We now know that our nearest neighbor, Proxima Centauri, hosts at least two planets. But we’re not sure if there are any planets in the vicinity of Alpha Centauri, a binary system just outside it. If there are, we now know what they might look like. New research has used modeling and spectroscopic data from the system’s two stars to estimate what a rocky planet in the system’s habitable zone might consist of.
To estimate the composition of this hypothetical planet called Cent-Earth, the team developed what they call a devolatilization model. To begin with, they looked at the amounts of volatile (hydrogen, carbon, oxygen, etc.) and non-volatile elements (such as iron and silicon) in the sun and Earth and how they differed from each other.
Armed with this data, the team then looked at high-resolution spectroscopy data on the elements in the Centauri A and α Centauri B stars, which provided them with information about 22 elements. Based on their model and this data, they were able to estimate possible compositions of a hypothetical rocky planet in the system’s habitable zone. “You get a model of the chemical makeup of rocky planets that would be in the habitable zone,” Charley Lineweaver, one of the authors of the paper, told Ars.
Show me what you’re made of
It is likely that α-Cen-Earth – if it exists – would be geochemically similar to Earth, with a mantle likely dominated by silicates. But it can contain more graphite and diamond, according to Lineweaver, thanks to a higher ratio of carbon to oxygen.
The planet’s water storage capacity would also be comparable to Earth’s core, but it would also have lower geological activity — possibly no plate tectonics at all — and a smaller iron core. “The planet that emerges from it will be interestingly different in terms of mineralogy and the abundance of rock versus, say, methane and carbides, graphite and maybe even diamonds in the core,” Lineweaver said.
According to Lineweaver, the model could also be applied to other hypothetical planets. He added that he personally suspects rocky planets are much more common in other solar systems than we’ve discovered so far — it’s not so much that they aren’t there, it’s just that our ability to detect them is somewhat limited.
However, it is possible that α-Cen-Earth – or another planet – is different from the model, as meteors carrying other elements often impact planets, potentially affecting their overall chemical composition. However, the team’s model could help researchers identify habitable planets in the future, Lineweaver said.
The Astrophysical Journal, 2022. DOI: 10.3847/1538-4357/ac4e8c (About DOIs)
