I brillamenti stellari possono contaminare le osservazioni realizzate durante i transiti degli esopianeti I brillamenti sono i fenomeni stellari di origine magnetica più spettacolari. Si innescano a seguito di improvvisi rilasci di energia da parte del campo magnetico che riscaldano il plasma stellare fino a milioni di gradi, creando enormi strutture ed emettendo radiazione in praticamente tutte le bande
» Read more
Connessioni magnetiche tra stella e pianeti nel sistema esoplanetario più vicino a noi La maggior parte delle stelle produce un campo magnetico al proprio interno che, interagendo con il plasma stellare, genera tutta una classe di fenomeni ad alta e altissima energia di grande interesse scientifico. Un esempio tipico sono i brillamenti (flares): improvvisi rilasci di energia in strutture
» Read more
The solar corona is a structure that extends for several solar radii and is filled with low-density plasma at temperatures of millions of degrees. What heats coronal plasma to such extreme temperatures? It appears to be a combination of complex magnetic phenomena. X-ray and UV observations of the Sun reveal an atmosphere rich in bright structures that host million-degree
» Read more
Despite the wide array of telescopes and satellites available to the astronomical community, there is a type of radiation to which we are virtually blind: the extreme UV band. This is high-energy radiation with a wavelength that ranges from the Lyman-α emission, caused by hydrogen atoms whose electron transitions from the innermost orbital (the ground state) to the second (n=2),
» Read more
The corona is the outermost part of the Solar atmosphere, filled with plasma at temperatures reaching several million degrees. The mechanism responsible for heating the Solar plasma to these temperatures is a long-standing problem. It began in the 1930s when physicists Bengt Edlen and Walter Grotrian proposed that the mysterious spectroscopic lines observed in the corona were not due to
» Read more
Flares are transient and energetic phenomena that occur in most stars and can be observed with high spatial and temporal resolution in the Sun. These phenomena are triggered by a sudden release of energy previously stored in the star’s magnetic field, which, after a sequence of events, leads to extreme heating of the stellar plasma. The heated plasma then rapidly
» Read more
Stars are variable sources over timescales which depend on the phenomena triggering this variability. These phenomena are typically produced by the interaction between the stellar magnetic field and its plasma. Typical examples, observed and studied in great details in the Sun, are: flares (sudden release of a large amount of energy by the magnetic field which heats the gas in
» Read more
The corona is the outermost part of the atmosphere in stars with intermediate and low mass. In this region, which is extended for several stellar radii, the plasma can reach temperatures of several million degrees, emitting mainly X-ray radiation. The coronal temperature varies over a range of several orders of magnitude as a function of several stellar parameters, such as
» Read more
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
» Read more
Solar corona is made of plasma at million degrees. The mechanism responsible for the heating of the corona, which is the outer part of the solar atmosphere, is still one of the unsolved problems of solar physics. For comparison, the plasma in the photosphere is on average at about 5600 degrees. It is widely accepted that the responsible for heating
» Read more