An analysis led by astronomer Diana Kossakowski from the Max Planck Institute for Astronomy has found a rocky planet similar to our own that orbits its parent star, the red dwarf Wolf 1069, in the habitable zone.
The planet, named Wolf 1069b, has a mass similar to Earth ‘s, is very likely rocky and could also have an atmosphere. This makes the planet one of the few promising targets for the search for signs of favorable conditions for life and biological signatures.
The search for exoplanets
When astronomers search for planets outside our Solar System, they are particularly interested in planets similar to our own. Of the over 5,000 exoplanets discovered so far, only a dozen have a mass similar to Earth’s. This small group are located in the habitable zone, the zone of a planetary system where water could be in a liquid state on the surface. With Wolf 1069b, the number of these exoplanets on which life could have evolved has increased by one candidate.
Detecting planets of such small mass is still very challenging. Diana Kossakowski and her team took on this complex task. Within the Carmenes Project, a specific tool for the search for potentially habitable worlds was developed. The Carmenes team is using this apparatus at the Calar Alto Observatory in Spain.
“When we analyzed the data of the Wolf 1069 star, we discovered a clear low-amplitude signal of what appears to be a planet of about Earth mass” says Kossakowski. “It orbits the star in 15.6 days at a distance equivalent to one-fifteenth of the separation between Earth and the Sun“ the results of the study were published in the journal Astronomy & Astrophysics (ref.).
Characteristics of Wolf 1069b
According to the study, the surface of the red dwarf star is relatively cool and thus appears orange-red. Despite its close distance to the central star, the planet Wolf 1069b therefore receives only about 65% of the incident radiant power that Earth receives from the Sun. These special conditions make planets around red dwarf stars like Wolf 1069 potentially friendly to life.
In addition, they may all share another special property. Their rotation is probably locked in a tidal manner to the orbit of its host star. In other words, the star is always facing the same side of the planet. So there is eternal day on one side, while the other side is always night.
If Wolf 1069b is assumed to be a barren and rocky planet, the average temperature even on the side facing the star would be just below 23°C. According to existing knowledge, it is possible that Wolf 1069b has an atmosphere. Based on this assumption, its temperature could be greater than 13°, as shown by computer simulations with climate models. In these circumstances, water would remain liquid and conditions favorable to life might prevail.
The Importance of the Magnetic Field
The atmosphere is not the only prerequisite for the emergence of life. It is also important to protect against high-energy electromagnetic radiation, particles that would destroy possible biomolecules. The radiation and particles come from interstellar space or the central star. If the radiation from the star is too intense, it can also strip away the atmosphere of a planet, as happened with Mars. The red dwarf, Wolf 1069 emits only relatively weak radiation.
So, an atmosphere could have been preserved on the newly discovered planet. And it is also possible that Wolf 1069b has a magnetic field that protects it from charged particles from the stellar wind. Many rocky planets have a liquid core, which generates a magnetic field through the dynamo effect, as on the planet Earth.
At a distance of 31 light-years, Wolf 1069b is the sixth most Earth-mass planet closest to us, in the habitable zone around its host star. It belongs to a small circle, such as Proxima Centauri b and Trappist-1e, which are candidates for biosignature searches. However, such observations are currently beyond our capabilities in astronomical research. “We probably have to wait another ten years for this” emphasizes Kossakowski. The Extremely Large Telescope (ELT), currently under construction in Chile, could be capable of studying the composition of the atmospheres of those planets and perhaps even detecting molecular evidence of life.