Portrait of the British astronomer Sir William Huggins, 1824-1910. Huggins was a wealthy amateur who had his own observatory in South London. He pioneered the study of the spectra of stars, finding them to contain elements already known on the Earth and in the Sun. He discovered that nebulae were composed of luminous gas, and found that comets contained hydrocarbon molecules. In 1868 he observed that the spectrum of Sirius is shifted towards the red end of the spectrum. He correctly interpreted this as being due to the Doppler effect as the star moves away from the Earth; he used the degree of shift to determine the velocity of Sirius and many other stars.