NASA is developing technology to shield starlight to search for signs of life in the atmospheres of planets. Recently, a workshop was held at the California Institute of Technology (Caltech) to discuss the technology that could be used by the Habitable Worlds Observatory (HWO), one of NASA’s next major space telescopes following the James Webb Space Telescope (JWST). The Habitable Worlds Observatory is where scientists will scan the atmospheres of planets outside our solar system to search for signs of life.
Searching for signs of life on planets outside the solar system is akin to searching for a needle in a haystack. However, scientists at least have ideas about what to look for and specific knowledge about the signs that could indicate life.
Nick Siegler, the technology director for NASA’s Exoplanet Exploration Program, stated in a release, “We want to probe the atmospheres of these exoplanets to look for oxygen, methane, water vapor, and other chemicals that can be signs of life. We won’t find tiny green men, but we might find the spectral fingerprints of important chemicals, also known as biosignatures.”
To conduct in-depth studies of the atmospheres of exoplanets, HWO will utilize the ability to block out the bright light from the star the exoplanets orbit. Blocking this glare allows scientists to observe the fainter starlight reflected off the atmospheres of exoplanets. The elements and chemical compounds absorb and emit light at characteristic wavelengths, meaning that the light interacting with a planet’s atmosphere carries traces of the elements that compose it.
Scientists capture this light and use a process called spectroscopy to search for “biological fingerprints,” including signs of chemical compounds that living organisms either exhale or inhale.
Planets similar to Earth that HWO targets can emit light fainter by about 10 billion times compared to the light from their stars. There are two main ways for HWO to block out the starlight. The first method involves using a large external light-blocking device known as a starshade, which unfurls after being launched from HWO into a giant sunflower-shaped disk. Alternatively, the second method involves using an internal starshade known as a coronagraph, similar to the tool scientists use to block out light from the sun’s photosphere to study the outer solar atmosphere, or corona.
One idea discussed at the Caltech workshop to enhance the ability to block starlight is to place a deformable mirror inside a coronagraph to control the light beams. Dmitry Mawet, a member of the HWO Technical Assessment Group (TAG), said, “We need to deform the mirrors to the picometer level.” He added, “The workshop helped us pinpoint the gaps in the technology and where we need to develop further in the coming decade.”