Daniel Kirkwood

Daniel Kirkwood

Daniel Kirkwood (born September 27, 1814 in Hartford County , Maryland , † June 11, 1895 in Riverside , California ) was an American astronomer .

Life career

Kirkwood was born on a farm in Maryland and began teaching at the school when he was 19. He learned algebra himself by teaching his students with the help of a textbook. Eventually he studied at York County College, Pennsylvania , where he also taught after graduating in 1838.

In 1843 he became the head of Lancaster High School in Pennsylvania. Here he began to deal with astronomical subjects. Seven works were created, the second of which dealt with the asteroids on the occasion of the discovery of the 5th asteroid ( Astraea ) .

In August 1849 he drew international attention when he discovered a relationship between the periods of proper rotation of the planets and the radii of their orbits , which he called a mathematical analogy and which later became known as Kirkwood's analogy . Starting from the theory of Pierre-Simon Laplace about the origin of the solar system and looking for a law similar to the third Kepler law, only here for the periods of rotation of the planets, he set the number of revolutions of the planet per revolution around the sun with the diameter of its sphere of attraction in connection (the distance between the points at which two neighboring planets exert the same attraction force when they are in conjunction , for the outer and inner neighboring planets): ${\displaystyle n}$ ${\displaystyle D}$

${\displaystyle {\frac {n_{1}}{n_{2}}}=\left({\frac {D_{1}}{D_{2}}}\right)^{\frac {3}{2}}}$

In 1849, US Coastal Survey astronomer Sears Cook Walker presented the formula at the American Association for the Advancement of Science's annual meeting . The formula could be tested on Earth, Venus and Saturn and showed good agreement. This also meant that Laplace's nebula hypothesis gained more prestige again. At the same time, the formula supported the thesis already put forward by Kepler that there was once another planet between Mars and Jupiter (which Walker called Kirkwood ), in the area of ​​the asteroid belt, which form its remains. In 1850, Kirkwood's discovery was also celebrated in England at the British Association for the Advancement of Science meeting by David Brewster , by other astronomers such as Charles Piazzi Smyth (the Royal Astronomer of Scotland, who saw it as a numerical coincidence like Bode's Law ) and continental European astronomers like Heinrich Christian Schumacher , who printed a message about it in the Astronomische Nachrichten, the reception was rather cool.

In 1851 Kirkwood became a professor of mathematics at Delaware College and served there as president between 1854 and 1856. Also in 1851 he was elected a member of the American Philosophical Society .

In 1856, Kirkwood went to Indiana University , Bloomington, as a professor of mathematics . Here he continued to work in asteroid research and in 1861 made the proposal that the meteor showers could be the remains of a destroyed comet .

His most important achievement is the discovery of the gaps in the asteroid belt named after him , which he made in 1866, the so-called Kirkwood gaps .

The asteroid (1578) Kirkwood bears his name.

Web links

• English biography ( Memento of January 10, 2005 in the Internet Archive )
• Ronald L. Numbers The American Kepler: Daniel Kirkwood and his analogy , Journal for the History of Astronomy, Volume 4, 1973, pp. 13-21
• Publications by D. Kirkwood in the Astrophysics Data System
• Wm. W. Payne: Daniel Kirkwood. Popular Astronomy, Vol. 1 (1893), pp. 167–169 (short biography, English)
• J. Swain: Daniel Kirkwood. Publications of the Astronomical Society of the Pacific, Vol. 13 (1901), No. 80, p. 140 (obituary, English)

Individual evidence

1. ^ Member History: Daniel Kirkwood. American Philosophical Society, accessed October 24, 2018 .