James Webb Telescope’s Discovery of Life on Trappist-1 Planets Will Change Everything
Believe it or not, we are in the era of exoplanets.
Since the first exoplanet was discovered, in 1992, astronomers have been looking for them,
hunting them, because they could be hiding the biggest treasure of all: life.
Both space telescopes and ground telescopes are needed to study the
atmospheres of such far extraterrestrial worlds. The JWST is the perfect candidate
to finally give us the answer to the question: are we alone in the universe?
I'm talking seriously! One of NASA's telescopes is to revolutionize our understanding of exoplanets.
The plan is quite clear: during its first year,
it will spend a significant amount of time studying potentially habitable star systems.
To be more precise, JWST will spend a full quarter of its time around the Lagrangian point
L2 studying exoplanets. But perhaps the most interesting part is that almost ten percent of
these exoplanet observations will be used to stare at the distant and mysterious star TRAPPIST-1.
TRAPPIST-1 is known to have planets orbiting around it.
What can this tiny planetary system teach us about life as we know it and planetary evolution?
Let's find out!
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So the news is: the James Webb Space Telescope has started peering at the most tantalizing candidates
for life elsewhere in the universe—a group of exoplanets in the star system known as TRAPPIST-1.
Astronomers are happy. You may ask why, and this is the answer:
first of all, having a telescope like Webb observing a planetary system is exciting on
its own. But what is even more exciting is the wealth of data JWST will send back to Earth.
It will be huge, and it will be precious.
Astronomers from all over the world can't wait to have those data in their hands, and
to analyze them, possibly providing new insights into planetary formation and life as we know it.
Basically, in the coming years, we will have a completely new understanding of the star systems.
This would be crucial to constrain the presence of life in the universe.
TRAPPIST-1 is a small red star, an ultracool M-type dwarf. It belongs to the smallest class
of stars. TRAPPIST-1 didnì't like to be alone. The circumstellar disk collapsed through gravity,
and planets started to form. We know this because we can actually infer
the presence of these planets, even though we've never directly seen them.
What astronomers noticed while studying the system in 2016 and 2017 was that, from time to time,
the star would become dimmer. This actually happened at precise times, and they understood
this dim light was given by exoplanets crossing the stellar disk of TRAPPIST-1, every period.
The method used to find these planets is called the transit method,
and it is vastly used in astronomy. As of today, we know about seven rocky
planets — TRAPPIST-1b, c, d, e, f, g, and h — closely orbiting their diminutive host star.
This is an artist's representation of the Trappist-1 system with the exoplanets at
scale between each other and the host red dwarf star. Every planet is associated with
an Earth similarity index, ESI. It tells us how similar a planet is to Earth. For example,
the ESI for Venus is 0.44, for Mars is 0.64 and for the Earth, itself is, of course, 1.
But be careful: the ESI is not a direct measure of habitability of a planet,
but formally a fuzzy comparison, using a distance metric,
between a selected set of planetary properties of a planet and Earth.
However, what makes Trappist so interesting is not the number of present exoplanets,
but rather some of their qualities.
All seven TRAPPIST planets orbit their host very closely. Even the most distant — TRAPPIST-1h —
orbits at only 0.062 astronomical units (AU), six times closer than Mercury is to the Sun.
Now, let's be honest: if we were this close to the Sun, we would be long gone. But TRAPPIST-1 is way
cooler than our Sun. So there's basically no problem. Temperatures could be fine.
TRAPPIST-1’s radius is only 12% that of the Sun, so it's just a little
bigger than Jupiter, and this was also a plus because, for a given planet radius,
the transit signal is easier to detect for a smaller star.
But now let's get to the main question: what's Webb supposed to do?
It will give us insights into TRAPPIST-1's planetary atmospheres.
The technical name for it is “atmospheric reconnaissance” — testing whether an
atmosphere even exists around the TRAPPIST-1 planets. In fact, astronomers know very well
that having an atmosphere is a fundamental prerequisite for life as we know it. Moreover,
the study of an atmosphere can tell us whether biosignatures are present or not.
A biosignature is the observational marker of organic molecules: they're associated with life.
Some examples of biosignatures are minerals, or maybe biologically
formed cement, microfossils, and films. Determining if a potential biosignature
is worth being investigated is a fundamentally complicated process. Scientists must consider any
and every possible alternative explanation before concluding that something is a true biosignature.
