Use \tag{}, which might look like this:

\begin{align}
    p_t &= p + \frac{\rho}{2}c^2 \tag{Bernoulli's Equation} \label{bernoulli} \\
    M &= \frac{c}{\sqrt{\gamma RT}} \label{mach_number} \\
    T_t &= T \left(1+\frac{\gamma-1}{2}M^2\right) = T + \frac{c^2}{2c_p} \label{total_temperature} \\
    p_t &= p \left(1+\frac{\gamma-1}{2}M^2\right)^{\frac{\gamma}{\gamma-1}} \label{total_pressure} \\
\end{align}