China plans to build an exoplanet observatory in 2028 in a bid to make a breakthrough in detecting a potential second Earth. About 5,000 exoplanets have been discovered since 1995, but no Earth-sized planets have been detected in the habitable zones of sun-like stars.

Proposed by the Shanghai Astronomical Observatory of the Chinese Academy of Sciences (CAS), Earth 2.0, or ET, aims to use six 28-centimeter wide-field optical telescopes to observe about 2 million stars in the Kepler mission’s star field, while also observing larger nearby transits, called exoplanets, continuously for four years.

According to a new paper written by the mission’s principal investigator and others and published in the Chinese Journal of Space Science, the mission aims to launch in 2028. The spacecraft will be launched to the Sun-Earth Lagrange Point 2, the same gravitationally stable region of space as the James Webb Space Telescope, which will provide a stable orbit, a stable view of deep space and reduced interference from Earth.

There, ET’s optimized transit telescopes will provide high photometric precision (the precision and consistency with which the telescopes can measure the brightness of stars), allowing the detection of small rocky planets that have eluded previous missions such as NASA’s Kepler exoplanet probe and observatory.

While Earth-like planets have been discovered, they have been found in relatively short orbits around sufficiently bright stars or small, massive red dwarfs that emit strong radiation. ET will be able to look at target areas of the sky for extended periods. This extended observation time will allow the detection of planets with longer orbital periods in the habitable zones around Sun-like stars, potentially allowing signals from exo-Earths to be received.

The world’s fundamental questions and journeys

The mission will focus on three key questions: the prevalence of exo-Earths in the galaxy, the formation and evolution of terrestrial planets, and the origin of free-floating planets. The mission is well-positioned to make a significant contribution to exo-Earth research, according to Jesse Christiansen, principal scientist of NASA’s Exoplanet Science Institute at Caltech/IPAC.

“Given our increasing knowledge of the frequency of formation of Earth-like planets, the ET team was able to develop a more probable probe than Kepler or PLATO. [Європейського космічного агентства]will reveal these planets.

“This will primarily be for a much larger sample of stars; the mission will obtain the high-precision photometry needed to detect Earth, with a wider field of view than Kepler and with high precision down to a lower magnitude,” Christiansen said. Space News.

The rogue planet problem will be investigated using a 35-centimeter microlens telescope. This instrument will observe about 30 million stars in the Galactic Bulge to detect microlensing events caused by free-floating or “rogue” planets. These events occur when planets create a gravitational lensing effect on the light of background stars, detected by observing characteristic anomalies in the star’s brightness curve. The hope is to find a “wandering Earth” in deep space, free of stars.

Technological progress, its impact on research

According to the newspaper, ET development is progressing well. It describes advanced technologies important to the mission, including photometric accuracy, satellite stability and a CMOS detector for thermal control. All are almost ready to fly.

Once Sun-Earth L2 is reached and fully operational, ET can begin advanced work on finding exo-worlds, otherwise this may not happen for some time.

“Currently, the only mission scheduled to fly in the next decade that will be able to detect Earth-like planets is NASA’s Nancy Grace Space Telescope in Rome, which will detect them only through microlensing, a fleeting measurement of a distant signal that quickly reappears. These planets will be useful for statistical understanding of the habitable properties of the galaxy, but they will not represent valuable individual planets that we want to characterize in detail with other telescopes.”

The Rome Space Telescope is expected to launch in 2027.

“Additionally, NASA’s next flagship mission, the Habitable Worlds Observatory (HWO), is more than 20 years away. If ET receives funding and flies within the next decade, it could discover nearby habitable planets decades earlier than planned.”

The mission will not only look for promising extraterrestrial candidates, but will also allow for follow-up observations to further characterize such candidates. ET will work with China’s ground-based optical telescope LAMOST to provide spectral observations from the observatory, as well as with other groups and observatories on Earth and in space.

According to the paper, this would lead to precise measurements of the mass, density and atmospheric composition of any exo-Earth candidate, paving the way for in-depth studies of their habitability properties.

“Game Changer”

Wang Chi, director of the National Space Science Center (NSSC) led by CAS, said in April that the ET mission was selected from among astronomy and space exploration missions. Lunar astronomy, extreme space physics, solar observatory and gravitational wave missions were also approved. Each of the selected missions aims to expand the frontiers of knowledge. According to Christiansen, ET could be a game changer.

“We’ve been searching for Earth 2.0 for a long time, and we’ve hit every crossroads so far,” says Christiansen. “If ET can finally and reliably find a rocky planet in the habitable zone of a Sun-like star, it would be an incredible achievement.

“If it’s a planet that we can study with JWST or other telescopes like HWO in the future, that’s a game changer.”

Table representing the main goals of the Earth 2.0/ET mission.