The James Webb Space Telescope (JWST) has identified an exoplanet, TOI-561 b, that challenges current planetary formation models. This super-Earth, located 280 light-years away in the constellation Sextans, possesses a surprisingly thick atmosphere despite orbiting extremely close to its star. The discovery suggests that planets can form and retain atmospheres in conditions previously considered inhospitable, forcing astronomers to re-evaluate prevailing theories.
A Scorching, Tidally Locked World
TOI-561 b is roughly 1.4 times the size of Earth and completes an orbit around its star in just 11 hours. This rapid orbit places it in the category of ultra-short period exoplanets, orbiting at 1/40th the distance between Mercury and the sun. As a result, the planet is tidally locked: one side perpetually faces its star, creating a permanent dayside and nightside.
The Atmospheric Anomaly
The most striking feature of TOI-561 b is its atmosphere. Based on its proximity to its star, the planet’s dayside temperature should reach up to 4,900°F (2,700°C) if it were a bare rock surface. However, JWST measurements show a temperature of just 3,200°F (1,800°C). This discrepancy suggests the presence of a dense atmosphere shielding the surface and redistributing heat.
Why this matters: Planets in such close orbits are usually stripped of their atmospheres over billions of years due to stellar radiation. TOI-561 b’s atmospheric retention defies this expectation, indicating that planets can sustain atmospheres even in extreme environments.
Unusual Composition and Formation
The planet’s low density also presents a puzzle. TOI-561 b orbits an old, iron-poor star in the Milky Way’s thick disk, suggesting it formed in a chemically distinct environment from our solar system’s planets. The atmosphere likely contains volatile compounds, such as water vapor and silicate clouds, which contribute to efficient heat distribution and starlight reflection.
Researchers believe that strong winds carry heat from the dayside to the nightside. The atmosphere also absorbs near-infrared light, further lowering the measured temperature.
“We really need a thick volatile-rich atmosphere to explain all the observations,” says astronomer Anjali Piette, highlighting the necessity of an unusual atmospheric composition to account for the data.
The findings, published in The Astrophysical Journal Letters on December 11, underscore JWST’s ability to detect previously undetectable planetary characteristics. The discovery of TOI-561 b raises fundamental questions about planetary formation and atmospheric retention.
This planet proves that the universe is full of surprises and that our understanding of exoplanetary systems remains incomplete. Future observations will be crucial to unraveling the mysteries of this “hell planet” and refining our models of how planets evolve in extreme conditions.
