Astrophysics: “We’re hunting exoplanets to look for life far away”

Look for signs of life or the conditions under which it can form or be hosted far away from Earth. The study of exoplanets, worlds that orbit stars other than our Sun, is truly experiencing a period of great effervescence.

“Their discovery – explains Giuseppina Micela, a researcher at the National Institute of Astrophysics – was a turning point in our understanding of the universe, both from a scientific and a philosophical point of view. We can now understand how “ordinary” our solar system is in space and how planets form, as well as what the conditions might be that favor the birth of extraterrestrial life. In addition, the search for exoplanets enables the development of advanced technologies such as space and ground-based telescopes and new methodologies for detection and data analysis.” It is no coincidence that to identify these exoplanets – adds Inaf Catania director Isabella Pagano – “various techniques have been developed. The most profitable so far was “transit” which consists in measuring the periodic changes in the star’s brightness due to the darkening of part of the star’s surface when the planet orbiting the star is along the line of sight of the observer on Earth. During the transition, the star’s brightness decreases slightly. By analyzing how much and how much starlight is lost during transit and by studying the periodicity of the phenomenon, it is possible to infer various characteristics of the planet, such as its size and the parameters of its orbit.” Another widely used method for searching for exoplanets is to measure the very small velocity fluctuations that a star due to its orbit around the center of gravity of the system, it exhibits the Doppler phenomenon. Mass and size values ​​for the identified exoplanet are then indirectly calculated, while also understanding its nature, such as whether it is rocky or gaseous. There are still other research methods: the gravitational microlensing effect, which allows the discovery of exoplanets very far from us, and the search for “variations in the arrival times of signals”, which allows the discovery of gravitational effects produced by bodies of planetary mass. . Psr B1257+12b, a body with a mass of 2 hundredths of the mass of the Earth, orbiting a pulsar, i.e. a highly magnetized and rapidly rotating neutron star, generated by the remnants of an explosion, was discovered by this method in 1992. supernovae.

But what are the most important exoplanets discovered so far? The list is constantly updated «but – continues Micela – if I had to list some of them, I would certainly include 51 Peg b, the first exoplanet orbiting a star similar to the Sun, which won its discoverers a Nobel Prize. This planet, in addition to opening a new field of research, belongs to the class of “hot Jupiters”, that is, planets with dimensions and mass similar to Jupiter, but very close to the parent star, with temperatures close to 1000 degrees. Theories of planet formation did not predict the birth of planets in such hot zones, so their discovery challenged models of the mechanisms of formation of planetary systems. Another important planet, if only for its proximity to us, is Proxima Centauri b, which orbits the nearest star of the solar system. The planet is located in the so-called habitable zone, with physical conditions compatible with the presence of liquid water, a component considered essential for the origin of life. Finally, a system that is also very interesting is the system around V1298 Tau with 4 known planets, it is a young star that is very similar to what the Sun must have looked like shortly after its formation. This system is important for studying the history of our system.”

And Italy plays an important role in the great risk of research. «The Italian astrophysics and planetology community has a good international standing and has access to relevant observational and computational resources – says Pagano –. We participate in the definition, construction and use of ESO (European Southern Observatory) instruments, where we already have telescopes suitable for the research and characterization of exoplanets and we are waiting for a new class of ELT instruments, the European Large Telescope, which with its almost 40 m in diameter will expand the boundaries in the coming years knowledge in this industry. We are involved in the Cheops, Plato and Ariel missions of the European Space Agency (ESA). We then have the opportunity to use much of the observing time available with Harps-N on the Telescopio Nazionale Galileo (Tng), a very high spectral resolution spectrograph with which we measure the planetary masses and atmospheric properties of the largest planets closest to their star. Finally, Shark-Nir and Shark-Vis were designed and built with Italian guidance, two imaging cameras, one infrared and one for visible light, recently in operation at the Large Binocular Telescope in Arizona; with them we will be able to photograph massive planets far from their star, especially in recently formed systems, and study the regions of planet formation.”

What information do exoplanets give us about extraterrestrial life? He replies Micela: “We are still far from finding life on extrasolar planets, but we are taking very important steps in this direction to find out which planets have the right conditions for life to develop”. For example, it is first important to identify the planets that are located in the so-called “habitable zone” of the star. This is the region in which the atmospheric chemical-physical conditions could allow the presence of liquid water on the surface, a basic requirement for life as we know it. Finally, exoplanets could also have exomoons, which Pagano concludes are “difficult to detect” but which could provide additional clues to planet formation mechanisms.

Leave a Comment