Posted by Astronomers have found strong evidence that HD 3167 b, a rocky super-Earth about 154 light-years away in the constellation Pisces, retains an atmosphere despite orbiting extremely close to its star.
The planet completes an orbit in roughly one Earth day and belongs to a class of worlds known as lava planets, whose star-facing surfaces may contain molten rock. The study, published in The Astrophysical Journal Letters, adds HD 3167 b to the small number of rocky exoplanets with evidence for atmospheres.
This is particularly surprising because planets orbiting so close to their stars experience intense stellar radiation and winds capable of stripping atmospheres away. Yet several ultra-hot rocky worlds studied so far appear to have retained substantial atmospheres. Researchers investigated HD 3167 b by measuring its secondary eclipse, when the planet passes behind its star. The amount of infrared light that disappears during the eclipse reveals how much thermal radiation comes from the planet and therefore provides an estimate of its dayside temperature.
A rocky planet without an atmosphere should have an extremely hot dayside because little energy can reach its permanently dark hemisphere. An atmosphere, however, can transport heat around the planet, while clouds may reflect some incoming starlight. HD 3167 b was noticeably cooler than expected for a bare rocky surface, providing strong evidence for atmospheric heat redistribution or reflection. The planet is especially interesting because it is the coolest lava world yet found with evidence of an atmosphere. Researchers are studying a sample of ten such planets to determine whether there is a temperature threshold separating rocky worlds that retain atmospheres from those that lose them.
The composition of HD 3167 b’s atmosphere remains unknown. Although scientists previously expected lava-world atmospheres to consist mainly of vaporized rock, observations increasingly suggest that some may contain heavier volatile molecules such as carbon dioxide, carbon monoxide, or water. These worlds are far too hot to support life as we know it, but they remain important to astrobiology. Early Earth itself probably passed through a magma-ocean stage after its formation. Studying lava planets therefore offers a way to investigate atmospheric evolution on rocky worlds and understand which conditions ultimately allow potentially habitable planets to maintain atmospheres.
For more details, read the full article by University of Chicago.
