NASA has just certified the existence of the 5,000th exoplanet. Rita Sambruna of the Goddard Space Flight Center: «The search for an Earth 2.0 is the Holy Grail of astrophysics. Also to answer the fundamental question: are we alone in the Universe? “
Imagine planets orbiting their own sun. Planets where the conditions for organic life potentially exist, but outside the Solar System. And like the Earth they draw energy and light from their star. Now stop imagining why these planets exist: they are called “exoplanets” or exoplanets. And there are not a few. The American space agency, NASA, has just certified the existence of the 5,000th exoplanet. There are similar to Saturn and Jupiter, the largest in the Solar System: gas giants that can reach temperatures higher than that of stars. Or like Neptune: giants of ice. But every twenty of these exoplanets we find one “terrestrial”, that is, made of rock. Finally, there are also super-Earths, with a dimension between our planet and Neptune.
Five thousand is just a number, one might think. Nothing different from 4,999 or 5,001. But in reality it is a number that matters a lot because, until a few years ago, we thought we were the only ones to have a solar system with an Earth and a few other planets that are part of it (we have always made the same mistake from the beginning).
A new world
The first exoplanet was only sighted in 1992, exactly 30 years ago. Alexander Wolszczan, the scientist who signed the article in which it was unveiled, predicted that “if we can find a planet around a neutron star, we can find them everywhere.” In fact, today NASA estimates that there are hundreds of billions of them in our galaxy alone, the Milky Way. “It’s not just a number – said Jessie Christiansen, scientist responsible for the archive and research of exoplanets with NASA for the Caltech Science Institute in Pasadena – each of these is a new world, a new planet. I am enthusiastic about each of them because we know nothing about them ». In the last cluster that allowed us to reach the 5,000 mark, we discovered 65, all together. More than one percent of the total. So the question is: what has changed since the 1990s? We have learned what to look for. «Exoplanets – explains Rita Sambruna, Deputy Director of the Division of Astrophysics of the Goddard Space Flight Center, the largest scientific center of NASA, in Greenbelt, Maryland – are hot territory for research in astrophysics. And the holy grail of this mapping is to find a planet similar to Earth and potentially habitable by organic life like ours, based on coal and water; one of the fundamental questions of NASA is “Are we alone in the Universe?”. And to answer the first step is to find a planet that has characteristics similar to the Earth ».
Does Earth 2.0 exist?
It is called Enrico Fermi’s dilemma: the Nobel Prize in physics was skeptical of the existence of other forms of intelligence in the Universe (we would have already discovered traces of them, was his argument). But when we talk about traces of life we don’t necessarily have to think about intelligent life forms. «We already know that Mars – underlines Sambruna – once housed water. Is there a planet outside the solar system that has characteristics like the Earth? Or at least like Mars? The problem with this question is that, unlike the planets in the solar system that are close together, exoplanets are distant and difficult to find. Not only that: they are also difficult to study. Using special techniques, such as the transit in front of the parent star, which causes a spot in the star’s brightness due to the small dimming, we have found 5,000, using the space telescopes Kepler and his successor Tess ”.
Advanced tools and study progress
“With these techniques we are able to determine the mass and size of the exoplanet
, the distance from the star. And this already allows us to obtain some information: based on the mass and size, for example, we understand if the planet is rocky, like the Earth; the distance from the parent star informs us whether water on the planet can exist in a liquid state. Small, rocky planets, at the “right” distance from the star, are the closest to Earth in the sense that there may be water. And where there is water there could be life. With the most advanced instruments, such as the James Webb Space Telescope (which in this period gave excellent results in the first tests to focus images) and the Roman, we will also be able to study the atmosphere of the exoplanet, looking for chemical elements and complex molecules that are one more step in finding Earth 2.0, the twin of the Earth ».
Already in 2015, NASA had found the Kepler 452-b, a rock planet, the size of the Earth and at the “right distance from its Sun”. As Sigmund Freud said, the first mistake we made as humanity was to think we were at the center of the Universe. Copernicus and NASA helped us understand this.
March 23, 2022 (change March 23, 2022 | 17:30)
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