A “transit” occurs when we observe a planet moving across the disc of its star. Thus, during the transit the planet obscures a small portion of its star, slightly reducing its luminosity. While in the Solar System the only planets we can observe transiting in front of the Sun are Mercury and Venus, transits is still the most efficient method
Ultra-hot Jupiters are gaseous planets orbiting at close distances from their central stars, with rotation periods shorter than 3 days. Their atmospheres are thus heated, more than 2000 degrees, by the incident radiation emitted by the central star. For this reason, the atmospheres of ultra-hot Jupiters shows peculiar properties compared with planets of other types. For instance, they are affected
The study of protoplanetary disks (which are disks orbiting around young pre-main sequence stars) is of great interest since planets formation occurs in these structures. Disks are dispersed in a few million years (typically less than 10 Myrs) by the planets formation itself, the accretion of material onto the central star, and the loss of material launched in a highly
The mechanisms involved in the formation of planets are still not completely understood. The most widely accepted model that describe the formation of gaseous planets is the core-accretion model. In this paradigm, the formation of these planets starts with the formation of a large rocky core by the coagulation of planetesimals, followed by the accretion of a large gaseous envelope
Determining stellar ages can be a difficult task. One of the main difficulties is due to the fact that methods to evaluate stellar ages are specialized for given types of stars and they do not work for the others. Besides, during the longest phase in stellar evolution, the Main Sequence, stellar parameters such as radius and temperature do not change
Some of the exoplanets known so far belong to classes that do not exist in our Solar System. For instance, the class of the Hot Jupiters, i.e., gaseous giant planets orbiting at close distances from their stars (typically less than 0.5 AU, Astronomical Unit, where a 1 AU is the average distance between Sun and Earth, about 150 million km).
Supernova explosions, occurring and the end of the life of massive stars, are ruled by a complex physics, and they can not be described by a simple spherically symmetric geometry. The rarity of these events make even more difficult to understand the physical processes involved during the explosions. For instance, on average only one supernova explodes in our Galaxy every
Stars which are not fully radiative (e.g., less massive than 8 solar masses) produce a magnetic field in their interior whose intensity and topology depends on the type of star and internal structure. The magnetic field is then drag toward the surface and here it interacts with the plasma in the photosphere, chromosphere, and corona triggering phenomena classified as “magnetic
Despite theoretical models predict a large abundance of Earth-like planets in our Galaxy, the family of the 4284 planets discovered so far (updated at 2020/9/25, credits: NASA) counts relatively a few of such a planets. This is clearly an observational bias, due to the fact that the methods used to detect planets are not sensitive to small planets. For this
