China joins the exoplanet hunt
China’s contributions to the detection and characterization of exoplanets have so far been limited. But the country — as with its expanding plans for Solar System exploration and planetary defense — has a keen interest in exoplanet studies and a growing research community focused on one of humanity’s key existential questions: are we alone?
The Xuntian space telescope is designed to conduct exoplanet research along with other sky survey tasks China is also working on its first dedicated exoplanet-hunting mission, named Earth 2.0, or ET, set to launch in 2028. That will be laser-focused on finding Earth-like planets around Sun-like stars using the transit method, while a microlensing camera, staring at the dense Galactic Bulge, will look for rogue planets as they pass in front of background stars. Another proposal, the Closeby Habitable Exoplanet Survey (CHES), could later be approved to seek out habitable planets.
Seeking biomarkers
Tianlin would be primed to follow up on the ongoing and future work of NASA’s TESS, the European Space Agency’s PLATO, and Earth 2.0. Together, these are expected to detect thousands of small to medium-sized planets using the transit technique, including habitable terrestrial planets around Sun-like stars. Tianlin would be able to follow up, searching spectra from exoplanetary transits across stars, to identify key molecules in atmospheres, such as water vapor, oxygen, and methane, that could indicate the presence of life. The authors of the Tianlin paper also state that simulations to test the potential for Tianlin to detect ozone and chlorophyll are planned.
Tianlin would also complement or even surpass other space-based telescopes. While JWST operates in the infrared, Tianlin could have a much broader range, allowing it to capture a wider array of astronomical data. It could also begin operations well before the Habitable Worlds Observatory, NASA’s next-generation, life-seeking telescope which could debut in the early 2040s.
In terms of getting off the ground and into space, Tianlin could launch on a Long March 5 — currently China’s largest rocket. Its maker is already working on an expanded payload fairing with a 6.4-meter (21-foot) diameter, meaning it may be able to encapsulate Tianlin. Another option would be the larger Long March 9 super heavy-lift rocket, currently in development.