In Search of Extraterrestrial Life: Advances in Coronagraphy, Starshade Technology, and the Detection of Alien Biosignatures

The illustration outlines the configuration of a space telescope in alignment with a starshade, a technology employed to obstruct starlight for the purpose of revealing planets in orbit around that star.
Credit: NASA/JPL-Caltech

Preparations for NASA’s Habitable Planetary Observatory Underway

In the early days of August, a confluence of researchers and engineers convened in a compact auditorium at the California Institute of Technology (Caltech) to deliberate on the construction of the inaugural space telescope capable of identifying life on Earth-like planets. This envisioned mission, referred to as the Habitable Planetary Observatory (HPO), is slated to be the successor to NASA’s James Webb Space Telescope in the domain of advanced astrophysical research. The telescope would be engineered to scrutinize a plethora of celestial bodies, including exoplanets, which are planets situated outside our solar system. Although the possibility of discovering life on these foreign worlds is speculative, the Caltech forum aimed to evaluate the requisite technological state for the HPO mission.

“To advance the mission design, preliminary technologies must be matured,” notes Dimitri Mawet, part of the Technical Assessment Group for HPO, David Morrisroe Professor of Astronomy, and a lead research scientist at the Jet Propulsion Laboratory (JPL) managed by Caltech for NASA. “The current phase is one of technology maturation with the objective of advancing the technologies that would allow the Habitable Planetary Observatory to accomplish its groundbreaking scientific aims while mitigating financial risks.”

Overview and Objective of HPO

Initially suggested as part of the Decadal Survey on Astronomy and Astrophysics 2020 (Astro2020), a ten-year strategic framework for the astronomical community, HPO is planned for a launch either in the late 2030s or early 2040s. The mission’s observation period would be split between general astrophysics and the study of exoplanets.

“Fiona Harrison, one of the co-chairs of the Astro2020 Decadal Survey, asserts that this mission is prioritized highly due to its revolutionary capabilities in astrophysics, coupled with its potential to explore entire solar systems beyond our own,” says Harrison, who is also the Harold A. Rosen Professor of Physics at Caltech.

Technological Innovations and Impediments

The effectiveness of the space telescope in analyzing the atmospheres of exoplanets, and thereby searching for life indicators, hinges on mechanisms that can shield the blinding light from distant stars. Two primary techniques for this purpose exist: an internal mask within the telescope, known as a coronagraph, and an external mask known as a starshade. Starshades in space would expand into a large, sunflower-like formation.

In either technique, the objective is to obstruct starlight to unveil the faint light reflected off nearby planets. Capturing this light allows scientists to subsequently use spectrometers to analyze it for chemical traces. If life exists on a distant planet, its biosignatures might be detectable through this process.

“We approximate the existence of several billion Earth-sized planets in our galaxy’s habitable zone,” says Nick Siegler, the head technologist for NASA’s Exoplanet Exploration Program. “Our aim is to examine the atmospheres of these planets for indicators like oxygen, methane, and water vapor, which could signify life.”

Future Prospects and Challenges

Advancements in coronagraphic technologies are already occurring. Mawet has developed vortex coronagraphs, situated in the Keck Planet Imager and Characterizer, that can capture images of exoplanets a million times dimmer than their host stars. Yet, imaging Earth-like planets—where life is most plausible—will necessitate substantial advancements in current technologies.

“As the necessary level of starlight suppression becomes increasingly stringent, the technological challenges escalate exponentially,” states Mawet.

Scientists at the Caltech seminar discussed the latest coronagraphic methods, which include the manipulation of light waves with ultra-precise deformable mirrors. The future Roman Coronagraph Instrument will be the pioneer in using this active mirror technology.

Vanessa Bailey, the technologist for the Roman Coronagraph, indicates, “This instrument serves as an intermediate step towards achieving the objectives of the Habitable Planetary Observatory. It will test several new technologies at unprecedented levels of performance.”

By the time HPO is projected to launch, the scientific community anticipates having a list of at least 25 Earth-like candidates for detailed exploration. Although the journey ahead is arduous, the scientists express enthusiasm for the challenges, affirming that such groundbreaking endeavors are a collaborative effort.

Frequently Asked Questions (FAQs) about Habitable Worlds Observatory

More about Habitable Worlds Observatory

• NASA’s Official Page on the Habitable Worlds Observatory
• Technical Assessment Group (TAG) for HWO
• Decadal Survey on Astronomy and Astrophysics 2020
• Nancy Grace Roman Space Telescope
• Jet Propulsion Laboratory (JPL) Managed by Caltech
• What are Coronagraphs and Starshades?
• Spectrometers in Astronomy
• Significance of Biosignatures
• Challenges in Direct Imaging of Exoplanets