An article published in the journal “Astronomy & Astrophysics” reports the identification of the exoplanet Wolf 1069 b, which has a mass close to the Earth’s and orbits within its star system’s habitable zone. A team of researchers led by Diana Kossakowski of the Max Planck Institute for Astronomy used the CARMENES spectrographs mounted on the 3.5-metre telescope of the Calar Alto Observatory, Spain, to identify traces of Wolf 1069 b using the radial velocity method. This exoplanet is tidally locked with its star, which poses a problem for habitability, but its star doesn’t have powerful flares. These characteristics make Wolf 1069 b an interesting object of study.
The star Wolf 1069 is a red dwarf with a mass that is only about one-sixth of the Sun’s. For this reason, the energy it emits is far lower than the Sun’s and its system’s habitable zone is much closer to it compared to that of the solar system. The exoplanet Wolf 1069 b has a year that lasts just over 15 Earth days but it’s within that zone.
The image (© MPIA graphics department/J. Neidel) illustrates a comparison between the systems of Wolf 1069, Proxima Centauri, and TRAPPIST-1. These are three systems with red dwarf stars and rocky planets, including some in the habitable zone.
The CARMENES (Calar Alto high-Resolution search for M dwarfs with Exoearths with Near-infrared and optical Echelle Spectrographs) instrument aims to study red dwarfs in search of Earth-like planets using a pair of spectrographs. In the case of the Wolf 1069 system, the observations produced data that, analyzed using the radial velocity method, indicated the presence of a planet with interesting characteristics.
The exoplanet Wolf 1069 b wasn’t directly observed, so it was possible to obtain only limited data about it. The estimate of its mass indicates a minimum value that is about 1.26 times the Earth’s. Follow-up studies are needed, also with other instruments, to obtain more precise estimates but the initial data is interesting.
One problem is that we don’t know if Wolf 1069 b has an atmosphere. Red dwarfs are small but often very active stars with powerful flares and even a planet protected by a magnetic field risks ending up like Mars. The star Wolf 1069 looks quiet and in those conditions, a rocky planet can maintain an atmosphere.
A planet close to its star such as Wolf 1069 b is tidally locked with it, which means that it always shows the same face to it. If it had an atmosphere similar to the Earth’s, the average temperature on its surface would be 250 Kelvin, -23° Celsius. The water would be frozen over much of the surface but on the day side, it could reach 286 Kelvin, 13° Celsius. These are not easy conditions but water would be liquid over a large area of the day side.
At just over 31 light-years from Earth, the Wolf 1069 system is interesting and can be the subject of follow-up studies even though it might be impossible to directly see the exoplanet Wolf 1069 b. New studies could also look for other planets in that system: the analysis of data collected with the CARMENES instrument indicates that there is no planet closer to its star than the one just presented but there could be others that are farther away.
The discovery of the exoplanet Wolf 1069 b confirms that red dwarfs need to be studied to look for potentially habitable planets. They are the most common and, even if most of them are too active to have planets capable of hosting life forms similar to the Earth’s ones, the search for interesting planets continues together with the studies of the ones found so far.
