A few months ago, a group of NASA exoplanet astronomers, who are in the business of discovering planets around other stars, called me into a secret meeting to tell me about a planet that had captured their interest. Because my expertise lies in modeling the climate of exoplanets, they asked me to figure out whether this new planet was habitable — a place where liquid water might exist.
These NASA colleagues, Josh Schlieder and his students Emily Gilbert, Tom Barclay and Elisa Quintana, had been studying data from TESS (Transiting Exoplanet Survey Satellite) when they discovered what may be TESS’ first known Earth-sized planet in a zone where liquid water could exist on the surface of a terrestrial planet. This is very exciting news because this new planet is relatively close to Earth, and it may be possible to observe its atmosphere with either the James Webb Space Telescope or ground-based large telescopes.
Habitable zone planets
The host star of the planet that Gilbert’s team discovered is called TESS of Interest number 700, or TOI-700. Compared to the Sun, it is a small, dim star. It is 40% the size, only about 1/50 of the Sun’s brightness and is located about 100 light-years from Earth in the constellation Dorado, which is visible from our Southern Hemisphere. For comparison, the nearest star to us, Proxima Centauri, is 4.2 light-years away from Earth. To get a sense of these distances, if you were to travel on the fastest spacecraft (Parker Solar Probe) to reach Proxima Centauri, it would take nearly 20,000 years.