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ESP2024 – PLATO PLANETARY SYSTEMS: Formation to Observed architectures

Department of Physics and Astronomy "Ettore Majorana" (DFA) of the Catania University Via Santa Sofia 64, Catania, Italia

PLATO is the 3rd mission of class M in the ESA Cosmic Vision program. Its main goal is detecting terrestrial planets in the habitable zone of solar type stars. With its huge FOV, most of the PLATO targets are bright stars that will be monitored with high cadence (25 s) for at least 2-3 years during the long duration observing program, while contemporary a number of very bright stars in the sample will be observed with 2.5 s cadence. The collected data, photometry from space and high resolution spectroscopy from the ground, will provide accurate planetary structures as well as architectures and evolutionary stage - via asteroseismic analysis - of a large number of planetary systems. PLATO is planned for a launch in Dec 2026.

The Hot Neptune Desert

Sede A. Riccò Via Santa Sofia 78, Catania

The vast majority of close-in planets are either massive hot Jupiters capable of holding their atmosphere against the stellar photoevaporation or small rocky planets completely drained by the stellar radiation. We observe an unexpected dearth of highly irradiated Neptune- and Saturn-like planets orbiting their host star in less than 4-10 days, called "Hot Neptune Desert". In this talk, I will present our recent findings from uniformly vetting 250 hot Neptune TESS candidates using a two-step vetting technique, as well as discuss a cutting-edge approach to examine the problem under a new perspective. I will also discuss how the PLATO mission may enhance our understanding of the Hot Neptunes.
We will present some recent results - obtained by using this updated observational and theoretical framework - about the formation and early evolution of the Milky Way.

How is magnetism affecting the properties of solar and stellar acoustic modes?

Sede A. Riccò Via Santa Sofia 78, Catania

Outside of solar neutrinos, the only way to directly probing solar and stellar interiors is to use seismic techniques, i.e. studying the waves propagating inside them. In the case of the Sun, acoustic waves are excited by turbulent motion in the convective envelope, and propagate towards the interior, creating a variety of standing pressure modes (p modes). By investigating how small perturbations influence the modes parameters, it is possible to probe the structural and dynamical properties of the star such as internal rotation and mixing, chemical composition, density, convection zone depth, etc. In the stellar case, asteroseismology allows the inference of the stellar fundamental parameters such as mass, radius, and age. Although, solar p-modes frequency, amplitude, and energy vary in relation with the solar magnetic cycle and similar variations were observed for other magnetically active solar-type stars, such a variability is often overlooked in stellar modelling. In the context of the preparation of the PLATO mission, whose aim is to characterize Earth-like planets orbiting solar-like stars in part thanks to asteroseismology, we need to better understand the relation between magnetic variations and modes parameters. In this seminar, I will focus on the excitation of the solar p modes using the last 28 years of data from the SoHO/GOLF instrument, with a method gathering a better temporal resolution compared to classical approaches. In this framework, I was able to perform a statistical study of the energy of the modes. Summing the energy of all studied modes, I will demonstrate that there is a discrepancy between the observed excitation rate and the expected rate under the hypothesis of excitation driven entirely by turbulent convection. I will discuss the link between this discrepancy and surface magnetism effects such as flares and coronal mass ejection. In conclusion, I will explain how a better understanding of the relation between the dynamo mechanism and modes properties variation across time would allow us to improve the constraint we have on stellar dynamics and obtained refined stellar fundamental parameters.

Magnetic activity nesting on the Sun and low-mass stars: Results from nearly continuous monitoring of solar active nests with ESA’s Solar Orbiter

Sede A. Riccò Via Santa Sofia 78, Catania

The magnetic activity of low-mass stars, driven by the interplay of convection and rotation in their interiors, is fundamental to their evolution and significantly affects the search for habitable exoplanets. Magnetic activity manifests at the surface as "spots" (or active regions) that influence the circumstellar environment through energetic radiation and eruptive events (flares and coronal mass-ejections, collectively termed “space weather”). The Sun exhibits a well-known 11-year activity cycle where spot emergence drifts from mid to low latitudes. However, one puzzling feature of the solar dynamo is the repeated emergence of spots in close proximity, which leads to long-lived sources of magnetic activity known as active nests. Nesting is observed on other low-mass stars, suggesting it is an innate, universal feature of stellar dynamos. It is theorized that non-axisymmetries in the generation and storage of the magnetic field preference the emergence of spots at specific latitudes and longitudes, leading to nesting. This phenomenon has consequences for predicting space weather near Earth and understanding the secular evolution of exoplanetary atmospheres. Studies of solar active nests have been limited by our single viewpoint from Earth. But with ESA’s Solar Orbiter now monitoring the Sun's far-side for several months each year, multi-viewpoint observations provide a pathway to study the formation and evolution of active nests. So far we have identified an active nest in 2022 that was responsible for 50–70% of all solar flares across the entire solar surface over five months (a prolific flare factory). In addition, we saw a dramatic intensification of solar flare activity in 2024 following the collision of two active nests. These continuous, multi-viewpoint observations strengthen the connection between solar activity and the nesting observed on other low-mass stars, a link that will be further explored with ESA’s PLATO mission.