Daniel Kirkwood (September 27, 1814 – June 11, 1895) was an American
astronomer
An astronomer is a scientist in the field of astronomy who focuses their studies on a specific question or field outside the scope of Earth. They observe astronomical objects such as stars, planets, moons, comets and galaxies – in either ...
.
Kirkwood was born in
Harford County, Maryland to John and Agnes (née Hope) Kirkwood. He graduated in mathematics from the York County Academy in
York, Pennsylvania
York (Pennsylvania Dutch: ''Yarrick''), known as the White Rose City (after the symbol of the House of York), is the county seat of York County, Pennsylvania, United States. It is located in the south-central region of the state. The populatio ...
in 1838. After teaching there for five years, he became Principal of the Lancaster High School in
Lancaster, Pennsylvania, and after another five years he moved on to become Principal of the Pottsville Academy in
Pottsville, Pennsylvania
Pottsville is the county seat of Schuylkill County, Pennsylvania, United States. The population was 13,346 at the 2020 census, and is the principal city of the Pottsville, PA Micropolitan Statistical Area. The city lies along the west bank of th ...
. In 1851, he was elected as a member to the
American Philosophical Society
The American Philosophical Society (APS), founded in 1743 in Philadelphia, is a scholarly organization that promotes knowledge in the sciences and humanities through research, professional meetings, publications, library resources, and communit ...
. The same year he became Professor of Mathematics at
Delaware College
The University of Delaware (colloquially UD or Delaware) is a public land-grant research university located in Newark, Delaware. UD is the largest university in Delaware. It offers three associate's programs, 148 bachelor's programs, 121 mas ...
and in 1856 Professor of Mathematics at
Indiana University
Indiana University (IU) is a system of public universities in the U.S. state of Indiana.
Campuses
Indiana University has two core campuses, five regional campuses, and two regional centers under the administration of IUPUI.
*Indiana Universi ...
in
Bloomington, Indiana
Bloomington is a city in and the county seat of Monroe County in the central region of the U.S. state of Indiana. It is the seventh-largest city in Indiana and the fourth-largest outside the Indianapolis metropolitan area. According to the Mo ...
, where he stayed until his retirement in 1886, with the exception of two years, 1865–1867, at
Jefferson College in
Canonsburg, Pennsylvania
Canonsburg is a borough in Washington County, Pennsylvania, southwest of Pittsburgh. Canonsburg was laid out by Colonel John Canon in 1789 and incorporated in 1802. The population was 9,735 at the 2020 census. The town lies in a rich coal distr ...
.
Kirkwood's most significant contribution came from his study of
asteroid orbits. When arranging the then-growing number of discovered asteroids by their distance from the Sun, he noted several gaps,
[Kirkwood, Daniel (1866). "On the Theory of Meteors" in ''Proceedings of American Association for the Advancement of Science for 1866'', pp.8-14.] now named
Kirkwood gap
A Kirkwood gap is a gap or dip in the distribution of the semi-major axes (or equivalently of the orbital periods) of the orbits of main-belt asteroids. They correspond to the locations of orbital resonances with Jupiter.
For example, there a ...
s in his honor, and associated these gaps with
orbital resonance
In celestial mechanics, orbital resonance occurs when orbiting bodies exert regular, periodic gravitational influence on each other, usually because their orbital periods are related by a ratio of small integers. Most commonly, this relationsh ...
s with the orbit of
Jupiter
Jupiter is the fifth planet from the Sun and the largest in the Solar System. It is a gas giant with a mass more than two and a half times that of all the other planets in the Solar System combined, but slightly less than one-thousandth t ...
. Further, Kirkwood also suggested a similar dynamic was responsible for
Cassini Division in
Saturn's rings
The rings of Saturn are the most extensive ring system of any planet in the Solar System. They consist of countless small particles, ranging in size from micrometers to meters, that orbit around Saturn. The ring particles are made almost entire ...
, as the result of a
resonance
Resonance describes the phenomenon of increased amplitude that occurs when the frequency of an applied Periodic function, periodic force (or a Fourier analysis, Fourier component of it) is equal or close to a natural frequency of the system ...
with one of
Saturn's moons. In the same paper, he was the first to correctly posit that the material in
meteor showers is
comet
A comet is an icy, small Solar System body that, when passing close to the Sun, warms and begins to release gases, a process that is called outgassing. This produces a visible atmosphere or coma, and sometimes also a tail. These phenomena ...
ary debris.
