The K2-18B exoplanet generates newspaper heads because researchers have announced what the proof of life could be on the planet. The JWST detected a few atmospheric chemicals produced on earth by living organisms, reports Universetoday.com.
The astronomers responsible for the results are quickly reminded of everyone that they have not found life, only chemicals that can indicate the presence of life. However, the results raise a greater question: will the JWST really ever detect life?
The JWST has been developed with four overarching science themes, and one of them is planetary systems and the origin of life. Early design documents and scientific articles developed this theme, although they were careful with predicting what the telescope would think.
Much of writing acknowledged that the JWST would have difficulty identifying definitive biosa signatures. Instead, the telescope was characterized as an intermediate step between the Hubble and the Spitzer, and future telescopes that could reliably detect biosignatures.
In a new article, the well-known planetary scientist Sara Seager from MIT and its co-authors from the US, the UK and Europe remind us of how difficult it is for the JWST to provide definitive proof of life on distant exoplanets. The paper is entitled “Prospects for detecting signs of life on exoplanets in the JWST era” and will be published in the procedure of the National Academy of Sciences.
“The search for signs of life in the universe has entered a new phase with the arrival of the James Webb Space Telescope (JWST),” the authors write. “Detecting biosignature gases via exoplanet -atmosphere transmission spectroscopy is in principle within the reach of JWST.” The question is, how reliable are those detections? Are public expectations from the row with the actual possibilities of the telescope?
Final evidence for life on a distant exoplanet such as K2-18B would never jump up and announce itself. That planet is about 125 light years away. Planetary atmospheres are complex and the great distance makes them more difficult.
Transmission spectroscopy is a powerful tool, but it stands for major challenges. The light of the star can pollute spectroscopic results and the collection of data is difficult. For these reasons and others, Seager and her colleagues suggest that we are leaving the idea of detecting an atmospheric “silver bullet” that reveals the presence of life.
Instead, the most important contribution of the JWST is to build a more extensive understanding of exoplanets and their atmospheres. “The characterization of rocky or sub-size-sexoplaneten with JWST is a complicated task and moves us away from the idea of finding a definitive ‘silver bullet’ biosignature gas,” the authors write.
One of the difficulties with which the JWST is confronted in transmission spectroscopy of rocky and sub-septune-size planets is that it is really only suitable for planets that run in a job around dwarfs (red dwarfs). Because these stars are smaller, the signal of implementing exoplanets is more easily detected, while larger, brighter stars can introduce a lot of noise in planetary transit signals.
“Since m dwarf stars are half to a tenth of the size of our sun, the TS (transmission spectroscopy signal) will have signals 4 to 100 times larger than zodiacutters,” the authors explains.
However, M -dwarfs form their own challenges.
The problem is that M-dwarfs tend to be more active than star big stars. “Their stellar magnetic activity, higher than for solar-type stars, manifests itself as starspots, faculae and torches that contaminate the spectra,” the authors write. They mention that in the well-known Trappist-1 system the M Dwarf star pollutes and overwhelms the transmission spectra.
The authors remind us how difficult it is to take a transmission spectroscopy signal and to draw concrete conclusions about its meaning. “It may seem like a piece to use spectra to determine planetary properties (atmosphere, survival, surface and interior bulk composition, habitability and presence of life, and more).
After all, observed exoplanet spectra represent a very average signal of complex 3D-physical and chemical atmospheric processes, reduced to relative changes in the observed wavelength dependence of the combined star and planet light as a point source, “she explains.
Interpreting transmission spectroscopy signals is not easy. We are still in the early stages of this kind of science and researchers will only get better at it. Seaver and its co-authors explain that there are three criteria to determine whether a biosignature detection is reliable:
1. Detection: Is the signal robust?
2. Attribution: Are the spectral functions correctly attributed to the correct gas (ES)?
3. Interpretation: How reliable are the derivative planetary properties?
According to the authors, the provisional detection of DMS and/or DMDs does not meet all three of these criteria.
“The example of the preliminary detection of DMs in the atmosphere of K2-18 B is the first meeting of the exoplanet community with a gas care of biosignature-one claim that not all three of the most important criteria above fail,” they write.
The authors do not chop words in their conclusion: “We conclude with the sobering realization that we might never be able to discover the discovery of a Biosignature gas in an exoplanet -atmosphere atmosphere.”
Scientists, however, make progress and the JWST is an important tool for effort. By gaining more observations and data, it contributes to a better understanding of exoplanets and their atmospheres. Astronomers will continue to find candidates for biosignature in exoplanet -atmospheres, and any detection will contribute to their knowledge.
“In the coming years, JWST will remain the flagship of this era of discovery and will be remembered as the first telescope to take the first concrete steps to answer the question: are we alone?”
