Daniel Kirkwood
Encyclopedia
Daniel Kirkwood was an American astronomer
.
Born in Harford County, Maryland
, he was graduated in mathematics
from the York County Academy in York, Pennsylvania
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
. In 1851 he became Professor of Mathematics at Delaware College
and in 1856 Professor of Mathematics at Indiana University
in Bloomington, Indiana
, where he stayed until his retirement in 1886, with the exception of two years, 1865–1867, at Jefferson College in Canonsburg, Pennsylvania
.
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, now named Kirkwood gap
s in his honor, and associated these gaps with orbital resonance
s with the orbit of Jupiter
. Further, Kirkwood also suggested a similar dynamic was responsible for Cassini Division in Saturn's rings
, as the result of a resonance
with one of Saturn's moons. In the same paper, he was the first to correctly posit that the material in meteor shower
s is comet
ary debris.
Kirkwood also identified a pattern relating the distances of the planet
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
" by Sears Cook Walker
, 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
in 1895.
Altogether he wrote 129 publications, including three books. The asteroid 1951 AT was named 1578 Kirkwood
in his honor and so was the lunar impact crater Kirkwood
, as well as Indiana University's Kirkwood Observatory
. He is buried in the Rose Hill Cemetery in Bloomington, Indiana
, where Kirkwood Avenue is named for him.
Kirkwood was a cousin of Iowa
governor Samuel Jordan Kirkwood
who became United States Secretary of the Interior
under President James A. Garfield and President Chester A. Arthur
.
Astronomer
An astronomer is a scientist who studies celestial bodies such as planets, stars and galaxies.Historically, astronomy was more concerned with the classification and description of phenomena in the sky, while astrophysics attempted to explain these phenomena and the differences between them using...
.
Born in Harford County, Maryland
Harford County, Maryland
Harford County is a county in the U.S. state of Maryland. In 2010, its population was 244,826. Its county seat is Bel Air. Harford County forms part of the Baltimore-Washington Metropolitan Area.-History:...
, he was graduated in mathematics
Mathematics
Mathematics is the study of quantity, space, structure, and change. Mathematicians seek out patterns and formulate new conjectures. Mathematicians resolve the truth or falsity of conjectures by mathematical proofs, which are arguments sufficient to convince other mathematicians of their validity...
from the York County Academy in York, Pennsylvania
York, Pennsylvania
York, known as the White Rose City , is a city located in York County, Pennsylvania, United States which is in the South Central region of the state. The population within the city limits was 43,718 at the 2010 census, which was a 7.0% increase from the 2000 count of 40,862...
in 1838. After teaching there for five years, he became Principal of the Lancaster High School in Lancaster, Pennsylvania
Lancaster, Pennsylvania
Lancaster is a city in the south-central part of the Commonwealth of Pennsylvania. It is the county seat of Lancaster County and one of the older inland cities in the United States, . With a population of 59,322, it ranks eighth in population among Pennsylvania's cities...
, and after another five years he moved on to become Principal of the Pottsville Academy in Pottsville, Pennsylvania
Pottsville, Pennsylvania
Pottsville is the only city in and the county seat of Schuylkill County, Pennsylvania, United States. The population was 15,549 at the 2000 census. The city lies along the west bank of the Schuylkill River, north-west of Philadelphia...
. In 1851 he became Professor of Mathematics at Delaware College
University of Delaware
The university is organized into seven colleges:* College of Agriculture and Natural Resources* College of Arts and Sciences* Alfred Lerner College of Business and Economics* College of Earth, Ocean and Environment* College of Education and Human Development...
and in 1856 Professor of Mathematics at Indiana University
Indiana University Bloomington
Indiana University Bloomington is a public research university located in Bloomington, Indiana, in the United States. IU Bloomington is the flagship campus of the Indiana University system. Being the flagship campus, IU Bloomington is often referred to simply as IU or Indiana...
in Bloomington, Indiana
Bloomington, Indiana
Bloomington is a city in and the county seat of Monroe County in the southern region of the U.S. state of Indiana. The population was 80,405 at the 2010 census....
, where he stayed until his retirement in 1886, with the exception of two years, 1865–1867, at Jefferson College in Canonsburg, Pennsylvania
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....
.
Kirkwood's most significant contribution came from his study of asteroid
Asteroid
Asteroids are a class of small Solar System bodies in orbit around the Sun. They have also been called planetoids, especially the larger ones...
orbits. When arranging the then-growing number of discovered asteroids by their distance from the Sun, he noted several gaps, now named Kirkwood gap
Kirkwood gap
A Kirkwood gap is a gap or dip in the distribution of main-belt asteroids with semi-major axis , as seen in the histogram below...
s in his honor, and associated these gaps with orbital resonance
Orbital resonance
In celestial mechanics, an orbital resonance occurs when two orbiting bodies exert a regular, periodic gravitational influence on each other, usually due to their orbital periods being related by a ratio of two small integers. Orbital resonances greatly enhance the mutual gravitational influence of...
s with the orbit of Jupiter
Jupiter
Jupiter is the fifth planet from the Sun and the largest planet within the Solar System. It is a gas giant with mass one-thousandth that of the Sun but is two and a half times the mass of all the other planets in our Solar System combined. Jupiter is classified as a gas giant along with Saturn,...
. Further, Kirkwood also suggested a similar dynamic was responsible for Cassini Division in Saturn's rings
Rings of Saturn
The rings of Saturn are the most extensive planetary ring system of any planet in the Solar System. They consist of countless small particles, ranging in size from micrometres to metres, that form clumps that in turn orbit about Saturn...
