Earth 2.0? China joins the race to find the most Earth-like habitable exoplanet

NASA recently announced that it has discovered more than 5,000 exoplanets, mainly thanks to the Kepler telescope, which ceased operations in 2018. However, none of these technically fit the definition of Earth 2.0 as they don't orbit the habitable zone of a Sun sufficiently like our own.

China's space agency hopes to be the first to make that discovery. Its new project, which will be funded by the Chinese Academy of Sciences, is currently in the early design phase, with an assessment by an expert panel slated for June. If all goes to plan, that panel will give the team the green light to start building their satellite. The space observatory is expected to launch aboard a Long March rocket by 2026.

"Our satellite can be 10–15 times more powerful than NASA's Kepler telescope in its sky-surveying capacity," says Jian Ge, the astronomer leading the Earth 2.0 mission at the Shanghai Astronomical Observatory of the Chinese Academy of Sciences.

China's Earth 2.0 satellite is designed to carry seven telescopes, six of which will survey the Cygnus–Lyra constellations that were observed by NASA's Kepler telescope. It will have the capacity to observe approximately 1.2 million stars across a 500-square-degree patch of sky, which is almost 5 times wider than Kepler's view. It will also be able to observe dimmer and more distant stars than NASA's operational Transiting Exoplanet Survey Satellite (TESS), which observes stars nearer Earth.

"There will be a lot of data"

The Earth 2.0 satellite's six main telescopes will find exoplanets by detecting dips in the brightness of stars — demonstrating that a planet is orbiting. The Earth 2.0 satellite's seventh instrument will be a gravitational microlensing telescope, and it will be used primarily to search for rogue planets that don't orbit any star, as well as exoplanets that orbit far away from their star.

"Our satellite can essentially conduct a census that identifies exoplanets of different sizes, masses, and ages. The mission will provide a good collection of exoplanet samples for future research," Ge says.

In order to find an Earth 2.0, scientists will need to observe that it has a similar orbit to Earth, transiting its Sun roughly once a year, meaning it could take several years to collect the required data. That's why China's Earth 2.0 satellite will be trained on a particularly populated section of the Milky Way for four years. "There will be a lot of data, so we need all the hands we can get," Ge says. "Earth 2.0 is an opportunity for better international collaboration."

The European Space Agency (ESA) is also working on its own Earth 2.0 project, called Planetary Transits and Oscillations of Stars (PLATO). It will carry 26 telescopes and will change its area of observation every two years. NASA, meanwhile will soon also train its James Webb telescope on alien worlds. Whoever wins the race, the liklihood of finding Earth 2.0 increases massively with every mission that launches.