Molten World TOI-561 b Challenges Exoplanet Theories with Surprisingly Thick Atmosphere
Table of Contents
A rocky exoplanet cloaked in vaporized rock and boasting a surprisingly persistent atmosphere is challenging existing theories about planetary formation and atmospheric retention. New research, led by scientists at Carnegie Science, focuses on TOI-561 b, an “ultra-hot super-Earth” exhibiting characteristics that defy conventional astrophysical understanding.
A Hellscape Billions of Years in teh Making
TOI-561 b orbits its star at a distance of less than 1.6 million kilometers (0.99 million miles) – just one-fortieth the distance between the Sun and Mercury. This incredibly tight orbit results in a tidally locked world, with one side perpetually facing its star and the other plunged into eternal darkness. Despite the intense radiation, the planet has somehow managed to retain a substantial atmosphere for billions of years, a phenomenon that has puzzled researchers.
“Based on what we know about other systems, astronomers would have predicted that a planet like this is too small and hot to retain its own atmosphere for long after formation,” explains a Carnegie science astronomer.
unveiling the Secrets of an Ancient World
The exoplanet, categorized as an ultra-short period (USP) planet due to its orbit of less than 11 hours, is approximately twice the mass of Earth and 1.4 times its radius. It circles an ancient star – around 10 billion years old,more than twice the age of our Sun – located in the Milky way’s thick disk.This star is notably low in iron and rich in elements like oxygen, magnesium, and silicon, suggesting it formed in the early Universe when these elements were more abundant.
Researchers initially found TOI-561 b’s low density – roughly four times denser than water – perplexing.This could be attributed to a small iron core and rocks less dense than those found in Earth’s crust, consistent with its age and the elemental composition of its star.Though, the presence of an atmosphere could also contribute to the apparent lower density.
JWST Data Confirms Atmospheric Presence
To determine the cause of the low density, the team turned to the James Webb Space Telescope (JWST), analyzing data collected over 37 hours and nearly four complete orbits of the planet.By measuring the dayside brightness in near-infrared light using Webb’s NIRSpec instrument, they were able to calculate the planet’s temperature.
Without an atmosphere, TOI-561 b would be expected to reach a scorching 2,700 degrees Celsius (4,900 degrees Fahrenheit). Though, measurements revealed a cooler temperature of around 1,800 degrees Celsius, strongly indicating the presence of a thick, volatile-rich atmosphere.
How Does TOI-561 b Retain Its Atmosphere?
the persistence of the atmosphere is the central mystery. Researchers theorize that an equilibrium exists between the atmosphere and a global magma ocean covering the planet’s surface.Without an atmosphere, the nightside would likely freeze solid. Instead, gases released from the planet’s crust replenish the atmosphere, while the magma ocean may act as a sink, drawing gases back into the planet’s interior.
The planet’s iron content may also play a crucial role, possibly trapping volatile chemicals within the magma ocean or core. One study suggests that planets with high irradiation temperatures can replenish their atmospheres faster than they are lost.
“From the sample of rocky planets with dayside brightness temperature constraints, it truly seems planets with irradiation temperatures exceeding ∼2000 K are able to replenish volatile envelopes faster than they are lost,” the researchers write in their paper, published in The Astrophysical Journal Letters.
Pinpointing the exact mechanisms behind TOI-561 b’s atmospheric retention will require further inquiry,but this revelation offers a compelling new viewpoint on the diversity and resilience of exoplanets.
