doppler_relativistic#
- astropy.units.equivalencies.doppler_relativistic(rest)[source]#
Return the equivalency pairs for the relativistic convention for velocity.
The full relativistic convention for the relation between velocity and frequency is:
\(V = c \frac{f_0^2 - f^2}{f_0^2 + f^2} ; f(V) = f_0 \frac{\left(1 - (V/c)^2\right)^{1/2}}{(1+V/c)}\)
- Parameters:
- rest
Quantity
Any quantity supported by the standard spectral equivalencies (wavelength, energy, frequency, wave number).
- rest
References
NRAO site defining the conventions
Examples
>>> import astropy.units as u >>> CO_restfreq = 115.27120*u.GHz # rest frequency of 12 CO 1-0 in GHz >>> relativistic_CO_equiv = u.doppler_relativistic(CO_restfreq) >>> measured_freq = 115.2832*u.GHz >>> relativistic_velocity = measured_freq.to(u.km/u.s, equivalencies=relativistic_CO_equiv) >>> relativistic_velocity <Quantity -31.207467619351537 km / s> >>> measured_velocity = 1250 * u.km/u.s >>> relativistic_frequency = measured_velocity.to(u.GHz, equivalencies=relativistic_CO_equiv) >>> relativistic_frequency <Quantity 114.79156866993588 GHz> >>> relativistic_wavelength = measured_velocity.to(u.mm, equivalencies=relativistic_CO_equiv) >>> relativistic_wavelength <Quantity 2.6116243681798923 mm>