Notte Europea dei Ricercatori 2023
In occasione della Notte Europea dei Ricercatori 2022, l’INAF-Osservatorio Astrofisico di Catania ha organizzato varie attività per il pubblico che si svolgeranno tra il 28 e il 30 settembre.
Pagina di caricamento
eventi-seminari
Segnalati
Nati sotto il segno di Dike, cresciuti con quello della Bilancia – La storia della Space Law, tra gravità e giurisprudenza
Sede A. Riccò Via Santa Sofia 78, CataniaIn questo seminario pongo l'attenzione su quei particolari momenti in cui la scienza giuridica ha felicemente intersecato l’osservazione pre-scientifica della natura e, in seguito, le scienze fisiche propriamente dette, traendo da esse, specie nel passato, quando ispirazione, quando una maggiore forza argomentativa.
Si tratta di incroci che sembrano denunciare in modo chiaro un’origine comune dello sguardo del fisico e del giurista - un’origine di sicuro meritevole di uno studio storico e filosofico più attento che già sto conducendo – e che la presente ricerca evidenzia solo per la parte avente a che fare con la descrizione di come la nostra specie si è progressivamente impossessata dello spazio esplorabile: un concetto usato in una fase iniziale esclusivamente per indicare territori sulla terraferma e che, al progressivo crescere delle acquisizioni scientifiche, tecnologiche e di una parallela evoluzione giuridica, ha subito diverse modifiche che gli hanno fatto guadagnare pure il significato di distese marine, di spazi aerei al di sopra delle nazioni e, in tempi più recenti, quello di spazio esterno alla nostra atmosfera. Uno spazio oramai teatro di dispute di diritto internazionale e scenario di possibili scontri bellici del futuro.
Diagnostics of the solar corona expansion through Metis coronagraph observations
Sede A. Riccò Via Santa Sofia 78, CataniaThe solar corona has been investigated in the last decades through observations coming from several spacecraft. The Metis coronagraph, aboard the ongoing Solar Orbiter mission, extends the UVCS/SOHO spectrocoronagraph observations of the scattered ultraviolet emission of the coronal plasma performed during solar activity cycle 23, by simultaneously imaging the coronal visible light polarised brightness (VL pB), in the spectral bandpass 580-640 nm, and the coronal ultraviolet H I Lyα emission, in the spectral window 121.6 ± 10 nm. Here some specific observations are shown, such as those taken on May 15, 2020, from which important results about the solar wind outflow velocity were inferred by applying the Doppler dimming technique. Other results on the coronal solar wind velocity are presented, obtained by considering the data acquired during the first quadrature of the Solar Orbiter and the Parker Solar Probe (PSP) spacecraft with respect to the Sun. In particular, the same parcel of plasma on the East limb was remotely observed with Metis between 3.5 R⊙ and 6.3 R⊙ on January 17, 2021, during low-cadence synoptic mode observations, and was sampled in situ by PSP at about 22 R⊙ on January 18, 2021. In this case, information about several coronal parameters were inferred with unprecedented details, thanks to the high quality of Metis and PSP data. Finally, other results concerning the first coronal mass ejection observed with Metis on January 16-17, 2021 are reported. In this case, also considering data coming from instruments onboard Solar Orbiter and other spacecraft, a 3D reconstruction and detailed physical information about this structure were obtained. Therefore, Metis, even when operates in synoptic mode and in synergistic coupling with other instruments, allows to get novel and detailed information about the structure of the solar corona with an accuracy never reached until now.
Gravitational entropy proposals adaptable to structure formation in Cosmology
Sede A. Riccò Via Santa Sofia 78, CataniaI would like to summarize and present cosmological applications of two proposals of Gravitational entropy, which are distinct from the standard holographic approach and from the entropy of the sources. One is the proposal by Clifton-Ellis and Tabakol (CET) based on the Bel-Robinson tensor, the other by Hosoya and Buchert (HB), based on the Leibler-Kullbach functional of Information Theory. By applying these proposals to inhomogenous dust solutions of Einstein’s equations (LTB and Szekeres models), we have shown in various published articles that both proposals are equivalent in their predictions, but CET is local and HB is non-local. Both yield entropy production in spacetime regions that can be characterized by generation and growth of structure (either overdensities or voids). The CET proposal provides an interesting interpretation of the cosmological constant as an asymptotic gravitational temperature that characterizes a finite entropy saturation value.
