The architecture of planetary systems is result from both the planet formation process and a complex mechanism of radial migration of planets. This has occurred also in the Solar System, whose final architecture resulted from the migration of the gaseous giants. In particular, the theories describing the formation and migration of super-Earths and Neptunian planets predict different configurations of the
The number of known exoplanets discovered so far (4197 planets, updated at 2020/August/4th, from NASA) is large enough to allow us to study their global properties. One of these properties, still lacking a proper explanation, is the so-called “Neptunian desert”, e.g. the lack of intermediate planets with orbital periods shorter than 3 days. One of the hypotheses that can explain the Neptunian
Terrestrial planets are common in the Milky Way. It has been estimated, in fact, that at least 30% of stars in the Solar neighborhood host a terrestrial planet, and this fraction increases to 40% considering the habitable zone around all M stars (e.g. stars with effective temperature between 2400 and 3700 degrees) of the Galaxy. The habitable zone is defined
Several fields in modern astronomy rely on high-precision photometric data. This is true, in particular, for the search of exoplanets with the method of transits. This method consists in searching very small periodic dimming of stellar emission due to the transit of planets along the line of sight during their orbits. For instance, the transit due to a Hot Jupiter (a gaseous
The discovery of the first exoplanet in 1995 was a challenge to our knowledge of the architecture of planetary systems. The planet orbiting around the star 51 Peg, in fact, was different than the planets in our Solar System: it was a gaseous giant orbiting at only 0.05 Astronomical Units (A.U., where 1 A.U. is the average distance between Earth
Hot Jupiters are gaseous planets orbiting very close to their stars, typically closer than 0.1 Astronomical Units (the average distance between Earth and Sun), and with very short orbital periods of days or even hours. An extreme sub-class of these planets are the ultra-Hot Jupiters. These planets are tidally-locked to their stars (which means that they show always the same
The “Ultra-Short Period” (USP) exoplanets have very close orbits and orbital periods shorter than one day. These planets typically have a radius smaller than 2 Earth radii and a terrestrial composition, sometime with an excess of iron. Four hypotheses have been made to explain the formation and evolution of USP planets. The main hypothesis is that these planets originate
“Super-Earths” are rocky exoplanets with a mass between that of Earth and Uranus. Some of these planets may also have a close orbit around the parent star. For instance, the super-Earth 55 Cancri e has a mass of 8.6 Earth masses and it orbits at a distance of 0.016 AU (Astronomical Unit, which is the average distance between Earth and
The final architecture of a planetary system is the result of a complex interplay between several processes, such as the dispersion of the protoplanetary disk from which the planetary system formed, and the gravitational interaction between the newborn planets. Besides, these processes can be affected by the environment and by their central star. One of the most important process dictating