This includes investigating the minute details that make other planets unique and being able to
understand when there is a deviation from the expected non-biological processes present on
a planet. In the case of a planet with life, it is possible that these differences can be
extremely small or not present at all, adding to the difficulties of discovering a biosignature.
Years of scientific studies have culminated in three criteria that
a potential biosignature must meet in order to be considered viable for further research:
Reliability, survivability, and detectability.
Needless to say, this will not be the first time scientists will look for biosignatures.
Since TRAPPIST-1's discovery in 2017,
scientists have used Hubble to attempt to detect atmospheres around the seven planets.
What they found is that the small planets did not have a large, puffy atmosphere, for sure.
But they were unable to convincingly detect smaller, thinner atmospheres, like our own.
Now, we all know that HST time is coming to an end, and JWST is a more powerful instrument.
Indeed, it will be able to detect details and subtleties that Hubble can't.
The first difference is that Webb has a much larger mirror than Hubble,
and its collecting area is about six times HST's mirror area.
The second thing is that JWST operates in the mid-infrared regime,
where cool stars emit most of their light. For these reasons, Webb is the perfect instrument
to study TRAPPIST-1 in detail and maybe unveil the mystery of life as we know it.
In JWST’s first year, astronomers will check each
planet in the TRAPPIST-1 system for signs of an atmosphere.
Hopefully, they will find something exciting. Make sure to be ready when the revolution comes!
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Detecting atmospheres around the TRAPPIST-1 planets would have
major implications for the study of exoplanets.
For instance, it is widely believed among the scientific community that
if a planet is this close to its host star,
solar flares from the star might destroy and completely remove its atmosphere.
Moreover, being this close to the star, the tidal forces acting on these planets could
be so strong that the properties of their atmospheres might be dramatically altered.
The method scientists will use to work out whether or not the
TRAPPIST-1 planets have atmospheres is called transit spectroscopy.
Spectroscopy is the process of collecting light from an object and splitting it into
its components by means of a disperser, thus giving the so-called spectrum.
In the case of transit spectroscopy, it consists of taking a spectrum when the planet is transiting
the star's disk. If that sunlight passed through a planet's atmosphere on its way to Earth,
then there will be telltale signs in the spectrum of that light. In this way, one
can have imprints of the chemical signature of the atmosphere that appear in the spectroscopic data.
Until now, it seems that, because TRAPPIST-1 is so cool, liquid water can condense on planets d,
e, f, and g. According to some studies, these planets would orbit in the so-called
habitable zone, and they could be home to vast oceans on their surfaces.
But habitability doesn't only depend on the temperature of the star. It
depends on the star's winds and activity, the presence of moons,
and the orientation of the axial tilt of the planets themselves. Apparently, all these factors,
along with the planet's rotation rate, could be key factors for habitability.
Some recent studies confirmed that Trappist-1 is the one most likely to be habitable. Analyzing
various scenarios based on different climate models, the authors believe that only planets d
and e are able to develop vegetation somewhere on their surface, suggesting that the outer planets,
f, g, and h are too cold, while b and c would be too hot to keep water in a liquid state.
The planet e would have large surface areas where vegetation could grow,
and this would further mitigate the global average temperature of the planet,
making it habitable even on 100% of its surface. Planet d, on the other hand,
would have only a limited area along the terminators where vegetation could develop,
and the maximum temperatures (of the daytime side) and minimum temperatures
(of the hemisphere always in the dark) would be much more extreme than on Trappist-1
Anyway, when we talk about other star systems,
we should always keep in mind they are very different from our Solar system.
TRAPPIST-1 is so different from the Sun, and the planets orbit so close to it,
that it’s likely that there will be many surprises. And we can't wait to find out more!
But what do scientists really think about JWST and the discovery of life?
They said they're cautiously optimistic, but the public shouldn’t expect any announcements
of biosignature detection in the first year, because detecting biosignatures is the long game.
And let's suppose JWST doesn't find anything. No forms of life, no atmospheres on these planets.
Should we be disappointed? Well, of course not! Just because we were unlucky,
this doesn't mean our mission failed. Observations of TRAPPIST-1 will change history.
Studying terrestrial exoplanet atmospheres is a multi-step process,
with the eventual goal of detecting worlds like our own.
It will be another piece to add to the amazing puzzle of the universe.
This video ends here! What do you think about TRAPPIST-1? Let us know in the comments below! And
if you enjoyed the video, don't forget to share it, and I'll see you next time on the channel.