Every second, a trillion of the elusive ghost particles, the neutrinos, pass straight through your body. Now, astrophysicists from the University of Copenhagen have mapped how many ghost particles all the stars in the Milky Way send towards Earth, and where in the galaxy they originate. This new map could help us track down these mysterious particles and unlock knowledge about our Galaxy that has so far been out of reach.

Neutrinos are produced during stellar evolution by means of thermal and thermonuclear processes. We model the cumulative neutrino flux expected at Earth from all stars in the Milky Way: the Galactic stellar neutrino flux (GS$ν$F). We account for the star formation history of our Galaxy and reconstruct the spatial distribution of Galactic stars by means of a random sampling procedure based on Gaia Data Release 2. We use the stellar evolution code $\texttt{MESA}$ to compute the neutrino emission for a suite of stellar models with solar metallicity and zero-age-main-sequence mass between $0.08M_\odot$ and $100\ M_\odot$, from their pre-main sequence phase to their final fates. We then reconstruct the evolution of the neutrino spectral energy distribution for each stellar model in our suite. The GS$ν$F lies between $\mathcal{O}(1)$ keV and $\mathcal{O}(10)$ MeV, with thermal (thermonuclear) processes responsible for shaping neutrino emission at energies smaller (larger) than $0.1$ MeV. Stars with mass larger than $\mathcal{O}(1\ M_\odot)$, located in the thin disk of the Galaxy, provide the largest contribution to the GS$ν$F. Moreover, most of the GS$ν$F originates from stars distant from Earth about $5-10$ kpc, implying that a large fraction of stellar neutrinos can reach us from the Galactic Center. Solar neutrinos and the diffuse supernova neutrino background have energies comparable to those of the GS$ν$F, challenging the detection of the latter. However, directional information of solar neutrino and GS$ν$F events, together with the annual modulation of the solar neutrino flux, could facilitate the GS$ν$F detection; this will kick off a new era for low-energy neutrino astronomy, also providing a novel probe to discover New Physics.