Earth is rotating around its axis with a period Tm≈\SI24h. The Sun is also rotating around its axis. That can be proven for example by observing the motion of sunspots but in this exercise we use the information of the spectrums radiated by equatorial points A and B located on the edge of the Sun’s disc. It turns out that measuring the wavelengths of sodium’s yellow absorption line yields slightly different values for the points A and B. The measured wavelengths differ from each other by Δλ=\SI7.8pm=\SI7.8e−12m. The laboratory measured wavelength of sodium’s yellow absorption line is λ0=\SI590nm, the speed of light c=\SI3.0e8m/s, the Sun’s radius r=\SI700000km. Find the rotation period Tp of the Sun’s equatorial area.