China Focus: China plans to launch large space telescope for exoplanets around 2035

BEIJING, May 20 (Xinhua) -- China is funding the concept study and considering funding the feasibility study of a large space telescope that looks for exoplanets and aims to start operation around 2035, according to its researchers.

Named Tianlin or "neighbor in the sky" in Chinese, the 6-meter class UV to optical space telescope will be mainly dedicated to looking for Earth-like planets, particularly Earth twins in the habitable zones around nearby stars, according to researchers from the Key Laboratory of Optical Astronomy under National Astronomical Observatories in Beijing.

The habitable zone is the not-too-hot and not-too-cold regions around a star where liquid water can exist on a planet's surface.

The Tianlin telescope, with an aperture size of 6 meters, will be launched to the Sun-Earth L2 point halo orbit. The L2 point of the Earth-Sun system is ideal for astronomy because a spacecraft is close enough to communicate with the Earth, can keep the sun, Earth and moon behind the spacecraft for solar power, and offers a clear view of deep space for telescopes.

The telescope will use four Fine Guiding Sensors, the Wide Range High Dispersion Spectrograph, the High Spatial Resolution Camera, and the High Contrast Coronagraph, to capture spectral features from ozone, oxygen, water and methane.

The mission's primary goal is to search and characterize the atmospheres of nearby exoplanets, particularly Earth-like planets and close-in rocky planets around G and K stars, to explore their habitability, and to search for potential biosignatures in their atmospheres or on their surfaces, said the researchers.

Stars like our Sun are classified as G stars. They are yellow with surface temperatures of 5000 to 6000 K (4726.85 degrees Celsius to 5726.86 degrees Celsius). K Stars are less massive and cooler than our Sun, and they are yellow to orange at about 3500 to 5000 K.

The secondary science goal is to obtain a comprehensive understanding of various types of planets and planetary systems in terms of what they are made of, how they form and evolve, and what shapes their atmospheres by conducting an in-depth spectroscopic survey of a sample (more than 100) of nearby rocky and gas planets with precision and accuracy.

The entire observatory, including the telescope and instruments, will weigh about 15.6 tonnes. It will be stationed on a spacecraft platform that is to be developed in conjunction with the telescope, to realize high dynamical and thermal stability required by the mission goals.

According to the researchers, the overall payload may weigh 40 tonnes, and is to be launched around 2035 by the next-generation Chinese heavy carrier rocket Long March-9.

The China Aerospace Science and Technology Corporation, developer of the Long March carrier rocket series, said in 2019 that the Long March-9 is expected to make its maiden flight around 2030 and will support manned lunar exploration, deep space exploration and construction of a space-based solar power plant.

When Tianlin is in position in the 2030s, it will be the first-of-its-kind facility in the world to learn about extra-solar lives, said the researchers. The telescope is designed to have a nominal operational mission lifetime of at least 10 years.

The mission will either return the first detection of extra-solar biosignatures or otherwise imply to us that our Earth is the only planet with life developed in the nearby universe within telescope detection limitations.