The Institute of Space Sciences (ICE-CSIC), from the Spanish National Research Council (CSIC), an agency of the Ministry of Science, Innovation and Universities, has received an ERC Synergy grant from the European Research Council (ERC) for a project that it is co-leading with scientists from other European institutions. This project aims to revolutionize our current understanding of the Sun. With a budget of €14 million, LUNANOVA will eliminate the current uncertainty in nuclear physics regarding the solar model.
The LUNANOVA project is led by Daniel Bemmerer from Helmholtz-Zentrum Dresden-Rossendorf (HZDR; coordinating) in Germany, Alba Formicola from Istituto Nazionale di Fisica Nucleare (INFN), Gianluca Imbriani from Università degli studi di Napoli Federico II, both in Italy, and Aldo Serenelli, director of the Institute of Space Sciences (ICE-CSIC) in Spain. ERC Synergy Grants fund collaborations between scientific teams working together to solve ambitious and complex research problems that could not be tackled individually.
The Sun we know
Deep inside our Sun, nuclear reactions burn hydrogen, the lightest chemical element, to helium, the second lightest. These fusion processes and their implications are described in the so-called standard solar model. This model is the blueprint for understanding thousands of solar-like stars. For the Sun, the model can be validated by observations of solar neutrinos, of seismic waves at the solar surface, and of the elemental abundances in the solar atmosphere.
However, there is a surprising problem: the computer model of our Sun is much less precise than these very difficult observations. To put it figuratively, the solar model is standing on its head (the observations), not on its feet (the input physics). A fundamental reason for this problem lies in the uncertainties of nuclear physics.
Towards a new model of the Sun
Starting in 2026, LUNANOVA aims to solve this problem. The four lead scientists and their teams will perform accelerator experiments deep underground at the Gran Sasso National Laboratory of the National Institute for Nuclear Physics, in Italy; at the Felsenkeller laboratory in Dresden, and at other labs in Germany and Italy. They will study the solar fusion reactions. The group will interpret their data first in the nuclear context and, subsequently, in the solar and astrophysical contexts, informing a completely new solar model. Over a time span of six years, LUNANOVA will thus remove the now-dominant nuclear physics uncertainty from the solar model.
“LUNANOVA comes at the right time. PLATO, ESA's M3 mission for planet hunting and asteroseismic characterisation of solar-like stars will fly at the end of 2026, and a large part of its core science program focuses on stars slightly more massive than the Sun, the right spot in which the nuclear reactions that are the core science of LUNANOVA matter most”, says Aldo Serenelli, researcher at the ICE-CSIC and the Institute of Space Studies of Catalonia (IEEC).
At ICE-CSIC, Serenelli will be leading the solar and stellar modeling efforts, in a continuous cross-talk with the nuclear reaction experiments at Gran Sasso, Felsenkeller and other experiments. By eliminating nuclear cross sections as a dominant uncertainty in solar and stellar models, LUNANOVA will pave the way for a new qualitative understanding of the physics of solar and stellar interiors.
“Moreover, neutrino and direct dark matter detection experiments under development will provide precise measurements of solar neutrino fluxes that, combined with the new generation of solar models coming from LUNANOVA, will offer unprecedented information about solar composition, the yardstick for most of cosmic chemical abundance measurements, radiative opacities in conditions not achievable in terrestrial labs, and mixing processes in stars”, concludes Serenelli.
