This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: In the search for extraterrestrial life, it makes sense to first look for rocky planets with an atmosphere, like Earth. Without an atmosphere, a planet can't have surface water.
But of the more than 6,300 exoplanets cataloged thus far, the vast majority are not rocky, and only a handful of the rocky worlds appear to have an atmosphere. In a study published in The Astrophysical Journal Letters, a group led by University of Chicago scientist Brandon Park Coy reports another: a rocky super-Earth 154 light-years away in the constellation Pisces. Named HD 3167 b, this very hot "lava world" zips around its host star in just one Earth day.
"What's so surprising is that the closer a rocky planet orbits its star, the harder it should be to have an atmosphere, because it's bombarded by stellar wind and gets more high-energy photons from the star. But it seems that many of these lava worlds do," explained Edwin Kite, UChicago associate professor of geophysical sciences and co-author of the study. "These planets are too hot for life, but by studying them, we can say something about the processes that matter for other rocky worlds." In the Q&A below, Coy, a graduate student in Kite's group and first author of the study, describes why atmospheres on so-called lava worlds matter, how they found this one and next steps.
One of the driving questions that the James Webb Space Telescope is being used to answer is whether planets orbiting stars much smaller than the sun have atmospheres. It appears that most of those terrestrial planets don't—they're just bare rock. But surprisingly, we've found evidence that the majority of lava worlds—similar in composition to Earth and Venus but much, much hotter—might have atmospheres.
Five terrestrial planets found with atmospheres, including the one described in this study, have been ultra-hot. This planet, however, is the coolest lava world found so far with evidence of an atmosphere. This is interesting because we're trying to understand the temperature transition between planets with and without atmospheres.
The result is the first from a program led by Megan Weiner Mansfield, PhD'21, who's now at the University of Maryland. The goal of the program, which is looking at 10 ultra-hot lava worlds, is to see if there's a critical temperature above which you start seeing planets with atmospheres. "We're interested in studying these kinds of planets because we think early Earth might have looked a lot like a lava world," said Coy.
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