TRAPPIST-1 is one of the most promising places to study Earth-like planets outside our solar system. Among its seven rocky worlds, planet e is fascinating. If it has an atmosphere, scientists believe it could have liquid water on its surface, a key ingredient for life as we know it.
Scientists recently used the JWST’s NIRSpec PRISM instrument to study the atmosphere of TRAPPIST-1 e for the first time. However, they found that light from the star interfered with the data, called stellar contamination, and this interference changed across the four observations.
Néstor Espinoza of the Space Telescope Science Institute in Baltimore, Maryland, a principal investigator on the research team said, “Webb’s infrared instruments are giving us more detail than we’ve ever had access to before, and the initial four observations we’ve been able to make of planet e are showing us what we will have to work with when the rest of the information comes in.”
Although scientists have only studied TRAPPIST-1 e during four transits so far, they’re confident the planet no longer has its original hydrogen-helium atmosphere. That’s likely because TRAPPIST-1 is a very active star, and its frequent flares could have stripped away that lightweight layer over time.
Many planets, including Earth, can form a heavier secondary atmosphere after losing their primary one. It’s possible TRAPPIST-1 e never developed this second atmosphere, or it might still have one. Researchers say both possibilities are equally likely.
To explore this further, the team created new methods to analyze data from the James Webb Space Telescope and better understand what kind of atmosphere and surface conditions the planet might have.
Scientists believe it’s unlikely that TRAPPIST-1 e has an atmosphere dominated by carbon dioxide, like the thick clouds of Venus or the thin air of Mars. But they also caution that we shouldn’t expect a perfect match with any planet in our solar system, TRAPPIST-1 e may be something entirely different.
Team member Nikole Lewis, an associate professor of astronomy at Cornell University, said, “TRAPPIST-1 is a very different star from our Sun, and so the planetary system around it is also very different, which challenges both our observational and theoretical assumptions.”
Scientists reports new findings of TRAPPIST-1 planetary system
“If there is liquid water on TRAPPIST-1 e, it would be accompanied by a greenhouse effect, in which various gases, particularly carbon dioxide, keep the atmosphere stable and the planet warm.”
“A little greenhouse effect goes a long way, and the measurements do not rule out adequate carbon dioxide to sustain some water on the surface.”
According to scientists, water on TRAPPIST-1 e could either cover the entire planet as a global ocean or exist only on the side that always faces the star, surrounded by ice. This is possible because the planet is likely tidally locked.
Researchers led by Néstor Espinoza and Natalie Allen are conducting 15 new observations of TRAPPIST-1 e using the James Webb Space Telescope with a strategic twist. They’re timing the telescope to catch planet b and planet e transiting the star back-to-back.
Why this matters: Planet b, the closest to the star, is believed to be a bare rock with no atmosphere. So, any signals during its transit are likely coming only from the star itself.
Since planet e transits right after, scientists can use planet b’s data as a stellar baseline. By comparing the two, researchers can filter out the star’s interference and focus on what’s unique to planet e. If certain chemicals appear only in planet e’s spectrum, it’s strong evidence they belong to its atmosphere, if it has one.
Ana Glidden, a post-doctoral researcher at Massachusetts Institute of Technology’s Kavli Institute for Astrophysics and Space Research, who led the research on possible atmospheres for planet e said, “We are really still in the early stages of learning what kind of amazing science we can do with Webb. It’s incredible to measure the details of starlight around Earth-sized planets 40 light-years away and learn what it might be like there, if life could be possible there. We’re in a new age of exploration that’s very exciting to be a part of.”
Journal Reference:
- Néstor Espinoza, Natalie H. Allen, Ana Glidden, Nikole K. Lewis, Sara Seager, Caleb I. Cañas, David Grant, Amélie Gressier, Shelby Courreges, Kevin B. Stevenson et al. JWST-TST DREAMS: NIRSpec/PRISM Transmission Spectroscopy of the Habitable Zone Planet TRAPPIST-1 e. The Astrophysical Journal Letters. DOI 10.3847/2041-8213/adf42e
- Ana Glidden, Sukrit Ranjan, Sara Seager, Néstor Espinoza, Ryan J. MacDonald, Natalie H. Allen, Caleb I. Cañas, David Grant, Amélie Gressier, Kevin B. Stevenson et al. JWST-TST DREAMS: Secondary Atmosphere Constraints for the Habitable Zone Planet TRAPPIST-1 e. The Astrophysical Journal Letters. DOI 10.3847/2041-8213/adf62e
