An astronomer observing the spectrum of the Sun on the solar equator finds that the Balmer H _$\beta$ spectral line ($\lambda$ = 486 nm) is blueshifted by 0.0033 nm when measured at one edge of the Sun's disk compared with the same line at the center of the Sun's disk and is redshifted by the same amount on the equator at the other side of the Sun's disk. If this Doppler shift is due to the Sun rotating (try drawing a diagram), then the rotational speed of the Sun at its equator is A) 1 km/s. B) 0.5 km/s. C) 2 km/s. D) 4 km/s.

Question

Quizplus · Accepted Answer

The Doppler shift formula for velocity is $v = \frac{\Delta \lambda}{\lambda}c$, where $\Delta \lambda = 0.0033 \, \text{nm}$, $\lambda = 486 \, \text{nm}$, and $c = 3 \times 10^8 \, \text{m/s}$. Substituting these values gives a rotational speed of approximately 2 km/s for the Sun at its equator.

An Astronomer Observing the Spectrum of the Sun on the Solar