William Herschel

Frederick William Herschel, English William Herschel (* November 15, 1738 in Hanover; † August 25, 1822 in Slough ) was a native of Germany British astronomer and musician.


Herschel's father Isaac was a military musician; the son came with 14 years as an oboist in the short - Hanoverian Foot Guards. After the occupation of Hanover in 1757 by French troops, he escaped to England ( which was then connected to his homeland Hanover in personal union ). There he worked as a music teacher, composer and organist. Herschel worked as a music teacher in Leeds and then as an organist in Halifax. In 1766 he was music director in Bath. Through the study of mathematical music theory suggested that he was concerned with mathematics as well as the construction and sale of astronomical instruments. With the study of astronomical works his interest grew in astronomy, which extended not only to the observations of the moon, planets and comets for him. Rather, he wanted to study the properties of the fixed stars, and even create a complete listing of all the visible stars and nebulae. However, your standard 1770 telescopes and reflecting telescopes were not technically capable. So he began even to build reflecting telescopes, which he succeeded after initial failures. From 1766 he made numerous telescopes with ever- increasing diameter to (and therefore higher resolution ). In his observations, Herschel was supported by his brother Alexander and his sister Caroline.

Suddenly became famous Herschel, in 1781 when he discovered a new object in the solar system: the planet Uranus. He was elected a Fellow of the Royal Society of London. King George III. told him to an annual fee. So he was able to completely his hobby, astronomy, turn. The Herschel moved from Bath to Slough on. Herschel set forth in the following period telescopes not only for their own use, but also for the improvement of its revenue. In 1788 he married Mary Pitt, widow of one of his neighbors. His only son, John Frederick William Herschel, was born in 1792. In 1816, he was by the Prince Regent, the future King George IV knighted. 1817 Knights Cross of the Order of Guelph, he was awarded. In 1820 he was elected the first President of the Royal Astronomical Society, who had his son, who was also an important astronomer, founded by Charles Babbage and others. Lived in Slough and he worked until his death in 1822.

Herschel was buried in St. Laurence 's Chapel in Upton, Slough. On his grave stone of the Latin sentence Caelorum is perrupit claustra ( "He broke through the boundaries of the sky ").

1935, the lunar crater Herschel was named after him. In 1973, the Mars crater Herschel was jointly by him and his son, Sir John Herschel, was baptized. 1982 with the appointment of a third crater, the Mimaskrater Herschel, after him a special honor it was to be divided: The largest crater of this Saturnian moon bares the name of the discoverer of the moon.


Uranus, moons, rings and fog

Since prehistoric times, people knew only the five planets Mercury, Venus, Mars, Jupiter and Saturn. March 13, 1781 Herschel discovered in a systematic sky survey with a self-made reflecting telescope an object that struck him through his clearly areal appearance. He first thought of a comet and named it Georgium sidus (Georg star ). After it was found that it ran as the known planets on a nearly circular orbit, it was called Uranus. With this discovery, the extent of the solar system had grown to double that. After the two moons Titania and Oberon (both 1787) Herschel discovered in 1797 already, the ring system of Uranus, which was however dismissed until its re- discovery in 1977 as a mistake. The sightings of Saturn's moons Mimas and Enceladus to his credit.

Herschel's interest, however, lay with the misty sky objects. Charles Messier had 1780/81 published a catalog of 103 non- point-like ( " foggy " ) appearing objects; the experts did not agree, whether it be negotiated in each case by countless stars or to luminous clouds or liquids. From autumn 1782 to Herschel was looking specifically for other objects of this type (up to 1802). With its superior device he soon found that he was able to release more of the "fog" in single stars. He suspected that the other objects are star clusters, and the only reason could not be resolved because they are much further away - and hence much larger - than were previously thought. This presumption expressed in 1785 has proven to be correct in principle. However, Herschel could not know that it was fundamentally different types: real glowing gas clouds ( like the Orion Nebula ), star clusters (like the Pleiades or M13) and galaxies (such as the Andromeda Galaxy ).

Fog classification and Milky statistics

Herschel led first a classification of these objects. He distinguished them after the apparent brightness, size, regularity of form and concentration towards the center. During his studies, he developed a theory of the formation of star clusters: The gravity could have given rise to the time of loose clusters densely packed systems. He introduced the concept of development (or evolution) in astronomy: The starry sky was now no longer eternal and unchanging. Herschel became the founder of the cognitive area cosmology.

As he watched a fixed star with surrounding cloud in 1790, he revised his earlier view. He thought it was now possible that all the stars would have been contracted under the influence of gravity from a kind of cloud of gas or liquid.

Also, statistics and probability considerations, he used the first astronomer: He found that a piece of the Milky Way, 15 ° long and 2 ° wide, contains more than 50,000 clearly recognizable stars. From the distribution of the fixed stars he sought the shape of the Milky Way derived. He came to the conclusion that it was a lens-shaped collection of stars. Since he assumed all the fixed stars have the same absolute magnitude, he believed he could infer from the apparent magnitude to the distance. This approach proved to be wrong. From Herschel, the first attempts to determine the motion of the solar system in space come - a work which, however, only has been successfully commissioned by Argelander, inter alia, with sharper telescopes in attack.

