Astronomers have investigated the atmosphere and potential habitability of a famous “Goldilocks zone” planet using NASA’s powerful James Webb Space Telescope (JWST).
The planet in question is TRAPPIST-1e, an Earth-sized rocky exoplanet that’s located around 40 light-years away from our planet.
TRAPPIST-1e is the fourth planet in orbit around a red dwarf star called TRAPPIST-1. It sits well within the “habitable zone” or Goldilocks zone, the region of space around a star that is neither too hot nor too cold to allow liquid water to exist on the surface of a planet.
However, just existing in the habitable zone of a star isn’t sufficient to guarantee the existence of liquid-water oceans or indeed the conditions needed to support life. After all, Earth, Mars, and Venus are all in our solar system’s habitable zone, but only one of these planets has water oceans and supports life today (as far as we know). One of the key differences is the atmosphere of our planet, and that is what astronomers are searching for around TRAPPIST-1e.
“TRAPPIST-1e has long been considered one of the best habitable zone planets to search for an atmosphere,” study team member Ryan MacDonald, a researcher at the University of St. Andrews in Scotland, said in a statement. “But when our observations came down in 2023, we quickly realized that the system’s red dwarf star was contaminating our data in ways that made the search for an atmosphere extremely challenging.”
The JWST data indicate several possible scenarios for TRAPPIST-1e and its potential atmosphere. That makes this research a significant step forward in the search for life beyond the solar system.
To examine the potential atmosphere of TRAPPIST-1e, the team had to wait until it crossed or “transited” the face of its parent star. This reveals details of the chemical composition of a planet’s atmosphere because chemicals absorb light at characteristic wavelengths. That means when starlight passes through a planetary atmosphere, the chemicals in that atmosphere leave their characteristic “fingerprints” in the spectrum.
This isn’t as straightforward as it may initially sound. Astronomers have to account for factors like starspots across the face of the red dwarf star. So the team has spent the last year carefully removing contamination from the TRAPPIST-1e data to hone in on the planet’s atmosphere, or lack thereof.
“We are seeing two possible explanations,” MacDonald said. “The most exciting possibility is that TRAPPIST-1e could have a so-called secondary atmosphere containing heavy gases like nitrogen. But our initial observations cannot yet rule out a bare rock with no atmosphere.”
The indeterminate nature of the team’s results means that JWST is far from finished with TRAPPIST-1e. The researchers hope to perform a deeper search for the planet’s atmosphere, with each subsequent transit potentially presenting a clearer picture of its atmospheric contents.
“In the coming years, we will go from four JWST observations of TRAPPIST-1e to nearly 20,” MacDonald concluded. “We finally have the telescope and tools to search for habitable conditions in other star systems, which makes today one of the most exciting times for astronomy.”
The team’s research was published as two papers on Monday (Sept. 8) in The Astrophysical Journal Letters
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