Charles A. Young (1834–1908)

Charles Augustus Young was born at Hanover, New Hampshire, on 15 December 1834. Both his father and grandfather had been Professors of Mathematics and Natural Philosophy at Dartmouth College, where Young entered in 1849 at age fourteen and graduated from in 1853 at the head of his class. A modest and pious man, Young first contemplated missionary work, but in 1856 accepted a position at Western Reserve College (Ohio) as professor of Mathematics, Natural Philosophy and Astronomy. In 1866 he took the position at Dartmouth College held by his father until the later's death in 1858. In 1877 he became Professor of Astronomy at Princeton University, where he spent the rest of his professional career.

Charles Augustus Young image
Portrait of Charles A. Young (1834–1908).
Credit: Wikipedia.

Young was a pioneer in many field of solar physics and astrophysics. In 1870 he captured the first photograph of a solar prominence. In 1873, he became the first to successfully use diffraction grating for astronomical purposes, which he used in 1876 for one of the earliest measurement of the sun's rotation via the Doppler shift of spectral lines. Heading eclipse expeditions around the world and at high mountain altitudes, Young broke new ground in his spectroscopic studies of the solar outer atmosphere. One of his most far-reaching spectroscopic achievements came in at the 1870 eclipse in Spain, where he discovered the so-called reversing layer in the Sun's chromosphere. The existence of this layer was hotly contested at the time, especially by the British solar spectroscopist Joseph Norman Lockyer. In 1869, working in collaboration with William Harkness, he discovered a green line in the coronal spectrum, without any known counterpart in laboratory spectra. This led the two researchers to propose the existence of a new chemical element hitherto unknown on Earth, which they named "Coronium". It took over 60 years for solar physicists to finally realize that the (in)famous green line belonged in fact to a highly ionized state of Iron, and indicative of the million-degree high temperature of the solar corona.

Young was a highly appreciated and respected teacher at both Dartmouth and Princteon, and an extremely active public speaker on matters of science and astronomy. He published numerous textbooks, including, in 1881, one of the best solar physics textbooks of the period, entitled simply "The Sun", which saw many subsequent editions and translations well into the twentieth century. His very popular 1902 "Manual of Astronomy", an intermediate level textbook, also underwent numerous reprints, including a 1926 edition revised by Henry Norris Russell.

Young was awarded numerous honorary degrees and prizes in the course of his career, including the Janssen Medal of the French Academy of Sciences (1891) for his work in solar spectroscopy. He was a member of the National Academy of Sciences, of the American Philosophical Society, and associate member of the British Royal Astronomical Society. In declining health, Young retired from Princeton in 1905 and moved back to his native Hanover, where he died on 3 January 1908.

Bibliography:
Poor, J.M. 1908, Popular Astronomy, 16(4), p. 218.

Porter, R. (ed.) 1994, The Biographical Dictionary of Scientists, Oxford University Press.