, as the result of a resonance
Orbital resonance
In celestial mechanics, an orbital resonance occurs when two orbiting bodies exert a regular, periodic gravitational influence on each other, usually due to their orbital periods being related by a ratio of two small integers. Orbital resonances greatly enhance the mutual gravitational influence of...
with one of Saturn's moons. In the same paper, he was the first to correctly posit that the material in meteor shower
Meteor shower
A meteor shower is a celestial event in which a number of meteors are observed to radiate from one point in the night sky. These meteors are caused by streams of cosmic debris called meteoroids entering Earth's atmosphere at extremely high speeds on parallel trajectories. Most meteors are smaller...
s is comet
Comet
A comet is an icy small Solar System body that, when close enough to the Sun, displays a visible coma and sometimes also a tail. These phenomena are both due to the effects of solar radiation and the solar wind upon the nucleus of the comet...
ary debris.
Kirkwood also identified a pattern relating the distances of the planet
Planet
A planet is a celestial body orbiting a star or stellar remnant that is massive enough to be rounded by its own gravity, is not massive enough to cause thermonuclear fusion, and has cleared its neighbouring region of planetesimals.The term planet is ancient, with ties to history, science,...
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
Johannes Kepler was a German mathematician, astronomer and astrologer. A key figure in the 17th century scientific revolution, he is best known for his eponymous laws of planetary motion, codified by later astronomers, based on his works Astronomia nova, Harmonices Mundi, and Epitome of Copernican...
" by Sears Cook Walker
Sears Cook Walker
Sears Cook Walker 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 actuary in 1835-1845 for the Pennsylvania Company for Insurance on Lives and Granting Annuities,...
, who claimed that Kirkwood's Law proved the widely held Solar Nebula Theory
Solar nebula
In cosmogony, the nebular hypothesis is the most widely accepted model explaining the formation and evolution of the Solar System. There is evidence that it was first proposed in 1734 by Emanuel Swedenborg. Originally applied only to our own Solar System, this method of planetary system formation...
. 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
Stanford University
The Leland Stanford Junior University, commonly referred to as Stanford University or Stanford, is a private research university on an campus located near Palo Alto, California. It is situated in the northwestern Santa Clara Valley on the San Francisco Peninsula, approximately northwest of San...
. He died in Riverside, California
Riverside, California
Riverside is a city in Riverside County, California, United States, and the county seat of the eponymous county. Named for its location beside the Santa Ana River, it is the largest city in the Riverside-San Bernardino-Ontario metropolitan area of Southern California, 4th largest inland California...
in 1895.
Altogether he wrote 129 publications, including three books. The asteroid 1951 AT was named 1578 Kirkwood
1578 Kirkwood
1578 Kirkwood, also known as 1944 DF, 1949 TF, 1951 AT and 1952 FK, is an asteroid which was discovered January 10, 1951 at Goethe Link Observatory near Brooklyn, Indiana by the Indiana Asteroid Program. This program was conceived and directed by Frank K. Edmondson of Indiana University. The...
in his honor and so was the lunar impact crater Kirkwood
Kirkwood (crater)
Kirkwood is a well-formed lunar impact crater that is located on the far side of the Moon, on the northern hemisphere. It lies just to the northeast of the crater Sommerfeld, and Hippocrates is located to the east-northeast....
, as well as Indiana University's Kirkwood Observatory
Kirkwood Observatory
Kirkwood Observatory is an astronomical observatory owned and operated by Indiana University. It is located in Bloomington, Indiana . It is named for Daniel Kirkwood an astronomer and professor of mathematics at Indiana University who discovered the divisions of the asteroid belt known as the...
. He is buried in the Rose Hill Cemetery in Bloomington, Indiana
Bloomington, Indiana
Bloomington is a city in and the county seat of Monroe County in the southern region of the U.S. state of Indiana. The population was 80,405 at the 2010 census....
, where Kirkwood Avenue is named for him.
Kirkwood was a cousin of Iowa
Iowa
Iowa is a state located in the Midwestern United States, an area often referred to as the "American Heartland". It derives its name from the Ioway people, one of the many American Indian tribes that occupied the state at the time of European exploration. Iowa was a part of the French colony of New...
governor Samuel Jordan Kirkwood
Samuel J. Kirkwood
Samuel Jordan Kirkwood , was an American politician best known as Iowa's American Civil War Governor. He also served in the U.S. Senate and as U.S. Secretary of the Interior.-Early life and career:...
who became United States Secretary of the Interior
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 US Department of the Interior should not be confused with the concept of Ministries of the Interior as used in other countries...
under President James A. Garfield and President Chester A. Arthur
Chester A. Arthur
Chester Alan Arthur was the 21st President of the United States . Becoming President after the assassination of President James A. Garfield, Arthur struggled to overcome suspicions of his beginnings as a politician from the New York City Republican machine, succeeding at that task by embracing...
.
See also
- Frank K. EdmondsonFrank K. EdmondsonFrank K. Edmondson was an American astronomer.-Life and career:Edmondson was born in Milwaukee, Wisconsin and grew up in Seymour, Indiana...
, "Daniel Kirkwood: Dean of American Astronomers," MercuryMercury (magazine)Mercury is a science magazine that features articles and columns about astronomy for a general audience. It is the bi-monthly magazine of the Astronomical Society of the Pacific and was first published in 1972....
Magazine (publication of the Astronomical Society of the PacificAstronomical Society of the PacificThe Astronomical Society of the Pacific is a scientific and educational organization, founded in San Francisco on February 7, 1889. Its name derives from its origins on the Pacific Coast, but today it has members all over the country and the world...
), vol. 29, no. 3 (2000), pp. 26–33.
- J. Donald Fernie 1999, "The American Kepler," The New Scientist vol. 87, no. 5, pg. 398.