As you read these lines, something exciting is happening; and it might change our perception of life in our Universe - no less!
Indeed, the most powerful telescope ever sent into space has now finished its commissioning phase and is starting the first cycle of its science operations. This cycle, lasting 12 months, includes observing hundreds of celestial targets of great significance from dwarf planets in our Solar System to red-shifting quasars in the deep past. To say that the James Webb Space telescope’s first year of operation is going to be a crazy time for astronomy is an understatement. Expect lots of headline news on space in the year to come.
However, what many scientists are most looking forward to will be the multiple observations by JWST of the Trappist-1 system, this 7 earth-like exoplanet system located 39 light-years away. Actually, the Trappist-1 will be the exoplanet system with the most observation campaigns assigned to it on the first observation cycle of the JWST - this gives you an idea of how important the astronomy community considers this system to be.
And, rightly so. Since its discovery in 2017, the now-famous Trappist-1 system has been the subject of numerous speculations about the possibility of extraterrestrial life due to the fact that three (!) of its exoplanets - e, f, and g - are residing within the habitable zone, the location around a star that receives just about the right amount of sunlight to allow liquid water to be present on the surface of a planetary object. Unfortunately, we know very little of these exoplanets at present. This is where JWST comes in.
Thanks to its exquisite set of four instruments and high-resolution capability, JWST will be observing all 7 exoplanets in the Trappist-1 system using infrared imaging techniques and, most importantly, perform what we call transit spectroscopy.
Here’s a bit of background information to better understand transit spectroscopy. Instead of taking a snapshot of an object similar to the camera on your smartphone, spectroscopy uses a prism to break down light into its multiple colours (wavelengths), allowing us to characterise the object and better understand what it is made of (i.e.: elements, molecules). Spectroscopy is a powerful tool in space science and has been used for over six decades to study celestial objects of all types from stars, planets and moons to dust clouds and galaxies.
Transit spectroscopy is a technique that studies an object as it passes in front of its parent star (or any bright source) and measures the effect this transit will have on the incoming light (the spectra). This can tell us a lot about the object. Now, here is where things get really exciting; if a planetary object has an atmosphere, and our instruments are precise enough, we will be able to characterise the atmosphere’s composition as it filters the starlight that passes through it during transit. This is called atmospheric spectroscopy and has been used for over two decades now to identify what exoplanet atmospheres are made of (amongst other things).
If the Trappist-1 exoplanets have atmospheres, which is currently not known, JWST will be observing them during multiple transits (as well as eclipses) and measure their compositions with enough accuracy to identify biomarkers - gasp. These are atmospheric gazes that exist in concentrations high enough that abiotic origin is unlikely such as on Earth. Biomarkers include oxygen, methane, and ozone, to name a few.
In other words, JWST will show us in the coming months if there is life - as we know it - on one of the seven terrestrial exoplanets of the Trappist-1 system! I’m not sure about you, but I’ve never felt we’ve been so close to answering one of the most important questions in science: is there life out there?
Table showing the transit spectroscopies that will be performed by JWST during Cycle 1