This August’s thrilling discovery of an Earth-like, potentially habitable rocky world in the star system closest to our own sent shockwaves through the scientific community. Now, a new study has concluded that Proxima b is likely to be an ocean world blanketed by a thin atmosphere.
The discovery was made by a team of astronomers and astrophysicists from France’s National Center for Scientific Research (CNRS).
“The planet may very well host liquid water on its surface, and therefore also some forms of life,” a statement from CNRS read. “The planet could be an ‘ocean planet’, with an ocean covering its entire surface, and similar water to some icy moons around Jupiter or Saturn.”
Although it was always seen as a possibility that the world contained surface water, scientists can only use mathematical models to make these kinds of predictions until it transits across the star – allowing researchers to study its atmospheric composition. And, although Proxima b's year length is 11.2 days, we've yet to see a transit and we're not sure we ever will.
So instead, using a compilation of the most up-to-date data, best-guess estimates, and computer simulations, this team worked out the most likely distribution of mass within Proxima b. According to a peer-reviewed paper uploaded to arXiv, they calculated that its radius was between 0.94 and 1.4 times that of Earth’s. At the lower estimate, it would contain a very dense metallic core, one that makes up two-thirds of its mass.
It would also be surrounded by a rocky mantle, just like Earth’s. Comparing this to many other rocky planets and exoplanets, the team estimated that if there is surface water, it would not make up more than 0.05 percent of Proxima b’s total mass, which is again very similar to our own pale blue dot.
At the higher radius estimate, its mass would be split 50-50 between a rocky center and surrounding ocean. In this case, the world would be covered by a global ocean 200 kilometers (124 miles) deep.
Either way, some sort of ocean is highly likely. Significantly, both simulations also indicate a thin atmosphere would also be present.
These are merely hypotheses at the moment; it is also possible that this rocky world is barren, dry, and lifeless. However, evidence is certainly mounting that a second home to humanity could indeed be hiding right around the corner.
"It is likely to harbor liquid water at its surface and therefore to harbor life forms," said the statement.
Image in text: Comparing the composition of other exoplanets to possible configurations for Proxima b, using radius (y axis) and mass (x axis). It's most likely that it is either very much like Earth, or that it has a global ocean making up far more of its mass. CNRS
An artist's impression of Proxima b, featuring nearby stars Alpha Centauri A and B, seen close together to the top-right of Proxima Centauri, the host red dwarf star. ESO/M. Kornmesser