Kirkwood also identified a pattern relating the distances of the
planet
A planet is a large, rounded astronomical body that is neither a star nor its remnant. The best available theory of planet formation is the nebular hypothesis, which posits that an interstellar cloud collapses out of a nebula to create a you ...
s to their rotation periods, which was called Kirkwood's Law. This discovery earned Kirkwood an international reputation among astronomers; he was dubbed "the American
Kepler
Johannes Kepler (; ; 27 December 1571 – 15 November 1630) was a German astronomer, mathematician, astrologer, natural philosopher and writer on music. He is a key figure in the 17th-century Scientific Revolution, best known for his laws o ...
" by
Sears Cook Walker
Sears Cook Walker (March 28, 1805 – January 30, 1853) was an American astronomer.
Born at Wilmington, Massachusetts son of Benjamin Walker and Susanna Cook, he graduated from Harvard University in 1825, he was a teacher till 1835, was an ...
, who claimed that Kirkwood's Law proved the widely held
Solar Nebula Theory. The "Law" has since become discredited as new measurements of planetary rotation periods have shown that the pattern doesn't hold.
In 1891, at age 77, he became a lecturer in astronomy at
Stanford University. He died in
Riverside, California
Riverside is a city in and the county seat of Riverside County, California, United States, in the Inland Empire metropolitan area. It is named for its location beside the Santa Ana River. It is the most populous city in the Inland Empire an ...
in 1895.
Altogether he wrote 129 publications, including three books. The asteroid was named
1578 Kirkwood
1578 Kirkwood, provisional designation , is a Hilda asteroid from the outermost regions of the asteroid belt, approximately 52 kilometers in diameter. It was discovered on 10 January 1951, by astronomers of the Indiana Asteroid Program at Goethe ...
in his honor and so was the lunar impact crater ''
Kirkwood'', as well as Indiana University's
Kirkwood Observatory
Kirkwood Observatory is an astronomical observatory owned and operated by Indiana University. It is located in Bloomington, Indiana, United States. It is named for Daniel Kirkwood (1814–1895) an astronomer and professor of mathematics at India ...
. He is buried in the Rose Hill Cemetery in
Bloomington, Indiana
Bloomington is a city in and the county seat of Monroe County in the central region of the U.S. state of Indiana. It is the seventh-largest city in Indiana and the fourth-largest outside the Indianapolis metropolitan area. According to the Mo ...
, where Kirkwood Avenue is named for him.
Kirkwood was a cousin of
Iowa
Iowa () is a state in the Midwestern region of the United States, bordered by the Mississippi River to the east and the Missouri River and Big Sioux River to the west. It is bordered by six states: Wisconsin to the northeast, Illinois to th ...
governor
Samuel Jordan Kirkwood
Samuel Jordan Kirkwood (December 20, 1813 – September 1, 1894) was an American politician who twice served as governor of Iowa, twice as a U.S. Senator from Iowa, and as the U.S. Secretary of the Interior.
Early life and career
Samuel Jordan ...
who became
United States Secretary of the Interior
The United States secretary of the interior is the head of the United States Department of the Interior. The secretary and the Department of the Interior are responsible for the management and conservation of most federal land along with natur ...
under President
James A. Garfield
James Abram Garfield (November 19, 1831 – September 19, 1881) was the 20th president of the United States, serving from March 4, 1881 until his death six months latertwo months after he was shot by an assassin. A lawyer and Civil War gene ...
and President
Chester A. Arthur
Chester Alan Arthur (October 5, 1829 – November 18, 1886) was an American lawyer and politician who served as the 21st president of the United States from 1881 to 1885. He previously served as the 20th vice president under President James ...
.
Further reading
*
Frank K. Edmondson,"Daniel Kirkwood: Dean of American Astronomers," ''
Mercury'' Magazine (publication of the
Astronomical Society of the Pacific), vol. 29, no. 3 (2000), pp. 26–33.
*J. Donald Fernie 1999,
The American Kepler" The New Scientist vol. 87, no. 5, pg. 398.
References
External links
*
*
*
"Daniel Kirkwood papers, 1864-1895"finding aid for the collection at the Indiana University Archives, Bloomington
{{DEFAULTSORT:Kirkwood, Daniel
1814 births
1895 deaths
American astronomers
Planetary scientists
Washington & Jefferson College faculty
Indiana University faculty
Presidents of the University of Delaware
People from Harford County, Maryland