One thing you don't know about the Webb Telescope
And an invitation to LUVOIR . The search for life must come first!
I have been involved in astronomy for more than 30 years, and since the beginning of my career,
I have always wondered why in life I embraced this profession
at the expense of other youthful passions. This question has always remained unanswered.
As much as I tried to explain the choice with a certain propensity for mathematics,
I felt that the problem remained at a deeper and more elusive level.
Until one night, outside the Astrophysical Station in Bosque Alegre, Argentina,
smoking a cigarette under an oppressively beautiful southern sky, I wondered: "If all
I am seeing now was just a collection of gas and inanimate matter, if there was no hope of finding
a single paramecium in the entire universe... would I still have the enthusiasm to continue?
Would I feel the same things I feel right now? If we really were alone, in the entire universe.
If after centuries of searches, explorations, of long and disappointing listening... only the
echo coming back from the walls of an empty room would sadly reach us from the probes:
would we still be here? At our instruments, I mean, sacrificially
pursuing distant and unconscious objects?" Well, that night I finally understood that
for me astronomy, space exploration, and everything I had followed with passion until then,
were just a means to get to the only thing that can give meaning to existence:
the search for extraterrestrial life. Some of my colleagues think that my
attitude is rather childish, but it leaves me completely indifferent.
What is important to me at this moment is to explain why I am telling you these things...
It is not a desire to be a protagonist, but only the desire to communicate my point of
view on the Webb telescope... that despite what you read around is not,
in my opinion, the right instrument for the study of extrasolar planets.
And also on the LUVOIR Telescope, an opportunity that should not be wasted!
Want to know more? Then follow me!
As I told you, I am so convinced that the current purpose of astronomy should be the search for
life - even before astrophysical research - that I feel compelled to go against the grain
on what we can expect from the Webb telescope. I am obviously happy for the success of the
launch and for the good progress of all subsequent operations, but I am not very
optimistic about its ability to give us answers about the habitability of extrasolar planets
Ok, no doubt... assuming that its complex, month-long deployment in space works as planned,
Webb will become the most powerful and far-seeing observatory in the sky.
It will have unprecedented capabilities to probe the earliest days of the universe, shedding new
light on the formation of the first stars and galaxies. And it will observe in new detail the
most distant regions of our solar system. Deep space astrophysics is what Webb was
designed for in the early '90s and this will be his real specialty: to investigate the matter,
to go back to the origin of the universe, to explain black holes and dark matter...
but we should not hide the fact that in those years exoplanets had not been discovered yet,
and therefore the instrumentation on board for that kind of research was only adapted afterward.
Then there is the question of priorities ... Not only 90% of Webb's observing time
will be devoted to solving problems of strict astrophysical observance,
but there will also be a distinction for the remaining 10% dedicated to extrasolar planets.
On balance, reviewing the proposals already filed by hundreds of astronomers, more than 9% of these
concern the physics of exoplanets, not their biochemistry. Many of the first observations
of the telescope - to say - will concern the so-called "Hot Jupiters", gas giants in which
the presence of life can be excluded a priori). Only 1% telescope-time will be available to those
who want to try to capture the presence of biological signatures in Earth-like planets.
And I still do not know if this ostentatious lack of interest in the "search for life first" is due
to the awareness of the astronomical community of Webb's reduced capabilities in this sense,
or to the fear that the interest in this topic could be judged sentimental by other colleagues...
One must then consider that the method that Webb will use to examine planetary atmospheres,
is that of "transit spectroscopy". This implies waiting for the transit of a planet on the disk
of its star in order to identify - backlit by the background light - the atmospheric
corona that surrounds it,. It is hoped that through spectroscopy we can then determine the
composition by examining the spectral lines. However, this is not true for all planets.
Apart from the obvious exclusion of those that never transit the disk, it must be said that for
its design, Webb has limitations and can successfully study only certain types of objects:
mostly, exoplanets orbiting M-type stars, or red dwarfs. No terrestrial
planets around stars similar to our Sun, then! Red dwarfs are small-mass, low-luminosity stars,
and are by far the most common type of stars in the galaxy, but they are also stars
subject to fierce bursts of radiation that could sterilize the surface of their eventual planets.
As an aside, I'm afraid the signals we'll get from rocky planets around red dwarfs will be
very, very faint. They might be enough to tell us that an atmosphere is present, but
the odds of them telling us anything about their biological signatures are very, very slim indeed.
"Hey, guys, just a moment before we continue... BE sure to join the Insane Curiosity Channel...
Click on the bell, you will help us to make products of ever-higher quality!"
To make matters worse, Webb may have further difficulty detecting even the main sign of
life that an exoplanet's atmosphere can offer us: oxygen! For two good reasons.
The first is that Webb can only detect light emitted in the infrared part of
the electromagnetic spectrum, while oxygen is most detectable in visible light emissions.
The second is that a team of researchers recently discovered that even the atmosphere of a planet
with an extremely small amount of oxygen could still be able to support life.
