Two Potentially Temperate Exoplanets Discovered in the Venus/Earth Zone

The low-mass stellar system LP 890-9 is comparable to our inner solar system, and the two planets detected could fit inside the orbit of Mercury. The outer planet (LP890-9c) may have insolation levels comparable to Earth’s and may potentially have liquid water. The inner planet (LP890-9b) has insolation levels close to that of Venus. Credit: Adeline Deward (RISE-Illustration).

In the age of exoplanet discovery, most planets found have either been large gaseous giants or large terrestrial planets orbiting very close to their stars. Both types of planets are poor candidates to host life as we understand it. In our solar system, Earth is the only known body on which life has evolved and been maintained. This is partly due to Earth’s orbital characteristics, typically the most important being heliocentric distance, that allow for liquid water and general temperate climates. Earth’s nearest neighbors currently do not allow for stable liquid water at their surfaces, Venus being too hot and Mars too cold. In extrasolar systems, the range of distances from the star in which an Earth-like body could have temperate climates and liquid water depends on the radiation received from that star. The search for potentially habitable planets focuses on this potentially temperate zone, the so-called habitable zone (HZ).

The planet-hunting Transiting Exoplanet Survey Satellite (TESS) mission discovered a potential planet in the HZ of a small star located around 100 light-years from Earth. Using ground-based telescopes sensitive to near-infrared radiation, an international team of researchers confirmed the detection of this planet and were surprised to discover a second planet. Both planets are so-called super-Earths, approximately 30-40% larger than Earth, with the inner planet outside the HZ (near Venus, if it were in our solar system) and the outer planet orbiting well within the HZ. However, residing in the HZ is not a guarantee of the existence of liquid water. Detailed observations and follow-up studies, particularly using the James Webb Space Telescope and advanced modeling of atmospheres, are needed to determine whether liquid water is at the surface. These exciting results point to the possibility of liquid water outside our solar system and may offer insight into the divergence of Earth and Venus close to home. READ MORE