Pandora: a small space telescope to complete James-Webb and find life in the Universe

Sometimes big discoveries are based on small innovations. This is perhaps what awaits us with NASA's future space telescope, Pandora, which should be launched in the fall of 2025. Its space bus has just been installed, a key step because it contains the instruments , processes data, manages space navigation and allows communication with Earth.

Pandora's mission will be to study the atmospheres of 39 exoplanets and the light of their 20 parent stars, with the aim of better studying how they can be habitable or not. The term “habitable” is not to be understood in the sense of “colonizable”, but only in the sense that life could develop there, independently of terrestrial life.

We have today identified 5819 exoplanets, of which approximately 10% to 20% are rocky (you can visit these exoplanets thanks to this NASA site). Those on which life more or less similar to terrestrial biology could develop would probably have liquid water on its surface, therefore an atmosphere to provide the appropriate pressure. The study of atmospheres is therefore crucial, but doesn't the James-Webb (JWST) do this better than anyone? Yes and no.

James Webb is too busy

“Although smaller and less sensitive than JWST, Pandora will be able to look longer at the host stars of extrasolar planets, allowing for more in-depth study.”said in a press briefing Dr. Daniel Apai of the University of Arizona, who leads the working group on the exoplanets selected for the mission.

“In 2018, a doctoral student in my group, Benjamin Rackham (now an MIT researcher), described an astrophysical effect whereby light coming directly from the star contaminates the signal of light passing through the exoplanet's atmosphereexplains Dr Apai. We predicted that this effect would limit the ability of James-Webb to study habitable planets.”

The wavelength at which this SmallSat (smaller, less expensive telescope) will observe will be near infrared and visible light. It will thus be better equipped to differentiate between starlight and the planetary atmosphere, whose emitted spectrum may be “polluted” by the star, for example by the presence of sunspots. Note that Pandora's infrared sensor is of excellent quality since it is a spare part initially intended for its big brother, the JWST.

Another point and not the least: the James-Webb is a star which is not limited to exoplanets. It tracks the galaxies of the deep Universe, the primordial stars and astronomers around the world wait months to get a few minutes of observation. More modest, Pandora will be able to study its targets with fewer restrictions.

Among the selected exoplanets, many orbit around M (red dwarfs, about 10% the size of the Sun) and K (orange dwarfs, about 80% the Sun) type stars, because these stars have planets orbiting quite close, which allows more frequent transits. They are also known to be eruptive with strong magnetic activity. This is precisely what needs to be studied: the impact of the star on the atmosphere and the habitability of exoplanets.

Pandora is therefore an inexpensive space mission compared to the gigantic James-Webb or the future Nancy-Grace-Roman Telescopethe cost of which is still estimated at around 4 billion dollars.