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_Excerpt taken from [Supernova Neutrinos](https://neutrino.leima.is/book/introduction/supernova-neutrinos/)_
### Markdown
```md
The average energy of the neutrinos $\langle E \rangle$ emitted during a supernova explosion is of the order of 10MeV, and the neutrino luminosity at the early epoch of the explosion is approximately $10^{52}\mathrm{ergs\cdot s^{-1}}$.
Therefore, the number density of the neutrinos at the radius $R$ is
$$
\begin{equation*}
n \sim 10^{18} \mathrm{cm^{-3}} \left(\frac{100\mathrm{km}}{R}\right)^2 \left(\frac{10\mathrm{MeV}}{\langle E \rangle}\right).
\end{equation*}
$$
```
### HTML
The average energy of the neutrinos $\langle E \rangle$ emitted during a supernova explosion is of the order of 10MeV, and the neutrino luminosity at the early epoch of the explosion is approximately $10^{52}\mathrm{ergs\cdot s^{-1}}$.
Therefore, the number density of the neutrinos at the radius $R$ is
$$
\begin{equation*}
n \sim 10^{18} \mathrm{cm^{-3}} \left(\frac{100\mathrm{km}}{R}\right)^2 \left(\frac{10\mathrm{MeV}}{\langle E \rangle}\right).
\end{equation*}
$$
It turns out that the ambient dense neutrino medium has a significant impact on neutrino oscillations, which has been intensely investigated in the last decade.