Two Earth-Like Exoplanets Detected Orbiting Nearby Star

Image Credit: Planetary Habitability Laboratory

The search for life elsewhere in the universe has just received another major boost. An international team led by the University of Göttingen has detected two planets orbiting the 24^th-nearest star to the Sun. Teegarden’s star is a red dwarf situated around 12.5 light years away from our solar system, and is approximately eight billion years old. More importantly, it is home to two Earth-like planets, Teegarden b and Teegarden c.

Both planets are believed to be terrestrial (rocky) worlds. Teegarden b has a mass of 1.05 Earth masses, orbits 0.0252 AU from its star, and takes a mere 4.91 days to complete a single orbit. Similarly, Teegarden c has a mass of 1.12 Earth masses, orbits 0.0443 AU from its star, and completes one orbit in 11.409 days. Both planets are among the 19 most habitable planets known to science out of a total of 4000 known planets. In fact, Teegarden b has the highest ESI (Earth Similarity Index) discovered so far.

Although it is possible that both planets could host liquid water on their surfaces, Teegarden b is the favoured candidate for habitability. There is a 60% chance that it has a temperate surface environment, indicating a range of temperatures from 0 to 50°C. This temperature could vary based on atmospheric composition, with 28°C being the likely surface temperature if the planet has an Earth-like atmosphere. Contrastingly, there is only a 3% chance that Teegarden c has a temperature surface environment, with the surface temperature likely being around -47°C if the planet has an Earth-like atmosphere.

Although these initial findings seem promising, especially for Teegarden b, further study is required to determine the extent to which these planets are habitable. These planets were discovered using the radial velocity method, and are unfortunately non-transiting. This means that in order to determine other key characteristics such as radius, direct observation with a future telescope such as the James Webb Space Telescope may be required. As well, red dwarfs are known to emit violent flares, which could be capable of destroying the planets’ atmospheres and sterilizing their surfaces. Due to how close the planets orbit their star, they may be tidally locked, meaning one side of the planet would face the star at all times. This could create two extreme sides to the planet, rather than an overall temperature climate, rendering the planets uninhabitable. Follow-up studies will be required in the future to further assess the habitability of these two worlds.

Read the original research paper here:

https://www.aanda.org/component/article?access=doi&doi=10.1051/0004-6361/201935460