A cura di Giorgio Buttarelli-
NASA astronomers have discovered seven Earth-sized planets orbiting a star 40 light years distant from our solar system. Three of these worlds fall within the so-called “habitable zone” where temperatures are rather mild and liquid water is more likely to form. The system is named after “The Transiting Planets and Planetesimals Small Telescope” in Chile, which led to the discovery of three of these planets back in May 2016. Later on, the Spitzer Space Telescope confirmed the existence of these planets and revealed others. These results were published on February 22 in the journal “Nature” and were announced during a news conference at NASA Headquarters in Washington.
Since the search for an “Earth-two” has begun, thousands of Exoplanets have been discovered but only a small number of them meet the criteria for being possible new Earths. The planets in the TRAPPIST-1 system are fairly close to each other and the view from one of them would reveal the others to look even bigger than we see the Moon in our skies. The worlds are set on very tight orbits and it takes them between 1.5 and 20 days to revolve around the star. At such proximity, it is likely that most of them will be “tidally locked”, which means that they show only one face to TRAPPIST-1 star, just as the Moon does with Earth. All of these seven planets are allegedly rocky and could host liquid water under the right atmospheric conditions, but the chances are higher with the three in the habitable zone (TRAPPIST-1 e, f, and g). Two of these planets located in the habitable zone are about the same size as the Earth and they even receive around the same amount of light as Earth does from its sun. NASA’s upcoming James Webb Space Telescope, launching in 2018, will be able to detect traces of water, methane, oxygen, ozone, and other components of a planet’s atmosphere. Webb will also analyze planets’ temperatures and surface pressures, which are regarded as key factors in assessing their habitability. TRAPPIST-1 star is classified as an ultra-cool dwarf star, which is slightly bigger than Jupiter and shines a light 2000 times weaker than our sun’s. Its solar activity could have been stronger in the past and therefore could have affected the nearby worlds.
We have never been closer to answering the question “are we truly are alone out there”. The existence of life beyond our solar system could challenge our own sense of priority in the Universe. I do not know if anyone would ever respond to our call in the dark but I do believe that the Universe made us its special interlocutors. It reminds us every day through the beauty of life that we do belong here, as a privileged part of it. Like sailors clinging to their rocky vessel, we have home in this silent ocean and we venture through its tides pushed by faith.