Giovanni Covone, professor of astronomy and astrophysics and Luca Cacciapuoti, master's degree student in Physics, took part in the first discovery of an extrasolar terrestrial planet in the so-called habitable zone, of the Transiting Exoplanet Survey Satellite (TESS) space telescope NASA.
Designed and launched into orbit in order to find Earth-like planets in orbit around nearby stars, TESS discovered a planet part of a triple planetary system and among a few terrestrial planets identified so far in the habitable zone (i.e. the region around a star where the presence of liquid water on the surface of a planet is possible), around the TOI 700 star, from which it takes its name.
The team, led by Emily Gilbert (University of Chicago), presented the discovery of the planet named TOI 700 d during the American Astronomical Society annual conference in Honolulu.
“The discovery of the planet TOI 700 d is a fundamental scientific result for TESS,” says Giovanni Covone, an astrophysicist at the Physics Department of Federico II. "The planets so far discovered by TESS were either out of the habitable zone or of much greater mass than Earth, gas systems more similar to Neptune than to Earth."
TESS reveals the presence of a planet around a star by observing the periodic decrease in brightness of the star caused by the planet as it passes in front of it.
“The TOI 700 planetary system is relatively close to us, about 101 light years away. The star is a small red dwarf, smaller and less luminous than the Sun: its mass is about 40% of the solar one. The fact that it is a quiet star, almost as much as the Sun, with minimal variations in brightness makes the newly discovered planet more interesting for studies on its possible habitability, "underlines Professor Covone.
The discovered planetary system is a triple system. The innermost planet, TOI 700 b, is almost exactly the size of Earth, is likely rocky, and completes one orbit every 10 days. The average planet, TOI 700 c, is 2,6 times larger than Earth - between the sizes of Earth and Neptune - it orbits every 16 days and is probably a gaseous world. TOI 700 d, the outermost planet and the only one in the habitable zone, has a radius of 20% larger than the Earth and turns around its star in just 37 days.
To date, the exact physical conditions on the surface of the TOI 700 d are unknown. Scientists used the information available to generate climate models of the planet on the computer and compare with the conditions of our planet.
"In the coming years we will be able to obtain spectroscopic observations of these planets and confirm or deny these models," concludes Giovanni Covone. "It will be an even more exciting moment because we don't know what to expect when we have new data from these alien worlds."