Astronomy Bio...Edward C. Pickering

Jay Bitterman

Edward Charles Pickering was born on July 19, 1846, in Boston, Massachusetts. In 1865 he obtained his B.S. degree from Harvard and became an assistant instructor of mathematics at the Lawrence scientific school at Harvard. Two years later he became an assistant professor of physics at the newly founded Massachusetts Institute of Technology. From 1867 to 1876 he was a full professor of physics at Massachusetts Institute of Technology. In 1869 he set up the first physics laboratory for instruction in the United States. From 1876 to 1918 he was director of the Harvard College Observatory, where he actively encouraged women to take up astronomy as a career. In 1891 he established and equipped a branch observatory to study and photograph southern stars at Arequipa, Peru.

He introduced the meridian photometer to establish the first great photometric catalog of magnitudes, "The Harvard Photometry", containing 4,260 stars that was published in 1884. Pickering based his photometric work on two critical decisions. First, he used the scale of magnitude suggested by Norman Pogson in 1854 in which a change of one magnitude equaled a change by a factor of 2.512 in brightness. Second, he used the Pole Star (Polaris), then considered to have a constant brightness, as the reference standard magnitude and arbitrarily giving it a value of 2.1. He then redesigned the photometer to reflect a number stars around the meridian at the same time so the comparisons were immediately visible. This photometric work continued for the next twenty-five years. Subsequently, Polaris was unfortunately found to vary in brightness to a small degree. It is estimated that he made more than 1.5 million photometric readings.

In 1886 he received funds from Henry Draper's widow, Anna Palmer Draper, to establish the Henry Draper fund. Pickering photographed, classified and measured the spectra of the stars. His research into stellar spectroscopy was conducted using his photometer because it could simultaneously survey the spectra of many stars. He hired Williamina Fleming, Annie Jump Cannon, Antonia Maury and Henrietta Leavitt as observers.

He repeated the brightness measurement of each star twice to be confident of its accuracy. In 1908 these photometric studies were published in the Revised Harvard Photometry, found in Volumes 50 and 54 of the "Annals of College Observatory" which tabulates the magnitudes of over 45,000 stars brighter than the seventh magnitude. It continued to be the standard reference until photographic methods largely replaced the visual ones. In 1918, the complete Draper Catalogue having the spectra of more than 225,000 stars was published. They were classified using a refined alphabetical system that was devised by Annie Cannon.

In 1903 Pickering published the first Photographic Map of the Entire Sky. It contained 55 plates of stars as dim as twelfth magnitude. They were photographed at both Harvard and it's Southern Hemisphere Observatory at Arequipa, Peru by its director, William Pickering, Edward's younger brother. His 300,000-photograph plate library at Harvard of huge areas of the sky has been an invaluable aid to astronomers that are searching for changes in the brightness and the position of celestial objects.

One of Pickering's most notable contributions, in 1890, was an astronomical color index. The perceptible color of a star gave an indication of its temperature.

Both Pickering and Herman Carl Vogel independently detected the first spectroscopic binary stars. He discovered a new series of spectral lines that was due to ionized helium. He continually encouraged amateur astronomers and founded the American Association of Variable Star Observers.

He is honored by having both a Lunar and Martian crater named for him, plus the minor planet Pickeringia. For his remarkable work in astronomical physics he was awarded the Henry Draper Medal in 1888, the Rumford prize in 1891, the Bruce Metal in 1908, and the Royal Astronomical Society's Gold medal in 1901. Pickering died in 1919.