Calendar

ABSTRACT:

Only a very small fraction of the organic compounds in nature are found in planets or comets and other  condensed objects. By far the larger quantity, more than 99.9% by mass, reside in the enormous molecular clouds in interstellar space of the Milky Way and other galaxies. Abiotic organic chemistry, as observed in molecular clouds, offers a glimpse of the chemical evolution preceding the onset of life on our own planet,  and allows us to evaluate the possibility that – during the evolution from a molecular cloud to a planetary system – complex organic molecules are formed, transformed and preserved until they are incorporated into comets and meteorites. The analyses of such cosmic debris show that some of the amino acids present an excess of the L-conformation enantiomer in straightforward similarity with terrestrial biomolecular homochirality. This coincidence is too striking to be fortuitous; it points out that products of routine cosmic chemistry contributed to the early Earth organic pool and facilitated prebiotic molecular evolution.

Among the many scenarios put forward to explain the origin of chiral homogeneity, one involves the asymmetric photolysis of amino acids present in space, triggered by circularly polarized ultraviolet radiation.
Here we propose that amino acids formed in the cavities of interstellar dust aggregates are
exposed to asymmetric photolysis induced by an effective ultraviolet circularly polarization generated in situ.

Visita delle studentesse del corso di laurea in Conservazione e Restauro dei Beni Culturali, accompagnate dal docente Marco Di Bella

a cura di Donata Randazzo e Giada Genua

Questo meeting è organizzato allo scopo di mettere assieme idee e progetti di ricerca che comprendano l’utilizzo del secondo Data Release di Gaia.

L’idea è che chiunque abbia un progetto da presentare o discutere prepari una piccola presentazione, meglio utilizzando qualche immagine, e lo comunichi a Mario Guarcello (), che preparerà una scaletta dell’incontro.

Planets in short-period orbits provide a unique opportunity to directly study atmospheric escape, which is a phenomenon having a profound impact on our understanding of the observed exoplanet demographics. Among all planets known to have an escaping atmosphere, those undergoing extreme mass loss are key: their escape may be representative of young planets, at a time when atmospheric escape matters most. I will review results obtained from the analysis of Hubble Space Telescope observations, particularly those of the extreme hot Jupiters WASP-12b, WASP-13b, and WASP-18b. I will then show how planet atmospheric escape may be at the origin of the correlation between the chromospheric activity of stars hosting hot Jupiters and the planets’ surface gravity. I will finally show how planets orbiting early-type stars might become of crucial importance in the near future and how their escaping atmospheres can be observationally studied.

Il ritorno di fiamma della teoria circa l’esistenza del pianeta X (o IX…) fornisce una ghiotta occasione per porsi una domanda che potrebbe avere una certa rilevanza: è il pensiero scientifico un “a priori” rispetto alla capacità di elaborare narrazioni o vale invece l’inverso, ovvero che prima di arrivare ad applicare una corretta analisi empirica, necessitiamo di strutture narrative utili a delimitare e arricchire di significati il contesto nel quale le ulteriori analisi scientifiche verranno effettuate? La presente ricerca rappresenta lo sviluppo di un’idea già presente in “Pianeti tra le note”, un mio libro già presentato a Venezia, nella sessione poster dell’INSAP VI nel quale veniva proposto un diagramma quasi analitico della distribuzione delle narrazioni di qualsiasi tipo in funzione della distanza dal Sole. Per effettuare tale sviluppo mi sono servito di una attenta analisi cronologica del concetto di “ulteriore pianeta” del sistema solare così da tentare di capire se l’idea sia da considerarsi ancora in una fase narrativa o se si tratta di qualcosa già appartenente all’ambito scientifico. La domanda forse poco fondamentale giunge infine a quella essenziale: “cosa è la scienza?” alla quale tento di dare una risposta.

The comprehension of magnetically-related phenomena occurring in stellar atmospheres is one of the long-standing issues of astrophysics. The solar corona has always been the starting point to understand coronal physics, because the high spatial structuring of coronal plasmas complicate stellar observations. Stars however show activity levels up to 10^4 times higher than the Sun, and it is not clear how the different magnetic phenomena scale with the activity level. Therefore, direct observations of the different magnetic phenomena in active stars are crucial. However, many of them, among which are coronal mass ejections (CME), remain observationally unexplored. By performing time-resolved X-ray spectroscopy of a stellar flare, we present here the direct and unambiguous evidence of upward and downward motions of plasma within the flaring loop, and, most notably, also of the subsequent CME. The observed motions within the flaring loop neatly agree with hydrodynamic (HD) model predictions, indicating that the standard flare model holds also for flares 10^4 times more energetic than the most intense solar ones. This first direct and clear observation of a stellar CME allows us to infer its mass and kinetic energy. These findings provide crucial clues in the extrapolation of the solar case to higher activity levels, indicating that, in active stars, the kinetic energy loss due to mass expulsion appears considerably less effective.