REVealing the Effects of Star-planet Interactions

Project Information

REVErSI

Grant agreement ID: 101030103

DOI

10.3030/101030103

Project closed

EC signature date 13 March 2021

Start date 1 December 2021

End date 30 November 2024

Funded under

• EXCELLENT SCIENCE - Marie Skłodowska-Curie Actions

Total cost

€ 259 398,72

EU contribution

€ 259 398,72

Coordinated by

AGENCIA ESTATAL CONSEJO SUPERIOR DE INVESTIGACIONES CIENTIFICAS
Spain

Periodic Reporting for period 1 - REVErSI (REVealing the Effects of Star-planet Interactions)

Reporting period: 2021-12-01 to 2024-11-30

Summary of the context and overall objectives of the project

The discoveries of the first planets outside the Solar System in the 1990s opened the completely new
research topic of exoplanetary science. Since then, the existence of over 4300 exoplanets has been
confirmed and exoplanetary science has become one of the main branches of astrophysics.
Exoplanets are discovered with several techniques providing complementary information on the
objects: transit photometry can unveil the planet’s radius, while the radial velocity technique can give
estimates of the planet’s mass. New insights on exoplanet characterization will soon come also from
space missions like TESS, CHEOPS (already online) and JWST and PLATO (planned).
However, two of the most critical aspects of exoplanetary systems remain very difficult to assess:
1) The magnetisation of exoplanets, which plays a central role in planetary habitability. A planetary
magnetic field shields the planetary surface from the destructive flux of charged particles of stellar
winds, so that life can evolve. Knowing planetary magnetism it is necessary to understand exoplanetary
climates and address exoplanetary habitability.
2) The interaction between the planet and its host star, which is mediated by gravitation, radiation,
magnetic fields, and the stellar wind. While it is clear that these star-planet interactions (SPIs) affect the
planet, it is unclear whether they have an observable effect on the star. Understanding the physics
governing SPIs is essential to push exoplanetary science into the next era.
REVErSI is an ambitious project that aims to provide access to these two characteristics for the first
time. By developing analytical and numerical models of SPIs, and constraining them on available stellar
observables, this project unravels the effect of magnetic and tidal SPIs on the activity of the
host star. As a second step, REVErSI will use models of magnetic SPI to predict the magnetic field
strength of some exoworlds.
Being able to characterize exoworlds is central for the human need of exploring and discovering the universe. Ask any kid around the world, or almost any kid, and they are fascinated by understanding remote areas of the universe where, possibly, life exists. This project is a step in this direction.

Work performed from the beginning of the project to the end of the period covered by the report and main results achieved so far

The work performed was of theoretical, numerical and observational nature.

The theoretical work consisted in developing models that can serve alone by understanding the magnetization of exoworlds.
Also, it was the basics of the numerical work performed in the second phase.
The numerical part of the project was probably the most bulky. We performed numerical simulations of systems able to amplify magnetic fields in planets and stars.
Our models, performed with two different codes, shows the importance of the turbulent aspect of the fluids which constitute planets and stars, the importance of shearing conditions that can arise from tidal interaction, as well as the importance of radial structure and convection for what concern planets.

Last, the observational part: we undertook several observations of exoplanetay systems that can display star-planet interactions. We have some tentative discovery in the radio wavelength, and some more are currently under revision. Also, by examining spectra of nearby systems, we were able to uncover the existence of new planets that have already become object of follow up campaigns for trying to detect imprints of star-planet interactions.

The science started with this project does not stop here since more observations are planned, more numerical work is being performed also after the end of the project and new results are currently under revision in peer review journals.
The dissemination of these results took place in several international conferences in Europe and the Americas, as well as in work visits and invited colloquia. Last but not least, the PI took part to several outreach initiatives, one of which will take place in the next MArch in Brusselcs and it is connected with MSCA (Science is wonderful initiative)

Progress beyond the state of the art and expected potential impact (including the socio-economic impact and the wider societal implications of the project so far)

The most crucial development beyond the state of the art was probably the observational part in the radio wavelength. We observed several exoplanetary systems to emit coherent radio emission that can be connected and explained by the presence of magnetic fields providing interaction between the planet and its host star. this was unprecedented and it is, matter of fact, still debated, but it is clear that we uncovered some scientific aspect that was previously unknwon.
the impact on the society is the possibility, for the first time, to claim that some exoplanetary system is characterized by a certain type of magnetism, which, in turn, can be crucial for providing conditions allowing the existence of life on such exoworlds. the implication of such discoveries therefore go well beyond astronomy.

Magnetic field simulated for an extrasolar planet