The James Webb Space Telescope has uncovered a novel type of exoplanet that significantly differs from those in our Solar System. This discovery challenges existing classifications and enhances our understanding of planetary formation and characteristics.
Astronomers have confirmed the existence of over 5,500 exoplanets orbiting stars beyond our Sun. Many of these worlds are vastly different from the planets we know, complicating the determination of their true nature. Commonly, planets fall between the sizes of Earth and Neptune, prompting debates on whether they are rocky, Earth-like worlds with thick hydrogen-rich atmospheres or icy, Neptune-like planets enveloped in water-rich atmospheres, often referred to as 'water worlds.'
However, studying these planets has been hindered by thick cloud layers that frequently obscure their lower atmospheres, leaving much of their nature a mystery.
An international team of researchers led by Everett Schlawin from the University of Arizona and Kazumasa Ohno from the National Astronomical Observatory of Japan utilized the James Webb Telescope to peer through clouds at an exoplanet known as GJ 1214 b. Located just 48 light-years from the Solar System in the constellation Ophiuchus, GJ 1214 b is one of the easiest examples to study.
Instead of a hydrogen-rich super-Earth or a water world, new data revealed carbon dioxide (CO2) concentrations comparable to those found in the dense CO2 atmosphere of Venus in our Solar System. Nevertheless, uncertainties remain regarding the new findings.
'The CO2 signal detected from the initial study is faint and therefore required careful statistical analysis to ensure its authenticity,' Ohno explained.
'At the same time, we needed physical and chemical knowledge to extract the true nature of GJ 1214 b's atmosphere from Schlawin’s study,' he added.
Ohno then employed theoretical models to run a multitude of 'what if' scenarios about the planet's atmosphere. Among all these models, those that best fit the data suggest an atmosphere dominated by carbon, akin to a 'super-Venus.'
Despite its intriguing nature, the detected atmospheric signature is very faint. Everett Schlawin likened the identified data to reading a book.
'It is equivalent to Leo Tolstoy's War and Peace. If I gave you two copies and changed one sentence in one of the books, could you find that sentence?' he remarked.
The team emphasizes the necessity for future studies to confirm and expand their findings regarding this common yet mysterious type of exoplanet.