Olbers

NAME:  Olbers, Heinrich Wilhelm Matthaus (known as Wilhelm)

ACHIEVEMENT(S):  Discovered the asteroids Pallas and Vesta and formulated a method for calculating the orbits of comets

NICKNAME/ALIAS:  None

DATE AND PLACE OF BIRTH:  October 11, 1758, Arbergen, (Bremen), Germany

DATE/PLACE OF DEATH/AGE AT DEATH:  March 2, 1840, Bremen, Germany.  Aged 81

DISCIPLINE:  Astronomer

FIELD:  Astronomy

LANGUAGE:  German

PARENTS:  Johann Jurgen Olbers; Anna Maria Vogt

SIBLINGS:  15

SPOUSE:  1) Dorothea Kohne.  2) Anna Adelheid Lurssen.

CHILDREN:  1) By Dorothea Kohne: Dorothea.  2)By Anna Lurssen: Georg Heinrich

EDUCATION:  Bremen Gymnasium; University of Gottingen

MAJOR WORK:

LIFE AND TIMES:

Though enroled in medicine at the University of Gottingen, Olbers studied astronomy on his own.  In 1779, he calculated the orbit of <calculated orbit of> Bode's* comet, and in 1780, discovered his own first comet. 

In his doctor's dissertation, "Changes in the Eye", Olbers applied mathematics to physiology to explain how the eye changes focus. After getting his medical degree in 1781, he specialized in ophthalmology, a new field.

After graduation, Olbers visited Vienna, spending his days in hospitals and his nights at the Vienna Observatory, observing <saw new planet of> William Herschel's* recently discovered planet Uranus. 

After a year, he set up a medical practice in Bremen, but kept up his astronomy, building a full conservatory in his house that included refractors, a reflector, a heliometer and three comet-seekers.  Able to get by on four hours sleep, he devoted his nights to astronomy.  In 1796, after 10 years of observing the skies, he discovered his second comet and calculated its parabolic orbit using a new method.

It had been assumed that when three observations of a comet had been obtained within a short period of time, the radius vector of the middle observation would divide the chord of the orbit of the comet from the first to the last observation in relation to the traversed time.  

Olbers established that this assumption could be applied with equal advantage to the three positions of the Earth in its orbit, and from this idea he worked out simple and easily calculated formulas. He sent his treatise to <published by> Zach*, director of the newly-founded observatory near Gotha, who used the method to compute the orbit of the comet of 1779, which had presented cause astronomers problems.  Zach was so pleased he oversaw publication of the treatise, which appeared in 1797.  It immediately established Olbers as a leading astronomer, and his method for calculating the orbit of comets was used throughout the 19th century.

In 1801, <work related to> Piazzi* discovered the first asteroid, Ceres, in the apparent "gap" (proposed in Bode's Law) between Mars and Jupiter, but was able to trace only a small arc of its orbit before it disappeared. 

At the time, astronomers lacked the means to compute an orbit from such a small arc as that provided by Piazzi.  But in Germany, astronomer <a pal of> Gauss* had been working on a new calculating method and made a stab at determining Ceres's orbit (using his “least squares” method:  see Gauss). 

Within days, using Gauss's calculations, Olbers located the asteroid, very near to where Gauss had said it would be.  Olbers sent his results to Gauss, marking the beginning of a lifelong friendship and collaboration.

In 1802, Olbers discovered a second asteroid, Pallas.  A third, Juno, was discovered by Karl Harding in 1804, and Olbers discovered Vesta in 1807.  The orbits of these bodies suggested to Olbers that they had a common point of origin and might be in fact be the broken-up remnants of a medium-sized planet that once orbited in the asteroid belt region.  In all, Olbers discovered five comets including,  in 1815, Olbers's Comet, which has an orbit of 72 years, similar to Halley's Comet.  He also calculated the orbits of 18 other comets.

In 1811, having noticed that comets consist of a star-like nucleus and a parabolic cloud of matter, Olbers formed the theory that the tail of a comet always points away from the Sun because it is matter expelled by the comet's nucleus and repelled by pressure from the Sun's radiation. 

In an 1823 paper, he proposed Olbers' Paradox (which influenced <influenced> Zollner* and was explained by American poet Edgar Allen <his Paradox explained by>Poe*), which deals with why the sky is dark at night. The Paradox states that if we accept the idea of an infinite, uniform Universe, the whole sky should be covered by stars shining as brightly as our Sun, but since space is not absolutely transparent, some interstellar matter (“dark matter”) absorbs enough starlight to dim the light of the stars, and they are seen as points against a dark sky.

In 1823, Olbers retired as a doctor, but continued his astronomical studies on comets, the influence of the Moon on the weather, the origin of meteorite showers, and the history of astronomy. 

In 1832, he predicted from observations of Biela's Comet that the Earth would pass through its tail.  The prediction caused much panic, but there were no catastrophic effects.  Olbers influenced and encouraged many young astronomers, most notably the young <influenced> Bessel*, who in 1804, approached Olbers with his calculation of the orbit of Halley's comet.

ASSESSMENT:  A pioneer astronomer.

EXTRA CONNECTIONS:  His work related to that of <work related to> Struve*

ONELINER: Wilhelm Olbers, calculator or planetary orbits

BIBLIOGRAPHY:

EB

DSB

Biographical Dictionary of Astronomers