And that precisely because of this characteristic Webb would judge sterile.
All this may be disappointing for many of you, but if you do not want to believe me,
at least pay attention to the opinion of some of my colleagues ... I am certainly not the only one
to be so skeptical about the possibilities of Webb in the role of "life seeker"!
Harold Connolly, who is currently involved with two asteroid sample return missions - OSIRIS-Rex
and Hayabusa2 - recently said: "In my thinking, we will never be able to prove
definitively through the data collected by Webb that a specific planetary body contains life.
Habitable, most likely yes, or at least by our current definition of what life needs to survive,
but life for certain, I don't think so." Ernst de Mooij and Chris Watson, both researchers
from Queen's University Belfast in the U.K., have instead declared: "The search for potential
biosignatures is fraught with challenges. Not only will any signals be small and difficult to detect,
but there are also significant possibilities of finding false positives, where signals are
falsely attributed to biological origins, as well as false negatives - where genuine
signals may be attributed to other causes." Laura Kreidberg, who is director of the
Atmospheric Physics of Exoplanets Department at the Max Planck Institute, said Webb will not be
able to "definitively" identify biosignatures." And when asked, "Will Webb be able to identify
life on other planets?", Shawn Domagal-Goldman, an astrobiologist at NASA's Goddard Space Flight
Center, said, "I think the answer is, 'We shouldn't count on it. '"
To summarize... Webb is a wonderful instrument, that in the astrophysical field will
certainly revolutionize our current vision of the universe, but unfortunately will
not be able to meet the expectations of those who, like me, and like many of you,
put the search for life before everything else. However, it seems, our position is not at all
eccentric and minority in astronomy ... A few weeks ago, in fact, the National Academy of
Sciences, in its Decadal Survey on Astronomy and Astrophysics, has expressed in this way:
"NASA should begin developing a space mission that can tell us whether life on nearby planets
is abundant, rare, or essentially absent!" The Decadal Survey is a document by the
science community, an assessment of where we are scientifically in astronomy and
astrophysics currently and where we want to progress in the next decade. It’s a
stop at the map in the astronomy food court, charting a path to the next stop.
The 2000 Decadal Survey recommended what would become the Webb telescope. The 2010 survey
recommended the Nancy Grace Roman telescope, scheduled to launch no later than May 2027.
The 2020 Decadal Survey, delayed by one year because of Covid-19,
has directed its specific recommendations towards the construction of a space telescope
capable of giving a definitive answer to the long-standing question of life in space.
A telescope that at least in its general lines has already been conceived and also has a name:
LUVOIR, an acronym for Large Ultraviolet Optical Infrared Surveyor.
The only problem is that the LUVOIR Study Team has produced designs for two variants: one with
a 15.1 m diameter telescope mirror (LUVOIR-A) and one with an 8 m diameter mirror (LUVOIR-B).
Both versions are intended to be serviceable and to operate at the Sun-Earth L2 Lagrangian point
(about 1.5 million kilometers from Earth), where LUVOIR, like Webb,
may maintain a stable orbit in the long term.
LUVOIR’s strength - and weakness - has the enormity of its segmented mirror. This mirror
would allow astronomers to discover and study hundreds of exoplanets while also performing
revolutionary observations across a wide swath of general astrophysics.
Assuming any true-blue Earth-like worlds exist around the sun’s neighboring stars,
LUVOIR should offer the best odds of finding them. But putting such a demanding deployable
mirror into space translates to an astronomical cost. Estimates at NASA’s Goddard Space Flight
Center have arrived in the realm of $20 billion for LUVOIR-A and $15 billion for LUVOIR-B.
For the timing of realization, we speak of about 20 years from now, with the launch
that could take place in the early forties. Well, I’m also here to tell you this... for
my part, I strongly and absolutely support the 15-meter version!
And I would ask you to support my position... So, talk about it with your friends,
write about it on your social networks, do as you please... The important thing is that when
the United States Congress has to decide which instrument to finance, its choice falls on the
15-meter version! It would be a huge mistake if, in order to save a few billion dollars (the
cost of a few stealth bombers), Congress would fall back on the smaller and cheaper version!
Of course, the 8 meters of LUVOIR-B are already something more than the 6.5 meters of the Webb
telescope, but the analysis of the increase in diameter of telescopes over time shows that when
you pass from one technological generation to another, the increase must be at least double.
With Luvoir-A we will really have the opportunity to remove from our minds the eternal question,
the one that has always nagged us. Why waste this opportunity?
Not to mention that under the emotional thrust of this grandiose undertaking,
the instrument could be ready in less than half of the 20 years foreseen,
taking advantage of the experience accumulated with the design and construction of Webb.
If we want definitive answers to the biggest questions of all,
it takes a big effort and a substantial investment. Considering that the reward
is learning that “there’s life on that planet, orbiting another star,
right over there,” it’s clear that LUVOIR-A is the one telescope we must all join together to build.