronomy and Astrophysics.^[4] In 2023, the National Aeronautics and Space Administration (NASA) established a Great Observatory Maturation Program (GOMAP) to unite government, industry, and academia to develop the technologies needed for HWO.^[3] GOMAP aims to draw on lessons from previous NASA missions to streamline development of the HWO concept and decrease budget and schedule risks for the future mission.

The HWO is designed to be launched on a super heavy-lift launch vehicle such as SpaceX's Starship, Blue Origin's New Glenn or the SLS.^[5] The design for the HWO includes a 6–8 meter mirror, however it would allow for a larger mirror if launch vehicle technology allows by the time of its launch in the 2040s.^[5]