An illustration of the potentially habitable exoplanet TOI 700 e. NASA.

Billions of Earth-Size Planets Exist in our Galaxy’s Habitable Zone: Here is How to Find Them

"We believe billions of Earth-size planets exist in our galaxy's habitable zone..."


Caltech’s brilliant minds have unveiled a groundbreaking space telescope concept, the Habitable Worlds Observatory (HWO). Poised to surpass NASA’s James Webb Space Telescope (JWST), HWO is designed to detect signs of life on Earth-like planets.

HWO’s mission isn’t just about finding life. It’s a comprehensive observatory set to explore stars, galaxies, and exoplanets. While the odds of spotting life on exoplanets might be slim, Caltech’s workshop focused on enhancing HWO’s technology to better these odds.


Dimitri Mawet, a distinguished member of HWO’s Technical Assessment Group and a seasoned researcher at the Jet Propulsion Laboratory (JPL), emphasized the need for innovation. “Our goal is to mature the necessary technologies, ensuring HWO delivers revolutionary science without risking unexpected expenses,” Mawet shared.

Mapping the Universe’s Future

Initially proposed as part of the Decadal Survey on Astronomy and Astrophysics 2020 (Astro2020), HWO is targeted for launch between the late 2030s and early 2040s. Its mission will oscillate between astrophysics and the study of exoplanets.

Caltech’s Fiona Harrison, a pivotal figure in the Astro2020 report, noted, “Astro2020 highlighted HWO due to its transformational potential in astrophysics and understanding other solar systems.”

A core feature of HWO is its ability to analyze exoplanet atmospheres for life indicators. To do this, it needs to efficiently block the blinding starlight. The proposed methods include an internal mask, or coronagraph, and an external, sunflower-shaped mask, called a starshade. Both these methods aim to illuminate the faint light reflected off a neighboring planet, much like blocking direct sunlight to capture a friend’s photo.


Once the planet’s light is captured, spectrometers will seek out chemical traces – potential indicators of life, or biosignatures.

“We believe billions of Earth-size planets exist in our galaxy’s habitable zone,” revealed Nick Siegler from NASA’s Exoplanet Exploration Program at JPL. “Our aim is to investigate these exoplanets’ atmospheres for vital chemicals that might hint at life.”

Sharpening the Lens

NASA is focusing on the coronagraph for HWO, leveraging lessons from the upcoming Nancy Grace Roman Space Telescope. Dimitri Mawet, known for his innovative vortex coronagraph at the Keck Planet Imager and Characterizer, emphasized the challenges. “Capturing images of Earth-twin planets demands advanced technology. Achieving the necessary starlight suppression becomes increasingly challenging,” he said.

To refine the coronagraph, the Caltech team discussed employing a precision-controlled deformable mirror. This technique minimizes stray light, ensuring clearer images of exoplanets.

The Nancy Grace Roman Space Telescope, slated for a 2027 launch, will pioneer this “active” coronagraph. Vanessa Bailey, a key figure at JPL, described the Roman Coronagraph Instrument as “NASA’s bridge to discovering extraterrestrial life.”

Mawet elaborated on the technical leaps required, “For HWO to succeed, we need to refine our mirror technology and enhance our starlight suppression capability.”

On the Horizon: Discovering Earth’s Twins

While the HWO’s launch is still years away, scientists have already begun their search. Over 5,500 exoplanets have been identified, but an Earth twin remains elusive. Yet, tools like the Caltech-led Keck Planet Finder continue to evolve, bringing the discovery of Earth twins closer to reality.


By HWO’s projected launch, scientists are optimistic about having a list of around 25 Earth-like candidates to scrutinize.

The path to these discoveries isn’t straightforward, but with collaboration, the sky’s the limit. As JPL director Laurie Leshin aptly summed up, “Facing such a challenge is exhilarating. We thrive on it, and we do it together.”

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Written by Ivan Petricevic

I've been writing passionately about ancient civilizations, history, alien life, and various other subjects for more than eight years. You may have seen me appear on Discovery Channel's What On Earth series, History Channel's Ancient Aliens, and Gaia's Ancient Civilizations among others.

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