Earlier this year, the James Webb Space Telescope dashed hopes of life on one of the Earth-like exoplanets discovered in the Milky Way.
TRAPPIST-1b, a world 1.4 times the mass and 1.1 times the radius of Earth, lies just 40 light-years away, and has no detectable atmosphere to protect it from the searing radiation of its host star.
However, this result, made using mid-infrared optical observations, was not unexpected; The research was about closely studying a smaller rocky world at cooler temperatures than we normally do.
Now, there are new near-infrared spectroscopic observations from the James Webb Space Telescope—and they suggest that the behavior of the exoplanet’s host star may be interfering with our ability to make precise measurements of that exoplanet.
TRAPPIST-1b is still not habitable for life as we know it, mind you. But the discovery, led by astronomer Olivia Lim of the University of Montreal, suggests that stellar contamination could lead to false detections of molecules that have nothing to do with exoplanets.
“Our observations have shown no signs of an atmosphere around TRAPPIST-1 b. This tells us that the planet could be bare rock, have clouds high in the atmosphere or contain a very heavy molecule like carbon dioxide that makes the atmosphere so small that Undetectable.”,” says astrophysicist Ryan MacDonald From the University of Michigan.
“But what we see is that the star is definitely the biggest influence dominating our observations, and this will do exactly the same for the other planets in the system.”
The problem is that the stars are not there with uniform brightness all the time. Star spots It can cause blackout. Faculae are spots of brightness. These variations in star brightness can have an impact on spectroscopic observations of exoplanetary atmospheres.
Such observations are taken when an exoplanet passes between us and its host star. This precisely dims the star’s light. But some starlight passes through the exoplanet’s atmosphere around the edge of the planet’s disk.
Scientists can look for changes in the light spectrum as an exoplanet transits, and use these changes to look for signatures of molecules that absorb and re-emit specific wavelengths of light.
If the starlight never changed, it would be very easy. But the researchers found that stellar activity can significantly contaminate spectroscopic observations.
“In addition to contamination from star spots and facies, we saw a stellar flare, an unpredictable event during which a star appears brighter for several minutes or hours.” Lim says.
“This flare affected our measurements of the amount of light blocked by the planet. These signatures of stellar activity are difficult to model, but we need to take them into account to make sure we are interpreting the data correctly.”
The team modeled the stellar contamination, then performed two analyzes of the data: one with the stellar contamination removed, and the second with it left intact. Both results looked very similar; This means that the spectrum with TRAPPIST-1b was almost the same as the spectrum without it.
This was a confirmation of previous mid-infrared optical results that showed the exoplanet had no atmosphere. But the team’s work also showed the importance of taking stellar pollution into account before analyzing the data.
This is a good thing to discover now. The TRAPPIST-1 system contains seven exoplanets, three of which lie in the habitable zone around the star, at a nice, temperate distance, which is neither too hot nor too cold for life as we know it. The James Webb Space Telescope has not yet looked at these habitable zones, but now that we know that stellar contamination can skew results, scientists can take this into account.
“Due to the inaccuracy of stellar models.” The researchers conclude“Additional theoretical work and/or observations of the host star are necessary to provide better constraints on the contribution of stellar contamination to future transmission spectra.”
The research was published in Astrophysical Journal Letters.
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