Astronomer Franck Marchis, a member of the SETI Institute, is convinced that we will soon be able to “see” living exoplanets directly.
Already more than 4,000 planets have been discovered outside the solar system. The researchers suspect that they are billions, just in our galaxy and many could contain liquid water and be supportive of the development of life. Today we even talk about potentially livable exolunes.
But in spite of hard efforts, we have never been able to detect any presence or any messages emitted by extraterrestrials. Even the mysterious “Wow!” Would have an explanation without needing to resort to the aliens.
Yet our radio telescopes and space telescopes are becoming more efficient. The Kepler successor TESS satellite is already adding up the discoveries, and NASA and the European Space Agency are promising even more precise new aircraft. Since 1984, the search for alien messages has even a dedicated institute: the SETI. Franck Marchis, Franco-American astronomer and researcher member of SETI, would prefer to see these extraterrestrials directly than to listen to them.
Engaged in multiple projects, he is confident that we will soon be able to get a picture of a planet similar to Earth, from ” another blue dot ” In the universe. How far can we zoom in on these distant worlds? Do they have a real chance of being inhabited? And how to explain the silence of extraterrestrial civilizations if they exist? Before the festival Star’s Up, to be held in Meudon on June 28 and 29 and where the astronomer will intervene, we discussed exoplanets and extraterrestrial life with him.
Franck Marchis: This is a reference to the “pale blue dot “, the famous photo of Earth taken by Voyager 1 in 1990, 6.4 billion kilometers away. It’s an iconic photo, which made us change scale. Before, there was the photo of “Lever de Terre” taken from the lunar orbit in 1968, which made us aware of the fragility of our planet.
But for my generation (I defended my thesis in 2000), it is the image of 1990 that marks a break: the moment when we understand that man is exploring the solar system. That was the main motivation of my work, to build big telescopes to understand the solar system.
I would like to bequeath to the next generation a new image: to show it another blue point, that of a cousin of the Earth. This will have the same psychological impact on a new generation of researchers, they will have a map, a place to look, a motivation to build even larger telescopes to see the surface of these blue dots, see if it houses vegetation, animals, a civilization.
There are about 150 stars located between 5 and 10 parsec around us [a parsec is about 3.26 light-years, about 31 000 billion kilometers, or 206 000 billion times the distance Earth – Sun, nldr]. If we find blue dots in half of them, that means that life is potentially possible everywhere, it would reinitialize our existence, it would be an awareness that we are certainly not alone, nor the only form of intelligent life.
If, on the other hand, there is only one blue planet or none, it would be the realization that our planet is really special.
Today we have many clues in the direction of this second hypothesis. The solar system is very particular, with 4 telluric planets and two gaseous giants. This is unique and very useful: when a planetary system is created, there are many fragments, comets, asteroids and plenty of water that remain in orbit around the star.
One of the models to explain the massive presence of water and oceans on Earth suggests that after the formation of planets, their orbits have adjusted, evolved.
And Saturn would have entered at one point in resonance with Jupiter, destabilizing comets and asteroids. These would have fallen in number with their water, especially on Earth. This is the “big late bombardment”A theory that one tries to prove to explain the presence of the terrestrial oceans.
Another theory emphasizes the role of shield played by Jupiter and Saturn to protect us, after this period, from other meteorite bombardments. This is important because it requires enormous stability in terms of climate and environment to allow life to evolve.
If a meteorite like the one that struck the dinosaurs fell every 10,000 years, it would be the equivalent of a reset for evolution, a life like ours could never have emerged.
One last example: the moon allows tides, which allow water to dry and some sediment to accumulate, which would have played a crucial role in the formation of RNA. It seems that there are so many special conditions in the solar system that have allowed the emergence and development of life on Earth.
Yes, we discover an ever increasing number of exoplanets. The first was discovered in 1995 and we exceeded 4,000 last week [ June 13, ed ]. But we do not really “see” these planets, we see their shadow passing in front of their star or the variations of movement of these stars.
This only gives us some information, like their density. At SETI, we seek to see them more directly, it is one of the greatest challenges of modern astronomy because these planets are a billion times less bright than their star and are in addition just next to it. It’s like looking for a firefly circling a large lighthouse 400 km away.
NASA is trying to do that with its own concepts. We are working on Project Blue. It is a small telescope of 30 or 40 cm, equipped with an adaptive optics system. The goal is to send it into space in 2021 to constantly scan Alpha Centauri A and B, two stars very close to us and orbiting one around the other.
The problem is that Proxima has a habitable zone very close to the star, equivalent to the orbit of Mercury and even below which makes it very difficult to observe planets.
We have not yet spotted exoplanets around Alpha Centauri A and B but since Proxima has two terrestrial planets, it is suspected that Alpha Centauri A and B, nearby and larger, also have a good chance of ‘to have some. In addition, these two stars are solar type, unlike Proxima.
This is a very anthropocentric argument but we would be more likely to detect a life similar to ours, so easier to recognize.
In the coming years we could obtain the image of a terrestrial planet, a small blue dot, with the color, the spectrum, information on its atmosphere.
Imagine that we discover strange things, or evidence of the presence of life: it would undoubtedly be a huge motivation to quickly build interferometers several kilometers in diameter to see these planets in detail, we could even map them.
Source: Usbeketrica