He also noted that not all double stars could be located just happened so ( visual double stars ). It had rather be a significant number that are bound together by gravity (physical double stars ). He was able to observe the circular motion of some of these star pairs, and began systematic comparison of the brightness component.

Double stars and light spectrum

Over time, he created a catalog of nebulous objects with more than 2500 entries ( " Herschel catalog "), and a catalog of 848 double stars. Without the selfless help of his sister, Caroline, these catalogs would not be told.

Although his particular interest was the life-long fixed stars, he did not neglect the objects of the solar system: he discovered the Uranus moons Titania and Oberon, and Saturn's moons Mimas and Enceladus - which he was the only moon explorers of the 18th century. He determined at Saturn the rotation period and showed changes after the Mars seasonal. From the observation of the Lomonosov effect he concluded that Venus must have an atmosphere. Lomonosov had this already suspected in 1761, but not published.

Herschel discovered in 1800, the infrared radiation by directing sunlight through a prism and beyond the red end of the visible spectrum installed a thermometer. The temperature rose in this area, and Herschel concluded that there must be effective an invisible form of energy.

Herschel's observations were only possible through the hitherto extraordinary light output of its telescopes, however, hampered by their lack of sharpness. He was an exceptionally talented and tireless observer; his solutions were (sometimes too ) boldly, but always leading the way.

Sunspots and Climate

Herschel was the first researcher influence of the sun on the air this week. He compared historical observations of sunspots and as an indicator of the climate development in wheat prices.

'The result of this review of the foregoing five periods is, that, from the price of wheat, It Seems probable did some temporary scarcity or defect of vegetation Has gene rally taken place, When the sun HAS BEEN without Those appearances Which We surmise to be symptoms of a copious emission of light and heat. "

The thesis of a connection between climate and sunspots was very controversial to Herschel times and this is even today.

Herschel Telescope

Herschel invented an alternative to the lateral eye of the Newtonian telescope, because its mirror it were large enough. These writes Meyers encyclopedia 1885:

And therefore the induced light from him loss avoided by a simple trick: " When the giant telescopes of Herschel and Lord Rosse, whose levels were 1-2 m in diameter, was such a second mirrors [ Fangspiegel note]. The concave mirror (ss, Figure 5 ) is in fact a little inclined to the axis of the tube, so that the little picture comes close to lie at the edge of the mirror and can be viewed there by an ocular o. It certainly occurs, the head of the observer in part before the opening of the tube, but this is at the large diameter of the mirror of little consequence. Herschel called his instrument front view telescop, ie front sight telescope. "

The method presupposes a relatively low aperture ratio ( mirror diameter / focal length). The tilt of the primary mirror to the optical axis of the telescope would otherwise lead to severe aberrations in difficulty (see Schiefspiegler ).

From the variety of telescopes Herschel built and used, are particularly worthy of mention:

  • The planet Uranus discovered Herschel telescope with a mirror of 6 inches (about 15 cm ) in diameter and 7 feet ( about 210 cm) focal length.
  • For his fog catalog he used mainly a device with a 18.7 -inch ( 47.5 cm) mirror and 20 feet (6.1 m) focal length (from 1783).
  • His biggest telescope ( see figure) was built in 1789 under his direction and had a mirror diameter of 48 inches (122 cm) and a length of 40 feet (12 m). The aperture ratio therefore stood at about 1:10. It was not until two generations later surpassed by Lord Rosses "Leviathan". The 48-inch telescope was destroyed by a storm in 1839.

Herschel built exclusively mirror telescopes. Your mirrors were cast from a metal alloy ( speculum ), and often had to be polished as they anliefen easily.

Herschel as a musician and composer

Herschel played alongside cello and oboe and organ. He composed many pieces of music, including 24 symphonies and many concertos and church music. Except for a few oboe concertos and symphonies, which were recorded in 2003, his music has been forgotten.

Writings (selection )

  • Description of a Forty -feet Reflecting Telescope. Phil Trans R. Soc. Lond. 1 January 1795 vol. 85347-409 ( doi: 10.1098/rstl.1795.0021 and fulltext )
  • Account of a Comet. Phil Trans R. Soc. Lond. January 1, 1781 71:492-501 ( doi: 10.1098/rstl.1781.0056 and fulltext )
  • An Account of the Discovery of Two Satellites Revolving Round the Georgian Planet. Phil Trans R. Soc. Lond. January 1, 1787 77:125-129 ( doi: 10.1098/rstl.1787.0016 and fulltext )
  • Account of the Discovery of a Sixth and Seventh Satellite of the Planet Saturn; With Remarks on the Construction of Its Ring, Its Atmosphere, Its rotation on to Axis, and Its Spheroidical Figure. Phil Trans R. Soc. Lond. January 1, 1790 80:1-20 ( doi: 10.1098/rstl.1790.0001 and fulltext )
  • About the construction of the heavens. Treatises on the structure of the universe and the evolution of celestial bodies from 1784 to 1814. Edited by Jürgen Hamel. Harri German Verlag, Frankfurt am Main 2001 ( = Ostwald classics of the exact sciences, Volume 288 ). ISBN 3-8171-3288-3.