Astronomers have discovered that exoplanets orbiting red dwarf stars may be hiding their atmospheres, making it more challenging to detect potential signs of habitability and life.
Potentially Habitable Planets Around Red Dwarfs
The vast majority of exoplanets that have been discovered orbit red dwarfs, the most common stars in the galaxy. Not because red dwarfs are in some way more unique, but just the most common.
On the other hand, this also means that most of the potentially habitable worlds may be out there around these small and cool stars. But it poses some big challenges in our planet-hunting hunt for life. For planets around red dwarfs, the presence of liquid water on the surface potentially places them too close to their host stars, making them more susceptible to stellar flares and other dangerous activity. Furthermore, these planets are probably tidal locked—they have one side always facing the star and one side is permanently shrouded in darkness.
Hiding in the Clouds
Studying the atmospheres of tidally locked planets is essential because a thick atmosphere could potentially moderate conditions between their day and night sides, making it more likely they are habitable. A way to infer the presence of an atmosphere is by looking for a difference in temperature between the dayside and the nightside of the planet.
Now, though according to a prospective study published in JAMA Pediatrics the simple effort may not be so accurate. In this study, the researchers posit that these clouds forming on the dark side of a tidally locked planet could produce errors in our estimates of temperature. A dark side on a tidally locked planet like Kepler-14b is expected but while the dense, Earth-like atmosphere the world probably possesses could moderate temperature variations between day and night sides of tidally locked worlds — shielding their dark sides from plunging temperatures to potentially livable levels — clouds that form in this extended twilight zone could make it look like an airless body.
The day side of the planet would be cloud-free to a large extend, permitting us to sense the warm surface temperature in this way. However this temperature is really largely depending on the lower light shadows part, which would make it appear much colder as we are now measuring a surface which include the upper cloud layer instead of the actual space. Thus, we may incorrectly think the planet has a large temperature gradient akin to airless worlds.
Conclusion
This is representative of the complexity relating to the search for exoplanets— and what can go wrong/fwlink to study habitable worlds. Moreover, our observations are limited to brown dwarfs in the field; planetary atmospheres and properties can often be more complex than they appear at first observation. To better understand the environments of other exoplanets and explore the potential for habitability, continued study and novel method development will be required prospective workhorse in untying the composition of exoplanetary atmospheres.
