In early August, scientists and engineers gathered in a small auditorium at Caltech to discuss how to build the first space telescope capable of detecting life on planets like Earth. The proposed mission concept, called the Habitable Worlds Observatory (HWO), would be the next powerful astrophysics observatory after NASA's James Webb Space Telescope (JWST). It would have the ability to study stars, galaxies, and a host of other cosmic objects, including planets outside our solar system, which are known as exoplanets. Though finding life on exoplanets maybe be a long shot, the Caltech workshop aimed to assess the state of technology needed by HWO to search for life elsewhere.
"Before we can design the mission, we need to develop the key technologies as much as possible," says Dimitri Mawet, a member of the Technical Assessment Group (TAG) for HWO, the David Morrisroe Professor of Astronomy, and a senior research scientist at the Jet Propulsion Laboratory (JPL), which is managed by Caltech for NASA. "We are in a phase of technology maturation. The idea is to further advance the technologies that will enable the Habitable Worlds Observatory to deliver its revolutionary science while minimizing the risks of cost overruns down the line."
First proposed as part the National Academy of Sciences' Decadal Survey on Astronomy and Astrophysics 2020 (Astro2020), a 10-year roadmap that outlines goals for the astronomy community, HWO would launch in the late 2030s or early 2040s. The mission's observing time would be divided between general astrophysics and exoplanet studies.
"The Decadal Survey recommended this mission as its top priority because of the transformational capabilities it would have for astrophysics, together with its ability to understand entire solar systems outside of our own," says Fiona Harrison, one of two chairs of the Astro2020 decadal report and the Harold A. Rosen Professor of Physics at Caltech, as well as the Kent and Joyce Kresa Leadership Chair of the Division of Physics, Mathematics and Astronomy.
The space telescope's ability to characterize the atmospheres of exoplanets, and therefore look for signatures that could indicate life, depends on technologies that block the glare from a distant star. There are two main ways of blocking the star's light: a small mask internal to the telescope, known as a coronagraph, and a large mask external to the telescope, known as a starshade. In space, starshades would unfurl into a giant sunflower-shaped structure, as seen in this animation.
In both cases, the light of stars is blocked so that faint starlight reflecting off a nearby planet is revealed. The process is similar to holding your hand up to block the sun while snapping a picture of your smiling friends. By directly capturing the light of a planet, researchers can then use other instruments called spectrometers to scrutinize that light in search of the chemical signatures. If any life is present on a planet orbiting a distant star, then the collective inhales and exhales of that life might be detectable in the form of biosignatures.
