Can planets orbiting M dwarf stars become habitable, or does the star’s activity prevent it? This is what a recent study published in The Astronomical Journal hopes to address as a team of researchers investigated a potentially habitable exoplanet orbiting an M dwarf star. This study has the potential to help scientists better understand planets orbiting M dwarf stars, as the latter have been observed to have such extreme solar activity that could strip planetary atmospheres, thus making them uninhabitable.
For the study, the researcher analyzed the recently discovered GJ 12 b, which is located approximately 40 light-years from Earth with an orbital period of approximately 13 days and an equilibrium (baseline) temperature of approximately 300 Kelvin (~ 27 degrees Celsius/80 degrees Fahrenheit). For context, Earth’s equilibrium temperature is 255 Kelvin (~18 degrees Celsius/0 degrees Fahrenheit). Additionally, its radius is just under Earth’s radius and orbits just inside the inner edge of the star’s habitable zone.
The goal of this study was to ascertain GJ 12 b’s mass and eccentricity, which the researchers found to be approximately 0.7 Earth and 0.24, respectively. However, the team quickly noted that GJ 12 b might not have an eccentric orbit. For context, Earth’s eccentricity is 0.0167, or almost a perfect circle.
The study notes, “GJ 12 b’s mass results in a planetary density comparable to or less dense than that of Earth, possibly indicating the presence of water or a low bulk iron mass fraction. With its low mass, GJ 12 b is likely within reach of JWST transmission spectroscopy observations, making it an excellent target for determining the location of the cosmic shoreline. Its low mass may mean that the planet could have trouble retaining its primary atmosphere during the star’s active pre-main-sequence phase. However, if it has a heightened eccentricity, it may be able to sustain a secondary atmosphere through tidally induced volcanism.”
This study comes as M dwarf stars are increasingly becoming new targets for habitable worlds, specifically with the TRAPPIST-1 system and its seven rocky exoplanets. However, scientists have observed the solar activity of that star is so strong that it could potentially be stripping the atmospheres of its exoplanets. Therefore, studies like this demonstrate that while M dwarf stars are compelling targets, caution should be practiced regarding their habitability.
What new insights about GJ 12 b will researchers make in the coming years and decades? Only time will tell, and this is why we science!
As always, keep doing science & keep looking up!
Sources: The Astronomical Journal, NASA, Wikipedia
Featured Illustration Credit: NASA/JPL-Caltech/R. Hurt (Caltech-IPAC)