Zollner
NAME: Zollner, Johann Karl Friedrich
ACHIEVEMENT(S): Astrophotometer
NICKNAME/ALIAS: None
DATE/PLACE OF BIRTH: 8 November 1834, at Berlin, Germany
DATE/PLACE/AGE AT DEATH: 25 April 1882, in Leipzig, Germany. aged 47
DISCIPLINE: Astrophysicist
FIELD: Astrophysics
LANGUAGE: German
PARENTS: ?
SIBLINGS: ?
SPOUSE: ?
CHILDREN: ?
EDUCATION: University of Berlin, 1855-57; University of Basel, 1857-59
MAJOR WORK: 'Photometric Studies with Special Consideration of the Physical Nature of the Heavenly Bodies', 1865
LIFE AND TIMES: Karl Friedrich Zollner was the son of a pattern-maker and cotton-printer. As a youth, Zollner showed a talent for constructing instruments and doing experiments, but on his father's death in 1853 he was obliged to take over the management of the family factory.
Within a year, having proved himself a poor businessman, he had returned to school, and in 1855 he entered the University of Berlin to study physics and other sciences. In 1856 he published his first work, a study of photometry and photometers, by which the brightness of stars and other celestial objects are measured, and he had also begun work on the development of electric motors.
During his vacations, Zollner built a small private observatory in the tower of his father's factory in Schoneweide (now part of Berlin), where he then tested his ideas on the photometry of celestial bodies. In 1857 he moved on to the University of Basel, where he was taught by G.H. Wiedemann, and where in 1859 he received his Ph.D. for a dissertation on photometric problems.
While at Basel, Zollner had made a chance observation which gave him an idea
for a greatly improved photometer, based on that designed by <improved on work of> Steinheil* in Munich in 1842.
He then built his innovative astrophotometer, a device for measuring the brightness of stars and other celestial objects, which he then had constructed in 1860 in the Kern optical and mechanical workshop in Aarau.
Using this instrument, which created an image of an artificial star by which the brightness of each real star under observation could be compared, Zollner investigated fundamental problems of photometry, made comparisons of other photometers, and soon amassed a
large amount of data which he wrote up and submitted to a competition held
by the Vienna Academy of Sciences.
Although the jury found that Zollner had not measured the brightness of enough stars to receive the prize, his entry - which he published in 1861 - has proved to be a classic of astrophysics. Here Zollner first described his astrophotometer, which was then widely used.
In 1862, Zollner moved to Leipzig, where he published 'Photometric Studies with Special Consideration of the Physical Nature of the Heavenly Bodies' (1865), which contains his: "Theory of the Relative Brightness of the Phases of the Moon."
In 1866 Zollner was appointed professor of astronomy at the University of Leipzig, and in 1869 invented the reversion spectroscope, which made possible the most detailed observations of spectra (the arrangement according to wavelength of visible, ultraviolet and infrared light) so far.
Based on the principle of the heliometer, in Zollner's spectroscope two beams passed through two direct-vision prism systems arranged so that the dispersion within them occurs in mutually opposed directions. With this Zollner planned to improve the measurements of Doppler shifts in the spectra of objects with velocities having a high radial component, and Hermann Vogel used the spectrometer to determine the rotational velocity at the solar equator.
In the late 1860s Zollner also designed his horizontal pendulum, with which he was able to observe and study solar protuberances, for which he was elected a member of the Saxon Academy of Sciences at
Leipzig.
During this period Zollner also made an intensive study of solar theory, sunspots, solar rotation, and <studied> Olbers’* paradox. In 1870 he published: "On the Influence of Density and Temperature on the Spectra of Glowing Gases" and in 1873 produced a work on comets, in which he correctly assumed that elements of the nucleus of a comet gradually vaporize as it nears the Sun.
In 1875 Zollner travelled to London, where he met <spiritualist with> Crookes* and began an intensive study of Spiritualism, to which he soon became a convert. Although this development upset the majority of his friends and colleagues, through Spiritualism he became friendly with German scientists <a pal of> Fechner* and <a pal of> WE Weber*.
In 1880 he published an attack on the scientific community, which further alienated him from his immediate colleagues. He died while editing the preface to the third edition of his book on comets.
ASSESSMENT: Karl Friedrich Zollner was a mid-19th-century pioneer in astrophysics who greatly advanced the use of photometry and made important technological contributions to science
EXTRA CONNECTIONS: <work related to> Leavitt* used a development of his astrophotometer
ONELINER: Karl Zollner, who developed the astrophotometer
BIBLIOGRAPHY:
DSB