Nature sets a lower limit on stellar masses: objects less massive than 0.07-0.08 solar masses are incapable of initiating the thermonuclear reactions that power more massive stars. Below this threshold lies the realm of brown dwarfs, objects whose mass is too small to qualify as stars, yet too large to be categorized as planets. The mechanism responsible for the
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Several questions about the star formation process are still debated. For instance, we know that stars form from the gravitational contraction of clouds of gas and dust, called “molecular clouds,” since they are mainly made of molecular hydrogen. Mainly thanks to observations from the Herschel satellite, we also know that most star formation occurs in long filaments embedded in these
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The Vera C. Rubin is currently under construction in Cerro Pachón, northern Chile. Equipped with an 8.4-meter primary mirror, the telescope is designed to monitor the entire visible sky for ten years with six filters that cover the entire optical band, along with part of the UV band (the u filter) and the IR band (the y filter). This survey, known
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Without any doubts, the supernova remnants SN1987A is the one that taught us more about this class of objects and supernova exposions. Produced by a supernova exploded in the Large Magellanic Cloud on February 23rd 1987, this is the only case in which we have observations of the progenitor, of the supernova explosion, and in which we follow the development
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Flares are among the most energetic magnetic phenomena occuring in stars. They are triggered by a sudden release of energy previously stored in the stellar magnetic field, and then they culminate with the formation of magnetic loops in the stellar coronae filled by X-ray and UV emitting plasma at million degrees. Sometimes, these magnetic structures erupt, releasing in the surrounding
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Supernova remnants (expanding clouds produced by the explosion of massive stars) are fascinating objects. Their study, in fact, can unveil the physical processes working during supernova explosions and even the properties of the stellar progenitors. To these aims, of particular importance is the analysis of the physical and chemical properties of the ejecta (which are the fragments of the dying
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Almost all stars in the Universe produce their own magnetic field with a process called stellar dynamo, whose basic ingredients are stellar rotation and convection. In general, magnetic fields are produced and are affected by charged particles, which is what stellar plasma is made of. In stars the magnetic field and plasma thus interact, producing a class of transient phenomena
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X-ray astronomy explores the high-energy Universe. X-rays are, in fact, high energy photons emitted by very hot gas (with temperature of some milion degrees) or by processes involving relativistic particles. Some astronomical sources of X-rays radiation are: accreting black holes, such as the supermassive black holes at the center of active galaxies, stellar coronae, supernova remnants, and clusters of galaxies.
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Our planet is constantly bombarded by energetic particles (mainly protons) called “cosmic rays“. The study of cosmic rays is a leading science topic given its importance in several fields, such as the study of the effects on instrumentation and astronauts in space, where the natural protection against these particles provided by the magnetic field of Earth is low or null.
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