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Sir Frederick William Herschel

discoverer of Uranus

Sir Frederick William Herschel

Friedrich Wilhelm Herschel was born in Hanover, Germany, on November 15, 1738. His father was a musician in the Hanoverian guard, and in 1757 Friedrich was sent to England to earn his living as a musician. (At the time, the crowns of England and Hanover were united under King George II). He learned English quickly and, at age nineteen, he changed his name to Frederick William Herschel.

Herschel became a successful music teacher and bandleader, and played the violin, oboe, and organ. He also composed numerous musical works, including twenty-four symphonies, several concertos, and some church music. After a career leading orchestras in Newcastle, Leeds and Halifax, he became organist of the Octagon Chapel in Bath. Music was never Herschel's greatest interest, however, and once established in Bath he turned to his true passion -- astronomy. In 1772 he was joined in Bath by his sister Caroline, who came to share his interest in astronomy, and the two worked closely together the rest of their lives.

Unable to obtain a good telescope, Herschel decided to construct his own and, in 1774, had the satisfaction of viewing the heavens with a 6-foot telescope made by his own hands. He then set out on a mission to survey the entire heavens, and, if possible, to ascertain the plan of their general structure. For this he required adequate instruments, and he, his brother and his sister spent hundreds of hours grinding and polishing hundreds of specula. He used these instruments to observe the Moon, to measure the heights of lunar mountains, and to begin a catalog of double stars.

In 1781, Herschel communicated to the Royal Society the first of a series of papers on the rotation of the planets and of their several satellites; this series would eventually encompass seven papers, presented between 1781 and 1797. While engaged in those studies Herschel also noticed a white spot near to each of the poles of the planet Mars. Finding that the inclination of Mars' axis to the plane of its orbit differed little from that of the earth, Herschel concluded that Mars' changes of climate would resemble those of Earth, and that the white spots were probably polar snow.

On March 13, 1781, Herschel made a discovery which would allow him to continue his astronomical studies as a profession. While conducting one of his methodical reviews of the heavens -- using a 7-foot reflector with an aperture of 6 inches -- he happened across an object moving outside the orbit of Saturn. Ascertaining that the object was a "new" planet, he dubbed it Georgium Sidus; today we know the object as the planet Uranus. Between 1781 and 1815 he would communicate seven memoirs on the planet to the Royal Society, including two in which he reported his discovery of two Uranian satellites (subsequently named Titania and Oberon). For his discovery, Herschel was awarded the Copley Medal of the Royal Society, elected a fellow, and, in 1782, became private astronomer to King George III. Although he was now able to concentrate on his astronomical studies, he had to supplement his income by making and selling telescopes. The necessity for this interruption in his observations was overcome in 1788, when he married the wealthy widow of a London merchant.

One of the tasks that Herschel set for himself was to determine the relative distances of the stars from our sun and from each other. Observing many stars in apparently very close proximity to each other, but often differing greatly in relative brightness, he concluded that, on the average, the brighter star would be the nearer to us, the fainter enormously more distant. In 1782, he presented a memoir to the Royal Astronomical Society in which he suggested that stars which appeared to be in very close proximity to each other might actually be "double stars" in mutual revolution. In 1793, he remeasured the relative positions of many such double stars and concluded that some of the stars did indeed circulate round each other. This discovery, announced in 1802, immortalized Herschel's place in the history of astronomy.

In a series of papers written between 1784 and 1818, Herschel used his method of star-gauging and concluded that our sun was a star situated not far from the bifurcation of the Milky Way, and that all the stars visible to us lie more or less in clusters scattered throughout a comparatively thin, but immensely extended stratum. On either side of this assemblage of stars, he discovered a canopy of discrete nebulous masses, such as those from the condensation of which he supposed the whole stellar universe to have been formed.

During the course of his career, Herschel constructed more than four hundred telescopes. The largest and most famous of these was a reflecting telescope with a 40-foot focal length and 4-foot aperture, which he completed at his home in Slough, England, on August 28, 1789. The first sight he focused on that night was the Saturnian system. Five of Saturn's moons had been known for quite some time, but Herschel had discovered a sixth (Mimas) two years before, using a little telescope of 6 inch aperture. Now, however, he was able to see that moon in unmistakable brightness. On September 17, using the same telescope, he discovered a seventh moon (Enceladus). The huge telescope proved very cumbersome, however, and most of his subsequent observations were made with a smaller, 20-foot focal length, telescope.

one of Herschel's telescope
Herschel's telescope

About 1800, Herschel discovered infrared radiation by passing sunlight through a prism and holding a thermometer just beyond the red end of the visible spectrum. The thermometer indicated a temperature increase and this led to Herschel's conclusion that there must be an invisible form of light.

In 1802, Herschel coined the word "asteroid" to describe the star-like appearance of the small moons of the giant planets and of the minor planets.

Herschel was made a Knight of the Royal Guelphic Order by the Prince Regent in 1816, entitling him to use the title "Sir." In 1820, he helped to found the Astronomical Society of London, which received a royal charter and became the Royal Astronomical Society in 1831.

William Herschel died at Slough, England, on August 25, 1822. He is buried at St. Laurence's Church, in Upton. His house in Bath, where he made many of his telescopes and first observed Uranus, is now home to the William Herschel Museum.

See Also

Bath, England
Caroline Herschel
King George III

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This page was last updated on 08/28/2018.