An astronomical object once presumed to epitomize one of the galaxy’s most prevalent categories of planets has instead unveiled itself as an entirely unprecedented phenomenon.

The exoplanet Enaiposha, also designated as GJ 1214 b, orbits a red dwarf star situated approximately 47 light-years from our home planet. Initially categorized as a mini-Neptune, comprehensive observations conducted using the James Webb Space Telescope (JWST) now indicate that this exoplanet bears a closer resemblance to Venus—albeit on an immense scale.

This revelation has given rise to a novel classification that astronomers have termed ‘Super-Venus’.

Enaiposha ranks among the most extensively scrutinized exoplanets known to humanity. Discovered in 2009, its mass and radius suggest a position between Earth and Neptune, further confirmed by observations revealing a significantly substantial atmosphere.

Within this particular mass regime, exoplanets predominantly fall into two categories. Super-Earths are theorized to be terrestrial planets larger than Earth, typically possessing hydrogen-rich atmospheres, if any. In contrast, mini-Neptunes, which may exhibit similar dimensions, are characterized by their significantly denser atmospheres, abundant in hydrogen and helium, potentially enveloping liquid oceans.

This lack of analogous examples in our own Solar System renders mini-Neptunes particularly intriguing, even as over 5,800 have been confirmed thus far.

While super-Earths and mini-Neptunes tantalize scientists with their potential for habitability under optimal conditions, Enaiposha, with a staggering 2.7 times the radius and 8.2 times the mass of Earth, presents a convoluted scenario. Its perilous proximity to its host star, Orkaria, renders it too inhospitable to sustain life as we know it, yet its accessibility enables us to glean insights applicable to understanding analogous worlds in the broader cosmos.

Notwithstanding its intriguing characteristics, Enaiposha is fraught with challenges. Its dense atmosphere obscures comprehensive analysis, yet recent research, leveraging JWST and Hubble observations, suggests a water-rich atmosphere interspersed with vaporized metals.

A groundbreaking study helmed by astronomers Everett Schlawin of the University of Arizona and Kazumasa Ohno from the National Astronomical Observatory of Japan has unearthed unexpected findings from transit data. As Enaiposha traversed its 1.6-day orbital path, starlight passing through its atmosphere appeared to be modified by carbon dioxide in concentrations eerily akin to the more than 96 percent present in Venus’s atmosphere.

However, the detected signal was faint.

Ohno remarked, “The detected CO₂ signal is minimal, necessitating meticulous statistical analysis to substantiate its authenticity. Simultaneously, we require in-depth physical and chemical insights to decipher the true nature of GJ 1214 b’s atmosphere.”

In a subsequent publication, the researchers endeavored to develop theoretical frameworks to elucidate the observing data. Their findings suggested that if Enaiposha possessed an atmosphere dominated by metals at lower altitudes, accompanied by relatively minor hydrogen concentrations, their model would appropriately correspond to the observations.

At elevated altitudes, the atmosphere appears laden with aerosols and CO₂, culminating in the conception of the super-Venus—a world reminiscent of Venus: exceedingly hot, enveloped by a carbon-rich atmosphere that obscures visibility.

Nevertheless, confirming these intriguing results presents its own set of challenges. The observed signatures are so diminutive that extensive, precision-focused follow-up observations are imperative to validate the research team’s conclusions, especially given the novelty of the findings.

The researchers assert the crucial nature of high-precision follow-up observations to affirm the presence of a metal-dominated atmosphere, as this could fundamentally challenge prevailing paradigms concerning the internal structures and evolutionary trajectories of sub-Neptunes.

The research has yielded two significant papers published in The Astrophysical Journal Letters, accessible here and here.