Supernova remnants, i.e. the remnant of supernovae explosions, are among the most interesting astronomical objects. In fact, they are not only produced by one of the most violent phenomenon occurring in the Universe (the explosion of a supernova from the collapse of the core of a massive star, i.e. a “core-collapse supernova”, which emits the same energy of 1033 atomic
di Mario Giuseppe Guarcello ( segui mguarce) Le stelle giovani, dette di pre-sequenza principale perchè ancora in fase di contrazione gravitazionale e con un nucleo troppo freddo e poco denso per poter produrre energia tramite le reazioni termonucleari che invece avvengono nelle stelle di sequenza principale, sono oggetti caraterizzati da fenomeni interessanti. Ad esempio, alcune di esse presentano
In the field of exoplanetary science, it is particularly important the study of exoplanets orbiting in the habitable zone, e. g. at a distance from their stars which allows water to be in liquid state at the surface of rocky planets. In particular, several projects such as MEarth (Irwin et al. 2015), APACHE (Sozzetti et al. 2013), and TRAPPIST (Gillon
di Mario Giuseppe Guarcello ( segui mguarce) I resti di supernova, ossia uno dei due prodotti di un’esplosione di supernova assieme all’oggetto compatto formato dal nucleo della stella esplosa, sono ritenuti i principali responsabili della produzione di raggi cosmici, che vengono accelerati fino ad energie di 3×1015 eV. L’accelerazione di raggi cosmici caratterizza tutta l’evoluzione dei resti di supernova,
Despite the stars in our Galaxy typically formed in stellar clusters, only a small fraction of them today is observed associated with a cluster. This led to the conclusion that stellar clusters typically disperse in 10-100 million years. Two mechanisms are thought to be responsible for the dispersion of stellar clusters. According to the model of the “residual gas expulsion”,
di Mario Giuseppe Guarcello ( segui mguarce) È stato pubblicato sul sito del satellite Chandra della NASA un articolo (link) interamente dedicato agli studi INAF-OAPA/CfA della regione di formazione stellare nota come Nebulosa dell’Aquila o M16, contenente l’ammasso stellare NGC 6611, realizzato con vari telescopi operativi in diverse bande dello spettro elettromagnetico, tra cui il satellite Chandra della
Most of the exoplanets identified so far have been discovered by using two techniques: transits and radial velocity. In particular, radial velocity method consists in detecting the oscillations of stars around the center of mass common with their planetary systems by measuring periodic doppler shifts in high-resolution spectra. The main difficulty with this technique is the fact that stellar activity,
Some main sequence stars shows an excess of emission in far infrared with respect to photospheric values. This emission is thought to be thermal emission of dust grains and solid bodies associated with a debris disk orbiting around stars. This hypothesis has been confirmed when some of these disks, such as the one orbiting the star Fomalhaut, have been directly
During their short existence lasting only few million years, massive stars (more massive than 8 solar masses with spectral type O and B-early) strongly affect the surrounding environment thanks to their intense UV radiation and stellar winds. A single O star, in fact, can loose about 10-6 solar masses of gas in a wind reaching velocities of 1600–2500 km s−1 (Stevens & Hartwell, 2003).
It has been suggested that stars formed from the same molecular cloud should share the same primordial chemical abundances. This has led several authors to consider the possibility that stars formed in a star forming region now disappeared could be identified by studying their chemical composition (chemical tagging theory, Freeman & Bland-Hawthorn 2002). However, the evolution of chemical abundances of
