A protective atmosphere, a welcoming sun, and abundant liquid water make Earth a remarkable place. Leveraging the extraordinary capabilities of the NASA/ESA/CSA James Webb Space Telescope, astronomers are on a mission to uncover just how unique and extraordinary our planet truly is. Is it possible for a temperate environment to exist elsewhere, perhaps around a different type of star? The TRAPPIST-1 system offers an intriguing opportunity to explore this question, as it contains seven Earth-sized planets orbiting red dwarf stars—the most common type in the Milky Way.
The artist’s concept depicts TRAPPIST-1d passing in front of a turbulent star, showing the other planets in the background. Image credits: NASA/ESA/CSA/Joseph Olmsted, STSCI.
TRAPPIST-1 is a super cool dwarf star situated 38.8 light-years away in the constellation Aquarius.
These stars are slightly larger than Jupiter, comprising only 8% of our Sun’s mass. They rotate quickly and emit UV energy flares.
TRAPPIST-1 is home to seven transiting planets designated TRAPPIST-1b, c, d, e, f, g, and h.
All these planets are similar in size to Earth and Venus, or marginally smaller, with very brief orbital periods of 1.51, 2.42, 4.04, 6.06, 9.21, 12.35, and 20 days, respectively.
They may all be tidally locked, meaning the same side always faces their star, akin to how the same side of the moon is always turned towards Earth. This results in a permanently night side and a permanently day side for each TRAPPIST-1 planet.
“Ultimately, we aim to discover whether similar environments to those we enjoy on Earth exist elsewhere, and under what conditions they might thrive,” stated Dr. Caroline Piaulett Graeb, an astronomer at the University of Chicago and the Trottia Institute for Planetary Research.
“At this stage, we can exclude TRAPPIST-1d as a potential twin or cousin of Earth, even as Webb enables us to investigate Earth-sized planets for the first time.”
Dr. Piaulet-Ghorayeb and her team utilized Webb’s NIRSpec (near-infrared spectroscopy) instrument to capture the transmission spectra of the TRAPPIST-1d planet.
They found no common molecules typically present in Earth’s atmosphere, such as water, methane, or carbon dioxide.
However, they have outlined several possibilities for the exoplanet that warrant further investigation.
“There are multiple reasons we might not detect an atmosphere around TRAPPIST-1d,” Dr. Piaulet-Ghorayeb mentioned.
“It may have a very thin atmosphere, similar to Mars, which is challenging to identify.”
“Alternatively, thick, high-altitude clouds may obscure certain atmospheric signatures.”
“Or it could be a barren rock with no atmosphere whatsoever.”
In any case, TRAPPIST-1d faces challenges as a planet orbiting a red dwarf star.
TRAPPIST-1, the host star of the system, is known for its volatility and often emits high-energy radiation flares that can strip away the atmosphere of nearby small planets.
Nevertheless, scientists remain eager to search for atmospheric signs on the TRAPPIST-1 planets, as red dwarfs are the most prevalent stars in our galaxy.
If these planets can retain an atmosphere here, it suggests they could potentially do so anywhere, even under the harsh conditions of stellar radiation.
“Webb’s sensitive infrared instruments allow us to probe into the atmospheres of these small, cold planets for the first time,” said Dr. Bjorn Beneke, an astronomer at the Institute for Planetary Research at Montreal University.
“We are using Webb to identify atmospheres on Earth-sized planets and define the thresholds between those that can and cannot sustain an atmosphere.”
Results will be published in Astrophysical Journal.
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Caroline Piaulett Graeb et al. 2025. Restrictive conditions on the potential secondary atmosphere of the temperate rocky exoplanet TRAPPIST-1d. APJ 989, 181; doi:10.3847/1538-4357/ADF207
Source: www.sci.news
