William Huggins

Sir William Huggins was a wealthy amateur astronomer who, together with his wife Margaret, transformed astronomy from a science of positions and motions into one that could determine what celestial objects are made of. From his private observatory in Tulse Hill, London, he became one of the first to apply spectroscopy to the stars. In 1864, Huggins made a landmark discovery: examining the spectrum of the Cat's Eye Nebula (NGC 6543), he found it showed bright emission lines rather than a continuous stellar spectrum. This proved that at least some nebulae were clouds of luminous gas, not unresolved star clusters — settling a debate that had raged for decades. He went on to identify hydrogen, sodium, calcium, and other elements in the spectra of stars, demonstrating that the same chemical elements found on Earth exist throughout the universe. With Margaret, he pioneered the use of dry-plate photography for recording stellar spectra.

• Proved that some nebulae are gaseous, not stellar (1864) • Identified chemical elements in stellar spectra • Pioneered the use of the Doppler shift to measure stellar radial velocities • First to photograph the spectrum of a star • Demonstrated the universality of chemical elements across the cosmos