Herschel Program – Friedrich Wilhelm Herschel

Herschel Program – Friedrich Wilhelm Herschel


Famous Portrait of Dr. Herschel

Friedrich Wilhelm Herschel, better known as Sir William Herschel, was born in Hanover, Germany on November 15, 1738.

Music was an important part of his upbringing, this became evident when he became a bandboy with the Hanoverian Guards. Later on he was either inducted or a volunteer in the military where he served only briefly. Due to his delicate health he discovered he was unsuited for army life and his father helped him to leave Germany for England in 1757 where he took up residence. He was later reunited with his brother, Alexander, and his sister Caroline who joined him in England.

His career in music began when he was employed as a military bandmaster, then as a music teacher and organist at the Octagon Chapel in Bath, England. He also composed and gave concerts. He was, in fact, a very successful musician. However, Herschel developed an avid interest in astronomy and this became his first love. He rented a small reflecting telescope, but this only whetted his appetite to own his own, larger telescope. Since he didn’t have enough money to buy one, he contrived to build it with the help of Alexander and Caroline. This eventually led to the construction of his largest telescope, a 48-inch reflector which he build with a 4,000 pound grant from King George III. However, most of his recorded observations were made with his 20-foot reflecting telescope. Because of his great zeal and methodical nature, William Herschel became one of the most notable observers in the history of astronomy. His systematic survey of the sky was one of the most important of his accomplishments.

Herschel's 20-foot telescopeOn March 13, 1781, while scanning the skies with a 7-inch reflecting telescope, he observed an unusual object; it presented an extended disk-like shape. Herschel thought he had discovered a comet. He continued his observations, and calculations for months, discovering the orbit lay well beyond the orbit of Saturn and was fairly circular. Herschel’s “Comet” was in fact a planet. Different names were suggested, including his own name, “Herschel”. He, however, wanted to call the new planet “Georgium Sidus,” after his new patron, George III. This name, however, did not find favor with the astronomical community. It was eventually named Uranus after the mythological god of the skies.

Herschel was granted a pension of 200 pounds a year and knighted by King George III, who also made him “King’s Astronomer”. Receiving a pension enabled Herschel to devote full time to astronomy.

The instruments Herschel had lacked clock drives to keep them trained on the moving sky, so the method he used was to direct his telescope to a point on the meridian and watch what crossed the field of view. Since Herschel had to stand on a ladder to do his observing, he would call out descriptions of whatever he saw of interest to his sister Caroline at the foot of the ladder. She would then record the information and time. By using this method he was able to observe objects in a thin east-west strip of sky. As the nights progressed, he would change the position of the telescope to an elevation higher or lower than the previous night. This enabled him to observe another strip of sky. They eventually were able to observe all the sky visible in Great Britain.

During the course of his observations, he discovered large quantities of faint patches of light (nebulae) and methodically catalogue these objects. Herschel’s son John took his father’s instrument to South Africa where he was able to survey the southern skies. John Herschel in 1864 published a catalog. Of the 5,097 objects, 4,630 of them were discovered by William and his son John Herschel. The catalog was called “The General Catalogue of Nebulae.”

In 1888 this catalogue was revised and enlarged by L.E. Dreyer. It now contained 7,840 nebulae and clusters. After its revision it was call the “New General Catalogue”. Most non-stellar objects are still known by their new General Catalogue (NGC) numbers.

Herschel’s observations and discoveries are numerous. He observed sunspots and confirmed the gaseous nature of the sun. He discovered not only the planet Uranus, but two of its moons, and also two of Jupiter’s moons.

His principal works were on stars. Two discoveries of primary importance is the movement of the solar system through space and the evidence that binary stars move around a common center of gravity. He discovered nearly 1,000 double stars.

In 1785 he brought out the disc theory of the stellar system, anticipating the shape of our own galaxy. Herschel believed that all nebulae are clusters of stars which he called island nebulae.

He also discovered the infrared range of sunlight. Sir William Herschel died in Slough, England on August 25, 1822.

-Peggy Taylor & Sara Saey

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