Determination of fundamental stellar parameters on massive stars
Sede A. Riccò Via Santa Sofia 78, CataniaMassive stars (i.e. the progenitors of core-collapse supernovae) are quite scarce, but play a crucial role in several important astrophysical phenomena, as for example, the chemical evolution of their host galaxies. Even so, their fundamental stellar parameters (as mass, radii, temperature and luminosity) are poorly known. This relates to important uncertainties about their formation processes, structure and evolution. We are attempting to face this challenge at the research group GEMAE (Grupo de investigación en Estrellas Masivas y Agrupaciones Estelares) at the University of La Plata, together with collaborators in Chile and Spain. We rely mainly on high-quality and high-resolution spectroscopic data collected by 18 years by the OWN Survey of the O-type and WN-stars in the Southern hemisphere. In this talk I will outline the work that we are developing at GEMAE, focusing on determinations of masses of close binary stars by spectroscopy and photometry in the optic and near-infrared bands.
The evolution of young low-mass stars: focus on rotation and activity
Sede A. Riccò Via Santa Sofia 78, CataniaBetween its formation stage as an active accreting seed and today, the Sun underwent large structural changes as well as variation in magnetic activity, rotation rate and its relation to the surrounding environment. I will go through the different processes that are responsible for these changes and present our latest results on the subject. We will go from the early interaction between the star and its proto-planetary disc bathing in UV radiations emitted from the massive neighbours, to the internal mixing happening in the inner layers of solar-like stars that are probed by asteroseismology.
Finally, I will review the possible applications of this work to other types of stars at different stages of the evolution in the context of the current or future surveys.
Challenges for the forthcoming CMB polarization experiments
Sede A. Riccò Via Santa Sofia 78, CataniaOne of the major challenges in the context of the Cosmic Microwave Background (CMB) radiation is to detect a polarization pattern, the so called B-modes of CMB polarization, that are thought to be directly linked to the space-time fluctuations present in the Universe at the very first instants of life. To date, several challenges have prevented to detect the B-modes partly because of the lower sensitivity of the detectors. Our own Galaxy is observed in this context as a foreground contamination. However the awareness of improving the modeling of its polarized emission has been constantly increase not only to assess the cosmological signals but also to provide new insights onto the Galactic magnetic field probed with the Galactic polarized emissions, e.g. synchrotron and thermal dust. This is particularly relevant in order to better characterize the foreground contamination for future CMB experiments (e.g. SO, LiteBIRD, CMB-S4 ), where unprecedented polarization sensitivities are expected to be achieved in the coming decades.
Astronomical Observations & Optical Communication through Atmospheric Turbulence
Sede A. Riccò Via Santa Sofia 78, CataniaThe atmospheric parameters have a strong impact on the image formation through the atmosphere. Indeed, the effect of atmospheric turbulence on wavefronts reduces severely the resolution of ground-based astronomical observations. Thus, in the context of astronomical observations, the site-selection has now become essential with the advent of the next generation of Extremely Large Telescopes (ELT). Indeed, it is important to choose sites with reduced cloud coverage, weak turbulence and low aerosol distribution in order to enhance observations time and to improve their scientific performance. It is also important to remember that the choice of sites hosting astronomical projects must meet very strict criteria in terms of optical quality. Future optical communications and telemetry stations will be forced to meet the same
requirements.
Space-Weathering on Primitive Asteroids
Sede A. Riccò Via Santa Sofia 78, CataniaStudying small bodies in our solar system is fundamental for understanding its youth and evolution. These small "primitive" bodies are "undifferentiated" (they did not undergo phase density separation, irreversibly altering their mineralogy). They have evolved little since their creation, spurring a composition relatively close to the primordial proto-planetary disk. However, other processes, such as thermal alteration, aqueous alteration, shocks, or space-weathering, can affect these bodies' surfaces.
The Gravitational-Wave breakthrough we can(‘t) wait for
Sede A. Riccò Via Santa Sofia 78, CataniaLess than a decade after the first historical Gravitational Wave (GW) detection GW150914, the field of GW astronomy has grown at a phenomenal pace, going from less than an event per month, to the currently observed rate of few events a week.
Despite the exceptional contributions the field has brought to fundamental physics, astronomy, cosmology, computational physics as well as the unavoidable collateral progress in fields related to the experimental development of GW detectors, the picture is anything but complete.
Amongst the missing pieces of the puzzle we find Continuous Gravitational Waves (CGWs).
In this seminar I am going to talk about CGWs, what are they and what astrophysical sources and mechanisms can produce them, with a particular focus on non-axisymmetric spinning Neutron Stars.
I will also briefly discuss the different search implementations, what is done, or can be done, to increase our chances to arrive to what is probably going to be the next breakthrough in GW Astronomy, the first CGW detection, including a discussion about prospects in view of future observation runs as well as GW detectors operational in the close future.