Planning is underway for NASA’s Habitable Worlds Observatory (HWO); This observatory will investigate the atmospheres of planets outside the Solar System to find signs of extraterrestrial life. This week, a workshop was held at the California Institute of Technology (Caltech) where scientists and engineers discussed the status of the technology that could be used in HWO, one of NASA’s next major telescope projects after the James Webb Space Telescope (JWST).

Looking for signs of life outside the solar system in the atmospheres of planets orbiting distant stars (exoplanets) is like looking for a needle in a cosmic haystack. After all, NASA estimates that there are several billion Earth-sized planets in the habitable zones of their stars, areas with the right temperatures for liquid water to exist. And that’s just in the Milky Way.

But scientists at least have a good idea of ​​what to look for and signs that could potentially point to life.

“We want to probe the atmospheres of these exoplanets for oxygen, methane, water vapor and other chemicals that might indicate the presence of life,” Nick Sigler, chief technologist for NASA’s exoplanet research program, said in a statement. said. “We’re not going to see little green men, but the spectral signatures of these important chemicals, or what we call biosignatures.”

HWO was first proposed as a top priority in the 2020 Decennial Review of Astronomy and Astrophysics (Astro2020), a roadmap of goals the astronomy community should achieve over the next decade. Because in addition to searching for signs of life outside the solar system and helping astronomers understand planetary systems, the observatory will also play an important role in astrophysical research.

Although the mission is planned to launch in the late 2030s or early 2040s, the advanced technologies the telescope will use now could help avoid cost overruns in the future, according to Dmitry Mavet, a member of HWO’s Technical Assessment Group (TAG).

HWO will use its ability to block the glow of the stars around which these exoplanets orbit to conduct deep studies of the atmospheres of exoplanets in search of signs of life.

Blocking the strong light from these stars will allow us to see the fainter patches of starlight reflected from the atmospheres of planets orbiting these stars. Chemical elements and compounds absorb and emit light at unique wavelengths characteristic of their composition; that is, light exposed to the planet’s atmosphere carries the signature of its constituent elements.

Scientists take this light and look for these fingerprints using a process called spectroscopy. Such chemical fingerprints may include biological signatures that indicate chemical compounds that living things inhale or inhale.

There are two main ways that HWO potentially blocks excess starlight. On the one hand, it can use a large external light unit called a starshade that, once launched, will transform from the HWO into a huge sunflower-shaped umbrella.

Or alternatively, it could use an internal stellar shield called a coronagraph, similar to the tools scientists use to study light from the Sun’s bright photosphere to study its hazy outer atmosphere, or corona. Sigler added that for now, NASA decided to focus HWO on coronagraph technology used on many other telescopes, including JWST and the upcoming Nancy Grace Telescope in Rome.

The WM Keck Observatory, located on Hawaii’s Mauna Kea, currently uses the Mawet-invented coronagraph together with the Keck Planet Imager and Characterizer (KPIC) to study exoplanets. The coronagraph allows KPIC to image thermal radiation from young, hot gas giant exoplanets, allowing scientists to study how these planets and planetary systems evolved.

The Earth-like planets that HWO will focus on may emit light about 10 billion times fainter than their stars; This means that the coronagraph for a future space telescope would have to emit starlight far beyond current limits.

“As we approach this required level of starlight suppression, the challenges become exponentially more difficult,” Mavet added.